Papillary thyroid cancer (PTC) is the most prevalent type of thyroid malignancy, accounting for approximately 80% of all thyroid cancer cases (1). Although generally associated with a favorable prognosis, PTC can exhibit varying degrees of aggressiveness, with certain cases demonstrating increased potential for invasion and metastasis (2). Angioinvasion, the invasion of cancer cells into blood or lymphatic vessels, is a critical determinant of tumor behavior and can significantly impact patient outcomes. Accurate assessment of angioinvasion in PTC is crucial for predicting disease progression, selecting appropriate treatment strategies, and optimizing patient management. While traditional histopathological techniques, such as lymphovascular invasion evaluation, have been utilized to assess angioinvasion, the identification of specific molecular markers has the potential to enhance diagnostic precision and prognostic accuracy (3).

Nowadays, various molecular markers have been investigated for their potential association with angioinvasion in PTC. Notably, vascular endothelial growth factor (VEGF), a well-known pro-angiogenic factor, has shown correlations with angioinvasion and tumor aggressiveness (4). Additionally, CD34, a cell surface glycoprotein used as a marker of microvessel density, and podoplanin, a protein involved in lymphatic vessel formation, have been implicated in angioinvasion in PTC (5, 6). Among others, oxidative stress markers, sortilin and integrins have been implicated in angiogenesis and may contribute to the angioinvasive phenotype of PTC (2). Understanding the molecular mechanisms underlying angioinvasion in PTC is crucial for improving diagnostic accuracy, prognostication, and therapeutic decision-making (7).

Through a comprehensive review of the existing literature, this study aims to consolidate the current knowledge on angioinvasion markers in PTC and explore promising novel markers. The study aimed to identify potential markers that can reliably indicate the presence of angioinvasion in PTC, which can improve risk stratification and facilitate personalized therapeutic interventions for patients with PTC.

This literature review employed a systematic approach to identify and analyze studies investigating novel angioinvasion markers in PTC. The methodology ensured the inclusion of relevant studies and provided a rigorous evaluation of the available literature in this field (8). Thus, a systematic search was performed to identify relevant articles from various electronic databases, including PubMed, Scopus, and Web of Science (9). The search strategy utilized a combination of keywords and controlled vocabulary terms related to PTC, angioinvasion, and molecular markers. The search was conducted with no restrictions on language or publication date. Articles were included if they met the following criteria: PTC, investigated angioinvasion markers, provided relevant data or findings, and were published in peer-reviewed journals. Studies that were reviews, editorials, or conference abstracts were excluded. Full-text articles of the selected studies were then assessed for eligibility. Data from the included articles were extracted using a standardized form. The extracted data included study characteristics (e.g., author, year of publication), patient population, study design, angioinvasion markers investigated, methodology, and key findings. The extracted data were analyzed thematically to identify common trends, associations, and novel markers implicated in angioinvasion in PTC. The findings were summarized and presented descriptively. The quality and risk of bias of the included studies were evaluated using appropriate tools, such as the Newcastle-Ottawa Scale for observational studies (10) or the Cochrane Collaboration’s tool for randomized controlled trials (11). As this study is a literature review, ethical approval was not required. The data were obtained from published studies, ensuring confidentiality and anonymity of the participants. The limitations of this study included the potential for publication bias, as only peer-reviewed articles were included, and the reliance on available literature. Additionally, the heterogeneity of the included studies may have affected the ability to perform quantitative analysis.

PTC is the most common type of thyroid cancer, accounting for approximately 80-90% of all thyroid malignancies (12). The incidence of PTC has been steadily increasing over the past few decades in many countries worldwide (13, 14). This rise in incidence is partly attributed to increased detection due to advanced imaging techniques and improved diagnostic practices. Furthermore, PTC exhibits a strong female predominance. Women are approximately three times more likely to develop PTC than men (15). This gender disparity has been observed consistently across different populations and geographic regions. Several studies have investigated potential hormonal (estrogen receptors have been found in thyroid tissue, and estrogen can stimulate the growth and proliferation of thyroid cells) and genetic factors (such as BRAF mutation, other genetic alterations, such as RET/PTC rearrangements and RAS mutations) contributing to this gender difference (16). Moreover, PTC can affect individuals of all age groups, but it is most commonly diagnosed in adults aged 30-50 years. Thus, the incidence of PTC has been increasing among younger populations, particularly adolescents and young adults. The reasons for this age-specific trend are not fully understood, and further research is needed to explore potential risk factors (15). Nevertheless, PTC incidence rates vary significantly across different countries and regions. Higher incidence rates have been reported in regions with a higher iodine intake, such as areas of high goiter prevalence (17). The impact of environmental factors, genetic predisposition, and variations in healthcare practices on these geographical differences is a subject of ongoing research (17). Interestingly, exposure to ionizing radiation, especially during childhood, is a well-established risk factor for PTC (18). Individuals who have undergone radiation therapy for medical conditions, such as Hodgkin’s lymphoma or head and neck cancers, have an increased risk of developing PTC (19). Studies have consistently shown a dose-response relationship between radiation exposure and PTC risk.

The study conducted by Baloch et al. aimed to identify prognostic factors in well-differentiated follicular-derived carcinoma. It investigated various clinicopathological factors to determine their impact on patient prognosis. The results of the study revealed several significant prognostic factors associated with PTC prognosis, including age, tumor size, presence of lymph node metastasis, extrathyroidal extension, and distant metastasis. Older age, larger tumor size, presence of lymph node metastasis, and extrathyroidal extension were correlated with a poorer prognosis, while the presence of distant metastasis indicated a significantly worse outcome. The study provided valuable insights into prognostic factors, such as angioinvasion measurement, that can help predict the outcomes of patients with well-differentiated follicular-derived carcinoma, specifically PTC. These findings emphasize the importance of clinicians making informed decisions regarding treatment strategies and patient management based on angioinvasion detection and the presence of lymph node metastasis. Ultimately, angioinvasion detection could lead to improved patient care and outcomes (20).

The clinical management of PTC involves a multidisciplinary approach that includes surgery, radioactive iodine (RAI) therapy, thyroid hormone replacement, and long-term follow-up (21). The specific management strategy may vary depending on factors such as tumor characteristics, stage, patient age, and angioinvasion with lymph metastasis detection (22). The primary treatment for PTC is most frequently thyroidectomy. The extent of surgery may vary from a total thyroidectomy to a lobectomy (23). Lymph node dissection may be performed if there is evidence of lymph node involvement. The goal of surgery is to remove the primary tumor and any involved lymph nodes while minimizing the risk of recurrence. Following thyroidectomy, RAI therapy may be recommended for certain PTC patients, particularly those with high-risk features such as larger tumors, angioinvasion presents, lymph node involvement, or distant metastasis (24). RAI therapy involves the administration of a radioactive iodine isotope (iodine-131) that selectively targets and destroys any remaining thyroid tissue or cancer cells. This adjuvant therapy aims to eliminate residual disease and reduce the risk of recurrence (25). After thyroidectomy, lifelong thyroid hormone replacement therapy is essential to achieve suppression of thyroid-stimulating hormone (TSH) levels and to maintain normal thyroid hormone levels. This involves daily oral intake of synthetic thyroid hormone (levothyroxine) to replace the natural thyroid hormone produced by the thyroid gland (26). The goal is to suppress TSH levels, which helps prevent tumor growth and recurrence. Regular monitoring of thyroid hormone levels and adjustment of medication dosage is necessary to ensure optimal hormone replacement (27). Thus, PTC patients require long-term follow-up care to monitor for disease recurrence, assess treatment response, and manage any potential complications (28). In cases of locally advanced or metastatic PTC that does not respond to standard treatments, additional therapeutic options may be considered (29). These may include targeted therapies, such as tyrosine kinase inhibitors (e.g., lenvatinib, sorafenib), which block specific molecular pathways involved in cancer growth and angiogenesis. Clinical trials investigating novel therapies may also be an option for eligible patients (30, 31). From the other hand, in low-risk PTC less invasive techniques could be use. Thermal ablation refers to the use of heat-based techniques to treat thyroid nodules, including PTC. It is a minimally invasive procedure that aims to destroy or shrink the tumor without the need for surgery (32). Thermal ablation has shown promising results in the treatment of PTC, with studies demonstrating effective tumor control and minimal complications (33). However, it is important to note that surgery, such as thyroidectomy and lobectomy, remains the primary treatment approach for most cases of PTC (34). Therefore, identifying the presence or absence of angioinvasion would allow avoiding invasive procedures and the need for therapy for a large group of patients, as well as the requirement for lifelong observation. Furthermore, it would help identify a subgroup of patients at high risk for more aggressive progression of PTC, where the introduction of more radical therapy would be recommended as soon as possible.

The evaluation of angioinvasion markers in PTC typically involves the assessment of specific molecular and cellular markers associated with tumor angiogenesis and invasiveness. These markers may include Vascular Endothelial Growth Factor (VEGF), CD34, podoplanin, integrins, and matrix metalloproteinases (MMPs) and oxidative stress markers. Through various techniques such as immunohistochemistry, gene expression analysis, and biomolecular assays, the expression levels and presence of these markers can be quantified and correlated with angioinvasion in PTC (3).

Accurate evaluation of angioinvasion markers holds significant clinical implications. It can provide valuable information regarding tumor behavior, likelihood of lymph node metastasis, risk of recurrence, and overall patient prognosis (35). This information can guide treatment decisions, such as the extent of surgery (total thyroidectomy vs. lobectomy), the need for lymph node dissection, and the consideration of adjuvant therapies. Furthermore, the identification and validation of novel angioinvasion markers in PTC have the potential to revolutionize clinical treatment options. Targeted therapies that specifically inhibit angiogenesis and tumor invasiveness could be developed, leading to improved patient outcomes (36). These therapies may include anti-angiogenic agents, tyrosine kinase inhibitors, or other molecular targeted therapies aimed at disrupting the signaling pathways involved in angiogenesis and tumor progression (37). However, it is important to note that while several markers have shown promise in preclinical and early clinical studies, further research is needed to validate their clinical utility, establish standardized diagnostic criteria, and assess their effectiveness in larger patient populations (38). Rigorous clinical trials and translational research efforts are required to determine the efficacy, safety, and long-term outcomes of targeting angioinvasion markers in PTC treatment. Nevertheless, the evaluation of angioinvasion markers among PTC patients is essential for accurate prognosis determination and treatment decision-making (39). Continued research into novel markers and the development of targeted therapies hold great potential for improving clinical outcomes and personalized treatment options for PTC patients (40).

Oxidative stress is known to play a role in the angioinvasion of PTC. Oxidative stress refers to an imbalance between the production of reactive oxygen species (ROS) and the body’s antioxidant defense mechanisms, leading to cellular damage (41). Several studies have indicated that oxidative stress is involved in promoting angiogenesis, which is the process of new blood vessel formation that facilitates tumor growth and metastasis (42). In PTC, oxidative stress can arise from various sources, including increased ROS production by tumor cells, inflammation, and altered antioxidant capacity (43). The excessive production of ROS can induce the activation of signaling pathways that promote angiogenesis. These pathways involve factors such as VEGF, hypoxia-inducible factor 1-alpha (HIF-1α), and nuclear factor-kappa B (NF-κB), which contribute to the formation of new blood vessels in the tumor microenvironment (44). Furthermore, oxidative stress can lead to DNA damage and genetic alterations in tumor cells, promoting their invasive properties. It can also influence the expression of matrix metalloproteinases (MMPs), enzymes involved in extracellular matrix degradation and tumor invasion (45). MMPs play a crucial role in facilitating the breakdown of basement membranes and blood vessel walls, allowing tumor cells to invade surrounding tissues and enter the bloodstream (46).

The study performed by Azouzi et al. concerned on the role of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) as a critical mediator of BRAFV600E-induced downregulation of the sodium/iodide symporter (NIS) in PTC aimed to understand the mechanism underlying the loss of NIS expression in this disease. The results of the study demonstrated that activation of the BRAFV600E pathway led to upregulation of NOX4 expression, which in turn resulted in the overproduction of ROS in thyroid cancer cells. The increased ROS levels induced oxidative stress, leading to a decrease in NIS expression. It was found that NOX4 is directly involved in this process, and its inhibition restored NIS expression in thyroid cancer cells. Furthermore, it was observed that in tissue samples obtained from patients with papillary thyroid carcinoma, the presence of BRAFV600E and NOX4 correlated with decreased NIS expression. These findings highlight the significant role of NOX4 as a mediator of NIS downregulation in BRAFV600E-mutated thyroid cancer. These discoveries have important clinical implications as the loss of NIS expression hinders the effective use of radioactive iodine therapy. Understanding the mechanism regulating NIS loss may contribute to the development of new therapies aimed at restoring NIS function and enhancing the effectiveness of treatment for iodine-refractory thyroid cancer (47). The following study performed by Weyemi et al. concerned on the intracellular expression of the enzyme NOX4, a generator of ROS, in normal and cancer thyroid tissues aimed to investigate the role of NOX4 in the pathogenesis of thyroid cancer. The results of the study showed that NOX4 was expressed in both normal and cancerous thyroid tissues. However, the expression level of NOX4 was significantly higher in cancerous tissues compared to healthy tissue. It was also observed that NOX4 expression correlated with the presence of the transcription factor HIF-1α (hypoxia-inducible factor 1α) in thyroid cancer cells. HIF-1α is a known regulator of metabolic processes and the response to hypoxia. Additionally, it was observed that a high level of NOX4 expression was associated with more advanced clinical stages of thyroid tumors. This suggests a potential role of NOX4 in the progression and aggressiveness of thyroid cancer. These findings suggest that NOX4 may play a significant role in redox processes and the pathogenesis of thyroid cancer. Increased NOX4 expression in cancerous tissues may lead to the overproduction of ROS, which in turn can influence cell proliferation, angiogenesis, and other processes related to tumor development. Despite promising results, further research is needed to better understand the mechanisms regulating NOX4 expression and its role in the pathogenesis of thyroid cancer. This may lead to the identification of NOX4 as a potential therapeutic target or prognostic biomarker in this disease (48). Another study conducted by Mseddi et al. evaluating the nuclear 8-hydroxyguanosine (8-OHdG) expression in autoimmune thyroid diseases and PTC, and its relationship with cancer-related proteins p53, Bcl-2, and Ki-67 aimed to investigate potential differences in the level of oxidative DNA damage between these two disease states. The results of the study showed that nuclear 8-OHdG expression was increased in both autoimmune thyroid diseases and PTC compared to healthy thyroid tissue. However, significant differences in the expression level were observed between these two patient groups. In the case of PTC, a higher level of 8-OHdG expression was observed compared to autoimmune thyroid diseases. Additionally, a significant correlation was found between 8-OHdG expression and the cancer-related proteins p53, Bcl-2, and Ki-67 in the group of PTC patients. Higher levels of 8-OHdG expression were associated with higher levels of p53 and Ki-67, which are markers of cell proliferation, and lower levels of Bcl-2 protein, which is associated with apoptosis. The conclusions from this study suggest that oxidative DNA damage, represented by 8-OHdG expression, is present in both autoimmune thyroid diseases and PTC. However, differences in expression levels and associations with cancer-related proteins indicate potentially different mechanisms of oxidative stress in these two disease states. Further research is needed to better understand the role of oxidative DNA damage in autoimmune thyroid diseases and PTC, as well as the potential use of 8-OHdG as a diagnostic or prognostic biomarker in these diseases (49).

Understanding the involvement of oxidative stress in PTC angioinvasion is essential for developing targeted therapies (35). Strategies aimed at reducing oxidative stress or inhibiting specific molecular pathways associated with angiogenesis and invasion may hold promise for inhibiting tumor progression and improving patient outcomes (25). However, further research is needed to fully elucidate the mechanisms by which oxidative stress contributes to PTC angioinvasion and to identify potential therapeutic targets.

The evaluation of angioinvasion markers among papillary thyroid cancer (PTC) patients plays a crucial role in determining prognosis and guiding treatment decisions. When many studies have investigated the role of oxidative stress and VEGF in association with PTC angiogenesis, several factors have never been validated in clinical management. Thus, to confirm the role of VEGF as a marker of angiogenesis in PTC and to evaluate the clinical significance of new markers, such as MMP-2, Sortilin and CD34 further research and validation studies on larger patient populations are necessary. Studies on these factors can provide a more comprehensive understanding of angiogenesis in PTC and enable the identification of patients who may require more aggressive clinical management. The investigation of angiogenesis markers in PTC has also enabled the identification of medical targets in more advanced types of PTC, which form the basis for new clinical studies on PTC treatment.

AB: conceptualization, data curation, investigation, software, validation, visualization, writing – original draft. MK: formal analysis, investigation, writing – original draft. AK: methodology, supervision, validation, writing – review & editing. AP-K: conceptualization, funding acquisition, resources, validation, visualization, writing – review & editing.