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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Oncol.</journal-id>
<journal-title>Frontiers in Oncology</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Oncol.</abbrev-journal-title>
<issn pub-type="epub">2234-943X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fonc.2025.1618619</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Oncology</subject>
<subj-group>
<subject>Case Report</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Adenocarcinoma and squamous cell carcinoma in the same lobe of the lung with adenocarcinoma metastasis in the lymph nodes: a case report and literature review</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" equal-contrib="yes">
<name>
<surname>Li</surname>
<given-names>Chun-Sen</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="author-notes" rid="fn003">
<sup>&#x2020;</sup>
</xref>
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</contrib>
<contrib contrib-type="author" equal-contrib="yes">
<name>
<surname>Zou</surname>
<given-names>Yun-Xuan</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="author-notes" rid="fn003">
<sup>&#x2020;</sup>
</xref>
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</contrib>
<contrib contrib-type="author">
<name>
<surname>Wang</surname>
<given-names>Chun-Yan</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
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</contrib>
<contrib contrib-type="author">
<name>
<surname>Xu</surname>
<given-names>Guo-Dong</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
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</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Yang</surname>
<given-names>Mai-Qing</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="author-notes" rid="fn001">
<sup>*</sup>
</xref>
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<aff id="aff1">
<sup>1</sup>
<institution>Department of Pathology, Weifang People&#x2019;s Hospital (First Affiliated Hospital of Shandong Second Medical University)</institution>, <addr-line>Weifang, Shandong</addr-line>,&#xa0;<country>China</country>
</aff>
<aff id="aff2">
<sup>2</sup>
<institution>Department of Anesthesiology, Weifang People&#x2019;s Hospital (First Affiliated Hospital of Shandong Second Medical University)</institution>, <addr-line>Weifang, Shandong</addr-line>,&#xa0;<country>China</country>
</aff>
<aff id="aff3">
<sup>3</sup>
<institution>Department of Family Planning, Weifang People&#x2019;s Hospital (First Affiliated Hospital of Shandong Second Medical University)</institution>, <addr-line>Weifang, Shandong</addr-line>,&#xa0;<country>China</country>
</aff>
<author-notes>
<fn fn-type="edited-by">
<p>Edited by: Natsuo Tomita, Nagoya City University, Japan</p>
</fn>
<fn fn-type="edited-by">
<p>Reviewed by: Fengbo Huang, Zhejiang University, China</p>
<p>Dalibor Jovanovic, University of Kragujevac, Serbia</p>
</fn>
<fn fn-type="corresp" id="fn001">
<p>*Correspondence: Mai-Qing Yang, <email xlink:href="mailto:qqq387@163.com">qqq387@163.com</email>
</p>
</fn>
<fn fn-type="equal" id="fn003">
<p>&#x2020;These authors have contributed equally to this work</p>
</fn>
</author-notes>
<pub-date pub-type="epub">
<day>17</day>
<month>07</month>
<year>2025</year>
</pub-date>
<pub-date pub-type="collection">
<year>2025</year>
</pub-date>
<volume>15</volume>
<elocation-id>1618619</elocation-id>
<history>
<date date-type="received">
<day>26</day>
<month>04</month>
<year>2025</year>
</date>
<date date-type="accepted">
<day>30</day>
<month>06</month>
<year>2025</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#xa9; 2025 Li, Zou, Wang, Xu and Yang</copyright-statement>
<copyright-year>2025</copyright-year>
<copyright-holder>Li, Zou, Wang, Xu and Yang</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/">
<p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p>
</license>
</permissions>
<abstract>
<p>Adenocarcinoma and squamous cell carcinoma (SCC) of the same lobe of the lung is relatively rare. A 57-year-old man was admitted to Weifang People&#x2019;s Hospital (Weifang, China) with blood streaks in sputum and had masses in the lung. Based on clinical, imaging, and pathological findings, the patient was diagnosed with primary adenocarcinoma and SCC in the same lobe of the right lung, with adenocarcinoma metastasis to the lymph nodes. Few reports have described the synchronous occurrence of adenocarcinoma and SCC in the same lobe. Thoracoscopic resection of the lower lobes of the right lung and mediastinal lymph node dissection were performed. Surgical resection and postoperative chemotherapy have superior effects. The misdiagnosis of this tumor as other types of tumor must be prevented. Immunohistochemical features can be useful for the diagnosis of primary adenocarcinoma and SCC.</p>
</abstract>
<kwd-group>
<kwd>adenocarcinoma</kwd>
<kwd>squamous cell carcinoma</kwd>
<kwd>lung</kwd>
<kwd>immunohistochemical</kwd>
<kwd>diagnosis</kwd>
</kwd-group>
<counts>
<fig-count count="3"/>
<table-count count="1"/>
<equation-count count="0"/>
<ref-count count="37"/>
<page-count count="7"/>
<word-count count="2564"/>
</counts>
<custom-meta-wrap>
<custom-meta>
<meta-name>section-in-acceptance</meta-name>
<meta-value>Thoracic Oncology</meta-value>
</custom-meta>
</custom-meta-wrap>
</article-meta>
</front>
<body>
<sec id="s1" sec-type="intro">
<label>1</label>
<title>Introduction</title>
<p>Synchronous multiple primary lung cancer (sMPLC) is a special type of lung cancer characterized by the simultaneous identification of &#x2265; 2 primary tumors in the ipsilateral or contralateral lungs (<xref ref-type="bibr" rid="B1">1</xref>). The incidence of sMPLC ranges from 0.2&#x2013;20% in lung cancer (<xref ref-type="bibr" rid="B1">1</xref>&#x2013;<xref ref-type="bibr" rid="B4">4</xref>). Most of these tumors have the same histological type (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B5">5</xref>). Owing to the increase in detection rates, the proportion of sMPLC in lung cancer and five&#x2010;year survival rate are increasing, whereas postoperative mortality is decreasing gradually (<xref ref-type="bibr" rid="B1">1</xref>, <xref ref-type="bibr" rid="B6">6</xref>&#x2013;<xref ref-type="bibr" rid="B8">8</xref>). The clinical diagnosis of MPLC is predominantly based on the Martini-Melamed diagnostic criteria, which primarily rely on tumor location, histologic features, presence or absence of carcinoma <italic>in situ</italic>, and other characteristics (<xref ref-type="bibr" rid="B9">9</xref>). The American College of Chest Physicians (ACCP) and the International Association for the Study of Lung Cancer (IASLC) proposed updated diagnostic criteria (<xref ref-type="bibr" rid="B10">10</xref>). The 2016 IASLC criterion provided a more detailed description of MPLC diagnostic criteria, incorporating the Comprehensive Histologic Assessment (CHA) process (<xref ref-type="bibr" rid="B11">11</xref>). This paper reports an unusual case of synchronous adenocarcinoma and squamous cell carcinoma (SCC) in the same lobe of the lung with adenocarcinoma metastasis to the lymph nodes to strengthen our understanding of this disease. Knowingly, including the present case, only six patients with primary synchronous occurrence of adenocarcinoma and SCC in the same lobe have been reported (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B12">12</xref>&#x2013;<xref ref-type="bibr" rid="B14">14</xref>).</p>
</sec>
<sec id="s2">
<label>2</label>
<title>Case presentation</title>
<sec id="s2_1">
<label>2.1</label>
<title>Clinical history</title>
<p>A 57-year-old man was admitted to our hospital for further treatment and presented with blood streaks in sputum for &gt; 50 days. With many years smoking history of smoking approximately 40 cigarettes daily. The patient had no additional illness and was previously in good health. Personal history, family histories, medication history, social history, and allergy history were negative. Pulmonary function test is normal. Computed tomography (CT) evaluation showed a nodule in the posterior basal segment of the lower lobe of the right lung, approximately 3.1 cm &#xd7; 2.6 cm in size. Another nodule was observed in the medial basal segment of the lower lobe of the right lung, approximately 2.6 cm &#xd7; 2.3 cm in size. The mediastinum was centered and enlarged lymph node shadows were visible. No pleural effusion or thickening was observed on either side of the pleura (<xref ref-type="fig" rid="f1">
<bold>Figure&#xa0;1</bold>
</xref>). Blood SSC antigen (SCCA) (2.97 ng/mL) was slightly higher than normal (0&#x2013;2.5 ng/mL). Carcinoembryonic antigen (CEA) (1.33 ng/mL [0&#x2013;4.5 ng/mL]) and neuron-specific enolase (NSE) (13.23 ng/mL [0&#x2013;16.5 ng/mL]) were normal. The preoperative diagnosis was right lower-lobe lung cancer. Thoracoscopic resection of the lower lobe of the right lung was performed. Perioperatively, resected lung specimens were collected to prepare frozen sections for pathological evaluation. The diagnosis was &#x201c;two places of non-small cell lung cancer (NSCLC), depending on routine paraffin sections and immunohistochemical identification and classification after the operation.&#x201d; Subsequently, extended dissection of the mediastinal lymph nodes was performed.</p>
<fig id="f1" position="float">
<label>Figure&#xa0;1</label>
<caption>
<p>Chest computed tomography. Computed tomography shows a nodule in the posterior basal segment of the lower lobe of the right lung, approximately 3.1 cm &#xd7; 2.6 cm in size (nodule 1, yellow arrow). Another nodule is seen in the medial basal segment of the lower lobe of the right lung, approximately 2.6 cm &#xd7; 2.3 cm in size (nodule 2, red arrow). <bold>(A, B)</bold> Sagittal screenshot. <bold>(C, D)</bold> Axis position screenshot of nodule 1. <bold>(E, F)</bold> Axis position screenshot of nodule 2.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fonc-15-1618619-g001.tif">
<alt-text content-type="machine-generated">CT scans showing the chest region in both sagittal and axial views, labeled A to F. Arrows indicate specific areas of interest. Panels A and B highlight regions with red and yellow arrows. Panels C and D display axial views with yellow arrows pointing to distinct features. Panels E and F also show axial views with red arrows marking areas within the lung region.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s2_2">
<label>2.2</label>
<title>Immunohistochemical staining</title>
<p>The specimens were fixed with 10% neutral-buffered formalin, embedded in paraffin blocks, and cut into 4 &#x3bc;m thick sections. The sections were stained with hematoxylin and eosin (HE) for histological assessment. Tumor sections were immunostained with ready-to-use primary antibodies against cytokeratin 7 (CK7, Catalog Number: MAB-0828), TTF-1 (thyroid transcription factor-1, Catalog Number: MAB-0677), napsin A (Catalog Number: MAB-0704), CK5/6 (Catalog Number: RMA-1144), P40 (Catalog Number: RMA-1006), and Ki-67 (Catalog Number: MAB-0672, all were from Maixin Biotech Co., Ltd., Fuzhou, China). Immunohistochemistry was performed using EnVision. Positive and negative controls were used as appropriate. All results were diagnosed independently by two pathologists.</p>
</sec>
<sec id="s2_3">
<label>2.3</label>
<title>Pathological diagnosis and follow-up history</title>
<p>Postoperatively, tumor specimens were embedded in paraffin blocks and examined. A lobe of the lung, 14 cm&#xd7;11 cm&#xd7;3.5 cm in volume, was resected 4 cm away from the bronchial end close to the lung capsule, nodule 1, 3.5 cm&#xd7;2.2 cm&#xd7;2 cm in volume, was seen with a grayish, hard section surface and unclear boundary. Nodule 2, 2.8 cm&#xd7; 2.8 cm&#xd7;1.7 cm in volume, was seen 0.5 cm away from the bronchial end and 1.5 cm from the lung capsule, with gray-white, hard section surface and unclear boundary. Microscopically, the tumor cells in &#x201c;nodule 1&#x201d; mostly grew in cribriform and solid patchy forms with large and displaced nucleoli (<xref ref-type="fig" rid="f2">
<bold>Figure&#xa0;2</bold>
</xref>). Immunohistochemically, the tumor cells showed positive expression of CK7, TTF-1, napsin A, and Ki-67 (approximately 35% in hot spots), and were negative for CK5/6 and P40 (<xref ref-type="fig" rid="f3">
<bold>Figure&#xa0;3</bold>
</xref>). &#x201c;Nodule 1&#x201d; was revealed poor differentiation invasive adenocarcinoma. The proportions of tumor growth patterns in the complex glandular pattern, solid, and acinar without pleural invasion were 55%, 35%, and 10%, respectively. Histological examination of &#x201c;nodule 2&#x201d; revealed that the carcinomas formed irregular nests and strands of tumor cells separated by various amounts of fibrous stroma with cytoplasmic keratosis and no keratin pearls. Mitotic figures and necrosis were common (<xref ref-type="fig" rid="f2">
<bold>Figure&#xa0;2</bold>
</xref>). Immunohistochemically, the tumor cells were positive for CK5/6, P40, and Ki-67 (approximately 45% in hot spots) and negative for TTF-1 and napsin A (<xref ref-type="fig" rid="f3">
<bold>Figure&#xa0;3</bold>
</xref>). &#x201c;Nodule 2&#x201d; was a moderately differentiated SCC. Adenocarcinoma metastases were observed in the lymph nodes (8/15, 1/1, 0/2, 0/3, and 0/2 in groups 7, 10, 2, 4, and 11, respectively). Immunohistochemically, the metastatic tumor cells were positive for TTF-1 and negative for P40.</p>
<fig id="f2" position="float">
<label>Figure&#xa0;2</label>
<caption>
<p>Histological features associated with adenocarcinoma and squamous cell carcinoma in the same lobe of the lung. <bold>(A, B)</bold> Tumor cells in &#x201c;nodule 1&#x201d; mostly grow in complex glandular pattern, solid <bold>(A)</bold>), hematoxylin and eosin, &#xd7;100), with large nucleoli and displaced nucleoli <bold>(B)</bold>), hematoxylin and eosin, &#xd7;400). <bold>(C, D)</bold> Tumor cells form irregular nests and strands of tumor cells separated by various amounts of fibrous stroma <bold>(C)</bold>), hematoxylin and eosin, &#xd7;100) with cytoplasmic keratosis and no keratin pearl <bold>(D)</bold>), hematoxylin and eosin, &#xd7;400).</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fonc-15-1618619-g002.tif">
<alt-text content-type="machine-generated">Histological analysis showing four panels of tissue samples stained with hematoxylin and eosin. Panel A exhibits dense cellular regions with some clear spaces. Panel B highlights closely packed cells with prominent nuclei. Panel C shows swirling patterns of cells with varying density. Panel D features enlarged, irregularly shaped cells with distinct nuclear details.</alt-text>
</graphic>
</fig>
<fig id="f3" position="float">
<label>Figure&#xa0;3</label>
<caption>
<p>Immunohistochemistry of adenocarcinoma and squamous cell carcinoma in the same lobe of the lung. <bold>(A&#x2013;D)</bold> Immunohistochemically, the tumor cells show positive expression of CK7, TTF-1, napsin A, Ki-67 (approximately 35% in hot spots) in nodule 1 (&#xd7;100). <bold>(E&#x2013;G)</bold> Immunohistochemically, the tumor cells showed positive expression of CK5/6, P40, Ki-67 (approximately 45% in hot spots) in nodule 2 (&#xd7;100).</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fonc-15-1618619-g003.tif">
<alt-text content-type="machine-generated">Histological slides show various levels of staining and cellular distribution.   A: Dense brown staining indicating high expression.   B: Lighter, patchy staining.   C: Blue cellular details with minimal staining.   D: Moderate, uniform brown staining.   E: Strong, concentrated brown staining in glandular structures.   F: Brown staining with nuclei visible.   G: Scattered brown staining throughout.</alt-text>
</graphic>
</fig>
<p>The final diagnosis was lung adenocarcinoma combined with SCC and T2N2M0 according to the ninth edition of the tumor node metastasis (TNM) staging system and successfully discharged from the hospital after five days. Based on the patient&#x2019;s wishes, only immunohistochemistry was performed; sequencing and other related examinations were incomplete. The patient received systemic chemotherapy with paclitaxel and cisplatin postoperatively and recovered well. Follow-up at three months before the deadline for submission did not reveal any evidence of recurrence or other metastatic diseases.</p>
</sec>
</sec>
<sec id="s3" sec-type="discussion">
<label>3</label>
<title>Discussion</title>
<p>Based on the clinical information and immunohistochemical results, the pathological diagnoses were primary adenocarcinoma and SCC of the lower lobe of the right lung. This case study presents a complex and diagnostically challenging scenario. Such a combination is relatively uncommon compared with solitary lung malignancies and requires a comprehensive understanding.</p>
<p>MPLC are cases with &gt; 1 primary cancer occurring simultaneously or sequentially in the lungs (<xref ref-type="bibr" rid="B4">4</xref>). For sMPLC, tumors should be physically separated and histologically identical or different (<xref ref-type="bibr" rid="B15">15</xref>). The prevalence of low-dose CT lung cancer screening programs has boosted lung cancer diagnosis (<xref ref-type="bibr" rid="B16">16</xref>), and MPLC is becoming a common phenomenon in clinical practice (<xref ref-type="bibr" rid="B8">8</xref>, <xref ref-type="bibr" rid="B15">15</xref>). Since Martini first proposed the diagnostic criteria (<xref ref-type="bibr" rid="B9">9</xref>), MPLC has gained significant attention.</p>
<p>Most MPLC have the same histological type (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B5">5</xref>). Few reports have described the synchronous occurrence of adenocarcinoma and SCC in the same lobe. The first such case was reported by Kitamura et&#xa0;al., 1991 (<xref ref-type="bibr" rid="B12">12</xref>). Knowingly, including the present case, only six patients with primary synchronous occurrence of adenocarcinoma and SCC in the same lobe have been reported (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B12">12</xref>&#x2013;<xref ref-type="bibr" rid="B14">14</xref>). The clinicopathological features of the patients are summarized in <xref ref-type="table" rid="T1">
<bold>Table&#xa0;1</bold>
</xref>. Six male patients (age; 57&#x2013;77 years, mean age; 66.5 years). Most had a smoking history (four smokers, one former smoker, and one unknown). Only one of our patients had lymph node metastasis. All the patients underwent surgical resection. Three cases were located in the left lobe and three cases were located in the right lobe, and except for our case, the remaining five cases are all located in the upper lobe. The location of lung cancer in the upper or lower lobe may have some impact on prognosis, but it is not an independent decisive factor. Yngvar Nilssen et&#xa0;al. found that the right upper lobe comprised 31.2% of the tumors and 17.6% of the lung volume. The relative proportion of 1.77 was higher than in the other lobes (<xref ref-type="bibr" rid="B17">17</xref>). Hyun Woo Lee et&#xa0;al. found patients with lower lobe cancer showed a higher all-cause mortality rate than those with non-lower lobe cancer (<xref ref-type="bibr" rid="B18">18</xref>). Lymph node involvement in any primary tumor may upstage the overall disease and lead to a poor prognosis. Unfortunately, none of the other five cases had a complete follow-up history, and our patient was only followed up for three months before the deadline for submission, and we will continue to follow up.</p>
<table-wrap id="T1" position="float">
<label>Table&#xa0;1</label>
<caption>
<p>Summary of primary adenocarcinoma and squamous cell carcinoma in the same lung features.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="top" align="left">No.</th>
<th valign="top" align="left">Year</th>
<th valign="top" align="left">Sex</th>
<th valign="top" align="left">Age</th>
<th valign="top" align="left">Smoker</th>
<th valign="top" align="left">Size(cm)</th>
<th valign="top" align="left">Site</th>
<th valign="top" align="left">Pathological diagnosis</th>
<th valign="top" align="left">Metastasis</th>
<th valign="top" align="left">Therapy</th>
<th valign="top" align="left">Outcome</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">1 (<xref ref-type="bibr" rid="B12">12</xref>)</td>
<td valign="top" align="left">1991</td>
<td valign="top" align="left">M</td>
<td valign="top" align="left">70</td>
<td valign="top" align="left">Yes</td>
<td valign="top" align="left">&#x2460;1.7&#xd7;1.7<break/>&#x2461;1.8&#xd7;1.7</td>
<td valign="top" align="left">right upper lobe</td>
<td valign="top" align="left">&#x2460;Adec<break/>&#x2461;SCC</td>
<td valign="top" align="left">No</td>
<td valign="top" align="left">surgical resection</td>
<td valign="top" align="left">unknown</td>
</tr>
<tr>
<td valign="top" align="left">2 (<xref ref-type="bibr" rid="B13">13</xref>)</td>
<td valign="top" align="left">2017</td>
<td valign="top" align="left">M</td>
<td valign="top" align="left">58</td>
<td valign="top" align="left">Yes</td>
<td valign="top" align="left">&#x2460;3.7&#xd7;2.0<break/>&#x2461;4.5&#xd7;3.2</td>
<td valign="top" align="left">upper<break/>lobe of the left lung.</td>
<td valign="top" align="left">&#x2460;Adec<break/>&#x2461;SCC</td>
<td valign="top" align="left">No</td>
<td valign="top" align="left">Left upper lobectomy with lymph node dissection</td>
<td valign="top" align="left">unknown</td>
</tr>
<tr>
<td valign="top" align="left">3 (<xref ref-type="bibr" rid="B14">14</xref>)</td>
<td valign="top" align="left">2020</td>
<td valign="top" align="left">M</td>
<td valign="top" align="left">72</td>
<td valign="top" align="left">Yes</td>
<td valign="top" align="left">&#x2460;1.6<break/>&#x2461;1.6</td>
<td valign="top" align="left">right upper lobe and middle lobe</td>
<td valign="top" align="left">&#x2460;Adec<break/>&#x2461;SCC</td>
<td valign="top" align="left">No</td>
<td valign="top" align="left">surgical resection</td>
<td valign="top" align="left">unknown</td>
</tr>
<tr>
<td valign="top" align="left">4 (<xref ref-type="bibr" rid="B14">14</xref>)</td>
<td valign="top" align="left">2020</td>
<td valign="top" align="left">M</td>
<td valign="top" align="left">77</td>
<td valign="top" align="left">Former smoker</td>
<td valign="top" align="left">&#x2460;1.3<break/>&#x2461;1.6</td>
<td valign="top" align="left">left upper lobe</td>
<td valign="top" align="left">&#x2460;Adec<break/>&#x2461;SCC</td>
<td valign="top" align="left">No</td>
<td valign="top" align="left">surgical resection</td>
<td valign="top" align="left">unknown</td>
</tr>
<tr>
<td valign="top" align="left">5 (<xref ref-type="bibr" rid="B4">4</xref>)</td>
<td valign="top" align="left">2024</td>
<td valign="top" align="left">M</td>
<td valign="top" align="left">65</td>
<td valign="top" align="left">unknown</td>
<td valign="top" align="left">&#x2460;1.0<break/>&#x2461;3.9&#xd7;3.0</td>
<td valign="top" align="left">left upper lobe</td>
<td valign="top" align="left">&#x2460;Adec<break/>&#x2461;SCC</td>
<td valign="top" align="left">No</td>
<td valign="top" align="left">lobectomy of the left upper lung and mediastinal lymph nodes, adjuvant treatment</td>
<td valign="top" align="left">unknown</td>
</tr>
<tr>
<td valign="top" align="left">6 (present case)</td>
<td valign="top" align="left">2025</td>
<td valign="top" align="left">M</td>
<td valign="top" align="left">57</td>
<td valign="top" align="left">Yes</td>
<td valign="top" align="left">&#x2460;3.1&#xd7;2.6<break/>&#x2461;2.6&#xd7;2.3</td>
<td valign="top" align="left">lower lobe of the right lung</td>
<td valign="top" align="left">&#x2460;Adec<break/>&#x2461;SCC</td>
<td valign="top" align="left">Yes</td>
<td valign="top" align="left">resection of lower lobe of the right lung, dissection of mediastinal lymph nodes, and chemotherapy</td>
<td valign="top" align="left">Alive free of disease, 3mo</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn>
<p>M, male; mo, month; Adec, adenocarcinoma; SCC, squamous cell carcinoma.</p>
</fn>
</table-wrap-foot>
</table-wrap>
<p>The incidence of MPLC remains controversial because of varying diagnostic criteria and overlapping intrapulmonary metastases. Studies suggest that MPLC accounts for 0.2&#x2013;20% of lung cancer (<xref ref-type="bibr" rid="B1">1</xref>&#x2013;<xref ref-type="bibr" rid="B4">4</xref>), with an increasing trend attributed to improved diagnostic techniques and increased survival of patients with early stage lung cancer (<xref ref-type="bibr" rid="B8">8</xref>, <xref ref-type="bibr" rid="B15">15</xref>, <xref ref-type="bibr" rid="B16">16</xref>). The pathogenesis of MPLC involves complex interactions between genetic predispositions and environmental exposure. Smoking remains a major risk factor (<xref ref-type="bibr" rid="B19">19</xref>&#x2013;<xref ref-type="bibr" rid="B21">21</xref>). Chronic exposure to carcinogens creates a &#x201c;field&#x201d; of genetically damaged epithelial cells, increasing the risk of multiple independent primaries. This is supported by studies showing shared somatic mutations in adjacent normal lung tissue of smokers with MPLC (<xref ref-type="bibr" rid="B22">22</xref>). However, the genetic background of patients with MPLCs remains unclear (<xref ref-type="bibr" rid="B23">23</xref>). Molecular studies have indicated that MPLC tumors often exhibit distinct genetic profiles, such as epidermal growth factor receptor (EGFR), Kirsten rat sarcoma viral oncogene (KRAS), Erb-B2 Receptor Tyrosine Kinase 2 (ERBB2) tumor protein 53 (TP53), which support their independent clonal origin (<xref ref-type="bibr" rid="B24">24</xref>&#x2013;<xref ref-type="bibr" rid="B26">26</xref>). Genomic analyses have shown that multiple primary lesions are much more heterogeneous, unlike metastatic lesions (<xref ref-type="bibr" rid="B25">25</xref>). Chronic inflammation may promote clonal expansion of mutated cells and suppress antitumor immunity in MPLC (<xref ref-type="bibr" rid="B27">27</xref>). Unfortunately, because the patient refused to have genetic detection, there were no results of genetic detection in this case.</p>
<p>The management of MPLC requires a multidisciplinary approach that prioritizes curative intent for resectable lesions. Surgical resection remains the cornerstone of treatment (<xref ref-type="bibr" rid="B28">28</xref>, <xref ref-type="bibr" rid="B29">29</xref>). MPLC with EGFR, anaplastic lymphoma kinase, or ROS proto-oncogene 1, receptor tyrosine kinase alterations in individual lesions may benefit from lesion-specific targeted therapy (<xref ref-type="bibr" rid="B26">26</xref>). MPLC with high PD-L1 expression (xpres or mismatch repair deficiency may respond to immune checkpoint inhibitors (<xref ref-type="bibr" rid="B27">27</xref>).</p>
<p>A key challenge is differentiating MPLC from metastases to avoid overtreatment (<xref ref-type="bibr" rid="B30">30</xref>). The clinical diagnosis of MPLC is predominantly based on the Martini-Melamed diagnostic criteria, which primarily rely on tumor location, histologic features, presence or absence of carcinoma <italic>in situ</italic>, and other characteristics (<xref ref-type="bibr" rid="B9">9</xref>). The American College of Chest Physicians (ACCP) and the International Association for the Study of Lung Cancer (IASLC) proposed updated diagnostic criteria (<xref ref-type="bibr" rid="B10">10</xref>). The 2016 IASLC criterion provided a more detailed description of MPLC diagnostic criteria, incorporating the Comprehensive Histologic Assessment (CHA) process (<xref ref-type="bibr" rid="B11">11</xref>). Accurate diagnosis of MPLC is based on histologic type and onset interval and does not incorporate genetic analysis (<xref ref-type="bibr" rid="B15">15</xref>, <xref ref-type="bibr" rid="B23">23</xref>). Microscopic morphology and immunohistochemistry are helpful for differential diagnosis. SCC usually exhibits pronounced keratinization and intercellular bridges and is diffusely positive for P63 and P40; adenocarcinoma is positive for TTF-1, napsin-A and neuroendocrine tumors are positive for CD56, synaptophysin, and chromogranin (<xref ref-type="bibr" rid="B31">31</xref>, <xref ref-type="bibr" rid="B32">32</xref>).</p>
<p>Studies have indicated that patients with early stage MPLC have better survival outcomes than those with metastatic disease (<xref ref-type="bibr" rid="B15">15</xref>, <xref ref-type="bibr" rid="B28">28</xref>). Poor prognostic factors include advanced tumor stage and lymph node involvement (<xref ref-type="bibr" rid="B33">33</xref>, <xref ref-type="bibr" rid="B34">34</xref>). Chest CT may predict unexpected recurrence and metastasis after radical surgery for MPLC (<xref ref-type="bibr" rid="B35">35</xref>). In the future single-cell RNA sequencing may identify distinct immune cell profiles in MPLC (<xref ref-type="bibr" rid="B36">36</xref>). Liquid biopsy for clonality assessment may distinguish MPLC from metastasis (<xref ref-type="bibr" rid="B37">37</xref>).</p>
<p>Overall, we report a rare case of primary synchronous adenocarcinoma and SCC in the same lobe of the lung with adenocarcinoma metastasis to the lymph nodes. Complete surgical resection was the treatment of choice. Careful assessment of the histological features and immunohistochemistry enables an efficient diagnosis.</p>
</sec>
</body>
<back>
<sec id="s4" sec-type="data-availability">
<title>Data availability statement</title>
<p>The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.</p>
</sec>
<sec id="s5" sec-type="ethics-statement">
<title>Ethics statement</title>
<p>The studies involving humans were approved by Weifang People&#x2019;s Hospital (First Affiliated Hospital of Shandong Second Medical University) Institutional Review Board for Human Studies. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent for participation in this study was provided by the participants&#x2019; legal guardians/next of kin. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.</p>
</sec>
<sec id="s6" sec-type="author-contributions">
<title>Author contributions</title>
<p>C-SL: Data curation, Conceptualization, Writing &#x2013; original draft, Writing &#x2013; review &amp; editing. Y-XZ: Data curation, Writing &#x2013; original draft, Writing &#x2013; review &amp; editing, Conceptualization. C-YW: Methodology, Data curation, Conceptualization, Writing &#x2013; original draft. G-DX: Data curation, Methodology, Writing &#x2013; original draft, Conceptualization. M-QY: Data curation, Conceptualization, Writing &#x2013; original draft, Writing &#x2013; review &amp; editing.</p>
</sec>
<sec id="s7" sec-type="funding-information">
<title>Funding</title>
<p>The author(s) declare that no financial support was received for the research and/or publication of this article.</p>
</sec>
<sec id="s8" sec-type="COI-statement">
<title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="s9" sec-type="ai-statement">
<title>Generative AI statement</title>
<p>The author(s) declare that no Generative AI was used in the creation of this manuscript.</p>
</sec>
<sec id="s10" sec-type="disclaimer">
<title>Publisher&#x2019;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
<fn-group>
<title>Abbreviations</title>
<fn fn-type="abbr" id="abbrev1">
<p>sMPLC, Synchronous multiple primary lung cancer; SCC, squamous cell carcinoma; ACCP, American College of Chest Physicians; IASLC, International Association for the Study of Lung Cancer; CT, computed tomography; SCCA, Squamous Cell Carcinoma Antigen; CEA, Carcinoembryonic antigen; NSE, Neuron-Specific Enolase; NSCLC, non-small cell lung cancer; HE, hematoxylin-eosin; CK, cytokeratin; TTF-1, thyroid transcription factor-1; TNM, tumor node metastasis; EGFR, epidermal growth factor receptor; KRAS, Kirsten rat sarcoma viral oncogene; ERBB2, Erb-B2 Receptor Tyrosine Kinase 2; TP53, tumor protein 53; PD-L1, programmed cell death ligand 1.</p>
</fn>
</fn-group>
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