Pituitary adenomas (PAs) are among the most prevalent benign intracranial tumors, originating from the adenohypophyseal cells of the anterior pituitary gland. They constitute approximately 10- 15% of all surgically resected intracranial tumors, making them a significant clinical entity within neuro-oncology and endocrinology (1, 2). Epidemiological studies indicate that PAs are common in the general population, with prevalence rates reaching up to 20% based on autopsy and radiological findings (3). The tumors present a broad spectrum of clinical manifestations, primarily determined by their size and hormonal activity. Microadenomas are defined as tumors smaller than 1cm, often identified incidentally or during evaluation for endocrine dysfunction, while macroadenomas exceed 1 cm and are more likely to cause compressive symptoms such as headaches, visual disturbances, and hypopituitarism. Moreover, PAs are classified based on their hormonal secretion into functioning and non-functioning adenomas. Functioning adenomas secrete excess hormones like prolactin, growth hormone (GH), adrenocorticotropic hormone (ACTH), and others, leading to clinical syndromes such as hyperprolactinemia, acromegaly, and Cushing’s disease. Conversely, non-functioning adenomas may remain asymptomatic until they grow sufficiently large to induce compressive effects (3–5). Despite their benign histology, PAs display a capacity for invasive growth, with approximately 45-55% invading local structures such as the cavernous sinus, sphenoid sinus, or dura mater. This local invasion complicates surgical resection and increases the likelihood of residual disease and recurrence. Residual disease and recurrence are clinically significant, as they often necessitate repeated surgical interventions, long-term medical management, and radiotherapy, thereby increasing patient morbidity, diminishing quality of life, and raising healthcare costs. Accurate assessment of invasiveness and tumor behavior remains challenging, as traditional histopathological markers, like Ki-67 proliferation index and p53 expression, lack sufficient predictive power. Hence, there is a pressing need to identify reliable biomarkers that can facilitate early diagnosis, predict tumor aggressiveness, and guide personalized treatment strategies (6).

Recent advances in molecular biology have revolutionized our understanding of tumorigenesis, emphasizing the pivotal roles of genetic and epigenetic factors beyond classical oncogenes and tumor suppressor genes. Notably, non-coding RNAs (ncRNAs), including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), have emerged as critical regulators of gene expression. These molecules, although not translating into proteins, influence cellular processes such as proliferation, apoptosis, differentiation, and metastasis. In particular, lncRNAs, which are transcripts longer than 200 nucleotides, have been implicated in tumor initiation and progression across various cancer types, including neuroendocrine tumors such as pituitary adenoma, papillary thyroid carcinoma and gastrointestinal neuroendocrine tumors (7–9).

Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) lncRNA, which was initially identified as an oncogene in a study of non-small cell lung cancer (NSCLC), is situated at 11q13 (9). Since its discovery, MALAT1 has contributed significantly to the progression, metastasis, drug resistance, and treatment of cancer, as well as its clinical importance in predicting the tumor metastasis of early-stage cancer, particularly lung cancer (9, 10). Subsequently, overexpression of MALAT1 was also found to be involved in tumor cell proliferation, migration, invasion, and apoptosis in various cancers. In addition, increased expression level of MALAT1 can also be used as a potential biomarker for tumor diagnosis and prognosis, including liver, colorectal, pancreatic, papillary thyroid, renal cancers, and gastrointestinal diffuse large B-cell lymphoma (11–16).

In addition to MALAT1, other molecular markers such as Ki-67, p53 are being explored to improve diagnostic accuracy and prognostic predictions. Ki-67, a nuclear protein associated with cellular proliferation, has been correlated with tumor aggressiveness, although its standalone utility remains limited. Mutations and expression patterns of p53, a tumor suppressor, are also under investigation, yet their roles in PA are not fully clarified. Given the complex molecular landscape of PAs, integrating genetic, epigenetic, and molecular profiles could enhance our ability to stratify tumors based on their invasive potential and risk of recurrence. Specifically, the study of lncRNA gene variants, such as those in MALAT1, may unearth novel insights into tumor biology and facilitate the development of targeted therapies in patients with PA.

A case-control study was conducted involving 390 subjects divided into two groups: the control group (n = 245) and a group of PA (n = 145). After forming the groups of subjects, MALAT1 rs1194338, rs619586, and rs3200401 variants were analyzed. The median age of PA patients was 53 years. The patients’ group was later divided into subgroups by the PA’s tumor size, hormonal activity, invasiveness, and recurrence. The median age of the control group was 55 years. The age and gender did not differ between study groups (p > 0.05). The demographic data of the subjects are presented in Table 1.

We examined the genotype and allele frequency distributions of MALAT1 rs1194338, rs619586, and rs3200401 in the PA and the control groups. The analysis showed that the MALAT1 rs619586 G allele is statistically significantly more frequent in PA patients than in the control group subjects (4.1% vs. 0.8%, p = 0.001) (Table 2).

To assess the impact of MALAT1 gene variants on the onset of PA, we conducted a binary logistic regression analysis (Table 3). The statistically significant findings revealed that the G allele of MALAT1 rs619586 increases the odds of developing PA by 4.1-fold under the additive model (OR= 4.139, 95% CI: 1.365-12.551, p = 0.012).

This study aimed to investigate the involvement of lncRNA MALAT1 gene variants in the pathology of pituitary adenoma and their potential clinical relevance.

Long non-coding RNAs (lncRNAs) have emerged as important regulators of gene expression, chromatin structure, and cellular homeostasis. In pituitary adenomas, lncRNAs modulate fundamental biological processes such as cell proliferation, apoptosis, differentiation and tumour progression, thereby influencing tumour phenotype and aggressiveness (26, 27).

Also known as nuclear enrichment autosomal transcript 2 (NEAT2), MALAT1 was initially identified through subtractive hybridization as one of the transcripts most significantly overexpressed in metastatic non-small cell lung cancer tissues (26). Since then, MALAT1 has become one of the most extensively studied lncRNAs, with accumulating evidence suggesting its multifaceted roles in pituitary adenoma biology (28). The available literature supports the concept that MALAT1 may contribute to tumorogenesis and progression in pituitary adenomas through mechanisms similar to those described in other cancers, such as promoting proliferation, angiogenesis, apoptosis, and epithelial-mesenchymal transition (EMT) (26, 29, 30).

In recent years, studies investigating the role of lncRNA MALAT1 in the pathogenesis of pituitary adenoma development have shown inconsistent results. Li and colleagues evaluated MALAT1 alongside MEG3 and HOTAIR expression in non-functioning pituitary adenoma (NFPAs) and reported no significant difference in MALAT1 expression between tumor and normal pituitary tissue, nor did they correlate with clinicopathological parameters (31). It seems that MALAT1 may exert an anti-cancer effect in NFPAs (32). Lu et al. examined growth-hormone-secreting pituitary adenomas (GHPA) and reported that high H19 expression was associated with tumour invasion, whereas MALAT1 expression did not differ significantly between invasive and non-invasive GHPA (33). Recent work by Ghafouri-Fard et al. analysed lncRNAs in pituitary adenoma tissues and observed a strong positive correlation between PVT1 and MALAT1, suggesting that interactions between lncRNAs may contribute to tumour pathogenesis and highlight the complex regulatory networks in which MALAT1 participates (34).

While several MALAT1 SNVs, including rs619586, have been investigated in lung, colorectal, hepatocellular and other cancers, the evidence that these variants influence risk or progression, often through changes in MALAT1 expression and downstream oncogenic pathways, is inconsistent (35). To date, there is currently no established evidence of direct or consistent association between MALAT1 SNVs and neuroendocrine tumors, particularly PAs, susceptibility or behavior (29, 36).

Our study is the first to demonstrate that the MALAT1 rs6198586 G allele is significantly more frequent in pituitary adenoma patients compared to controls and is associated with tumour aggressiveness, including invasiveness and recurrence. These results contrast with most other reports in other diseases, where the rs619586 allele tends to be protective. It is important to note that rs619586 is located within a non-coding region of the MALAT1 gene, and direct functional evidence demonstrating its impact on MALAT1 expression, splicing, or RNA-binding properties in pituitary cells is currently lacking (28).

Although functional studies in other tumor types have linked rs619586 to altered MALAT1 expression and tumor-related phenotypes, these effects appear to be tissue-specific (18, 21). Therefore, the present findings should be interpreted as evidence of genetic association rather than direct mechanistic causality. Functional studies in pituitary-derived models will be required to elucidate the molecular mechanisms underlying the observed associations.

For example, a meta-analysis of nine case-control studies involving several cancer types found that the rs619586 G allele was associated with reduced overall cancer risk in Asians (odds ratio ≈ 0.87 for the G vs. A allele) (37), and a case-control study of papillary thyroid cancer (PTC) demonstrated that the rs619586 G allele was a protective factor (OR ≈ 0.76) while decreasing.

MALAT1 expression, suppressed cell proliferation and increased apoptosis (18). Similarly, in studies of cerebral tumors, for example meningioma, the rs619586 A>G variant lowers MALAT1 expression and reduces tumor invasiveness (19). In contrast, in oral squamous cell carcinoma (OSCC), the rs619586 AG/GG genotype was associated with higher tumour stage and larger tumours, especially in patients with a betel-nut chewing habit (21). Together, these findings illustrate the tissue-specific nature of rs619586, it is protective or neutral in most cancers, yet linked to aggressiveness in OSCC and, as our data show, in pituitary adenoma.

The current literature suggests that rs3200401 and rs1194338 have cancer type-specific effects, in some cases, and in others are associated with aggressive disease. In advanced lung adenocarcinoma patients, the rs3200401 T allele was associated with better survival (38). Qu Y et al. reported that the T allele increases the risk of esophageal squamous cell carcinoma (39). A Taiwanese prostate cancer cohort showed that male patients with at least one rs1194338 A allele had more than a threefold increased risk of lymph-node metastasis (40). In our study, we did not observe any significant associations between these MALAT1 variants and pituitary adenoma characteristics.

A high Ki-67 LI is generally interpreted as evidence of rapid proliferation and potential invasiveness into surrounding structures (41). Several Ki-67 cut-off values have been proposed to stratify aggressiveness in pituitary adenomas, ranging from 1,5% to 4% (42). Some studies have linked higher Ki−67 indices to invasiveness or recurrence, whereas others have not.

A large retrospective analysis of pituitary adenomas found no significant differences in Ki-67 LI with respect to sex, tumor type, diameter, or invasiveness, although the same study reported an association between higher Ki-67 LI and recurrence (43). In a review involving 28 studies on Ki- 67, 18 studies reported high Ki-67 expression in recurrent adenomas, while the other 10 studies showed no correlation (44). A subsequent meta−analysis concluded that a Ki−67 ≥ 3% warrants closer postoperative surveillance, as these tumors were more likely to recur; however, Ki-67 is not an independent predictor of tumor recurrence. Moreover, factors such as tumor subtype, extent of surgical resection, cavernous sinus invasion and hormonal activity often exert a stronger influence on recurrence than Ki−67 alone (45).

Our findings that Ki-67 LI did not correlate with tumor size, invasiveness, hormonal activity or recurrence align with those studies showing limited prognostic utility of Ki-67. Also there were no significant results between Ki-67 Li and MALAT1 genetic variations.

Normal pituitary tissue expresses little p53, and most pituitary adenomas show only minimal or focal p53 staining. Earlier studies have suggested that tumors with high p53 expression exhibit more frequent tumor progression and cavernous sinus invasion, but they did not assess recurrence (46, 47). Oliveira et al. subsequently reported no correlation between p53 expression and PA recurrence. In their study of 148 pituitary adenomas, only 1.3% were p53-positive, indicating that p53 is insufficient as a routine marker of recurrence (48). Our study demonstrated that macroadenomas had significantly higher p53 H-scores than microadenomas, however, p53 expression was not associated with invasiveness, hormonal activity or recurrence. Also, we found that patients carrying the MALAT1 rs619586 AA genotype had higher p53 H-scores than those with AG genotype (median 26.33 vs. 9.67, p = 0,001). Moreover, p53-positive adenomas generally display a higher Ki-67 compared with p53-negative tumors, which is consistent with previous observations (47). Although p53 H-scores were higher in tumors from patients with the rs619586 AA genotype, this does not contradict the association of the rs619586 G allele with more aggressive clinical features. In pituitary adenomas, increased p53 immunoreactivity often reflects accumulation of dysfunctional or stabilized p53 protein and does not consistently correlate with invasion, recurrence, or proliferative activity (47). Therefore, p53 expression should be interpreted as a context-dependent cellular response rather than a direct indicator of tumor aggressiveness (46, 49). The discordant directions observed between p53 expression and clinical aggressiveness further support the notion that rs619586-associated tumor behavior is unlikely to be mediated directly through p53 signaling.

Despite the valuable insights gained through this exploratory study, limitations undoubtedly exist. Future studies could evaluate these variants in larger PA cohorts, in diverse ethnic groups and functional assays to determine whether they influence tumour susceptibility or behaviour, and functional assays should clarify how these variants modulate MALAT1 expression or its interactions with downstream targets.

Although rs619586 was consistently associated with PA risk and several aggressive clinical features in the present cohort, independent replication in an external population has not yet been performed. Therefore, rs619586 should be regarded as a potential or candidate genetic marker rather than a validated biomarker. Replication in independent, geographically distinct cohorts will be required to confirm these findings and to determine their generalizability.

Although age and sex were matched between cases and controls, multivariable logistic regression models incorporating clinical factors such as hormone excess, medication use, and treatment history were not applied in the present analysis. This study was designed primarily to evaluate genetic associations, and many clinical variables are intrinsically related to tumor phenotype and post-diagnostic management rather than baseline genetic risk. In addition, the low frequency of certain variants limited the feasibility of stable multivariable modeling.

Given the low number of rs619586 G-allele carriers, odds ratio estimates derived from standard logistic regression, particularly in subgroup analyses, may be affected by sparse data bias and should therefore be interpreted with caution. Future studies in larger cohorts will be required to obtain more stable effect estimates and to delineate the independent and combined effects of genetic and clinical factors on pituitary adenoma risk and behavior.

In addition, no statistically significant associations were observed for p53 H-score or Ki-67 labeling index in several analyses. This may be attributable to the heterogeneous and context-dependent expression of these markers in PAs, as well as limited statistical power after subgroup stratification. Moreover, p53 and Ki-67 reflect downstream cellular responses and proliferative activity, which may not directly mirror underlying genetic susceptibility. Larger studies integrating comprehensive clinicopathological data will be required to better define their relationship with MALAT1 genetic variants.

Another limitation of this study is the lack of ancestry informative markers, which precludes formal testing for subtle population stratification. However, the relatively homogeneous ethnic background of the cohort and Hardy–Weinberg equilibrium in the control group mitigate, though do not eliminate, this concern.

The relatively small recurrence subgroup and the inability to fully distinguish true biological recurrence from regrowth of residual tumor tissue represent additional limitations of the recurrence-related analyses.

Finally, tumor invasiveness was assessed using radiological Knosp grading, which, although clinically standard, has limited sensitivity for detecting microscopic invasion. Integration of surgical and histopathological validation in future studies may therefore improve predictive accuracy.

This study highlights the potential role of MALAT1 genetic variants, particularly rs619586, in the susceptibility and clinical behavior of PAs. The rs619586 G allele was found to be significantly more frequent among PA patients compared to controls and remained associated with several aggressive tumor features, including micro- and macroadenoma formation, invasiveness, and recurrence, even after Bonferroni correction. These findings suggest that rs619586 may serve as a molecular biomarker linked to PA development and progression. In addition, a significant association between MALAT1 rs619586 genotypes and p53 expression, along with a positive correlation between p53 and Ki-67, further supports the interplay between genetic and proliferative.

factors in PA pathophysiology. Although other investigated variants (rs1194338 and rs3200401) did not show significant associations, the overall results underscore the importance of lncRNA MALAT1 in pituitary tumorigenesis. Future studies involving larger and more diverse cohorts, as well as functional analyses, are warranted to validate these associations and elucidate the molecular mechanisms linking MALAT1 dysregulation to PA aggressiveness and recurrence.