Primitive pituitary perivascascular epithelioid cell tumor: A challenging diagnosis of melanocytic pituitary lesion.

Background: Perivascular Epithelioid cell tumors (PEComa) are rare mesenchymal tumors. They generally occur in the gynecologic or digestive tract. The diagnosis of Central Nervous System PEComa is exceptional and challenging.

Case Description: We report the case of a 46-year-old woman, with no particular medical history, who presented a secondary amenorrhea and a slight hyperprolactinemia. She was diagnosed on MRI with a pituitary tumor showing spontaneous hypersignal in T1-weighted images. After failure of medical treatment with cabergoline, surgical resection was required due to progressive tumor growth. Macroscopic aspect and initial immunohistochemical features were in favor of a primitive hypophyseal melanocytoma. However, molecular and transcriptional study through targeted exome- and RNA-sequencing led to the exceptional diagnosis of pituitary Perivascular Epithelioid Cell Tumor (PEComa). Three-years of postoperative radio-clinical follow-up showed an asymptomatic non-evolutive small remnant.

Conclusion: PEComa is an exceptional diagnosis among pituitary tumors. It should be evoked as a potential differential diagnosis in case of primitive melanocytic lesion of the pituitary gland. Specific molecular analysis is mandatory to confirm the diagnosis and exclude differential diagnosis.