A case report of a primary intracranial supratentorial neuroenteric cyst in a patient with a history of lung adenocarcinoma

Neuroenteric cysts (NECs) are rare, benign, endodermally derived lesions, most commonly spinal and infrequently intracranial. Supratentorial NECs are exceedingly rare and diagnostically challenging due to their radiologic and histologic overlap with cystic neoplasms and metastases. Malignant transformation is exceptionally rare. We present a unique case of a 68-year-old male with a history of recurrent lung adenocarcinoma who developed a new-onset focal seizure and right-sided weakness. MRI revealed a multiloculated cystic lesion in the right central sulcus. Gross total resection was achieved, and histopathology showed a benign multiloculated NEC with mucin production, focal TTF-1, CK7, and MUC5 positivity. The possibility of metastasis was excluded through immunohistochemistry, systemic imaging and long-term follow-up, which showed no evidence of recurrence or systemic disease. This is the first reported case of a supratentorial NEC with focal TTF-1 and MUC5 expression in a patient with prior lung cancer, without evidence of metastasis. This case expands the immunohistochemical spectrum of supratentorial NECs and underscores the importance of rigorous differential diagnosis in patients with known malignancies.