Unusual Dual Brain Tumor Morphologies in an MEN1 Patient: A Case Report of Diagnostic Challenges and Methylation Insights

Multiple Endocrine Neoplasia Type 1 (<i>MEN1</i>) is an autosomal dominant disorder commonly associated with tumor development in the parathyroid glands, pancreas, and pituitary gland. While pituitary adenomas are frequently observed in <i>MEN1</i> patients, the presence of additional tumors within the pituitary gland is unusual. Moreover, the co-occurrence of a pituitary adenoma with an atypical teratoid/rhabdoid tumor (ATRT) has not been previously documented. ATRT is a rare, aggressive neoplasm predominantly affecting young children and is typically associated with inactivating mutations in the <i>SMARCB1</i> or <i>SMARCA4</i> tumor suppressor genes. These mutations result in uncontrolled cellular proliferation, which underlies the malignancy's rapid progression. In adults, ATRT is exceedingly rare, making this case particularly noteworthy for its uniqueness in both tumor type and patient demographics. ATRTs are now classified into three molecular subgroups-<i>MYC</i>, <i>SHH</i>, and <i>TYR</i>-each with distinct epigenetic and clinical features, further refining diagnostic and prognostic assessments. In this case report, we describe a case of a female patient with <i>MEN1</i> who experienced several recurrences of pituitary adenoma, ultimately necessitating surgical resection. Detailed pathological evaluation of the resected tissue revealed two distinct neoplasms within the pituitary gland: one typical of a pituitary adenoma, and the other confirmed as ATRT. The diagnosis of ATRT was established through extensive workup including immunohistochemical analysis, next-generation sequencing and methylation profiling, which served as essential tools in distinguishing ATRT from other potential differential diagnoses. This case illustrates the complex diagnostic journey and challenges encountered in identifying ATRT in the context of <i>MEN1</i>, underscoring the importance of using advanced molecular and immunohistochemical techniques in atypical presentations. Furthermore, it expands the understanding of potential tumor associations within <i>MEN1</i>, providing insight for pathologists and clinicians into the rare possibility of concurrent tumors in addition to pituitary adenoma in <i>MEN1</i> patients. Raising awareness of such co-occurrences could prompt earlier diagnostic considerations by refining the differential diagnosis in patients with <i>MEN1</i> presenting with unusual tumor types.