Introduction: Pituitary adenomas are the most common pituitary tumours, but in 18% of cases we can find other rare tumours like: Rathkes cleft cyst, craniopharingyomas, chordomas, meningiomas, infiltrative or infectious disease. Meningeal melanocytoma is a benign neoplasm of central nervous system, commonly located in the base of the brain, cerebellopontine angle and the pineal body, difficult to differentiate from a nonfunctional pituitary adenoma before surgery.
Case report: We present the case of a 63-year-old man who presented 15 years ago for the evaluation of a nonfunctional pituitary adenoma. He developed sudden onset unilateral hemianopsia, and the MRI exam revealed a voluminous sellar and parasellar mass, protrusive in the sphenoid and cavernous sinuses. Partial transfrontal resection of the tumor was performed, and the pathology and immunohistochemistry diagnosed a null cell nonfunctional pituitary macroadenoma. Due to the presence of a progressing, large, residual mass, radiotherapy was recommended and performed and the patient developed global hypopituitarism. After radiotherapy the patient presented with initial tumor regression, but in the following 14 years the tumor progressed, with narrowing of the visual field, requiring a new neurosurgical, transsphenoidal resection. The pathology revealed meningeal melanocytoma, and the diagnosis was confirmed by immunohistochemistry: positive for melan A, S-100 and HMB45 and negative for CK19, CK20 and GFAP, with low-grade proliferation risk Ki-67 = 12%.
Conclusions: The association between meningeal melanocytoma and nonfunctional pituitary adenoma it is uncommon and represents a challenge for diagnostic and treatment. The gold standard therapy is complete surgical resection, but in cases with large residual tumoral mass or high proliferation risk, high-dose radiotherapy is recomended. Although benign, the meningeal melanocytoma can occasionaly relapse and present with malignant transition, so careful imaging surveillance is recommended.