Ectopic prolactin secretion from a perivascular epithelioid cell tumor (PEComa)

The diagnosis of ectopic pituitary hormone secretion requires abnormally high circulating hormone levels, absence of a pituitary tumor, and localization of the hormone in question to the extrapituitary malignant neoplasm. No case of a malignant solid tumor producing prolactin has been documented thus far.

A 47-year-old woman presented with amenorrhea and galactorrhea of 3-year duration. Serum prolactin ranged from 300 to > 900 ng/mL, and other pituitary and thyroid indices were normal, including testing for macroprolactinemia. Pituitary magnetic resonance imaging revealed a partially empty sella but no tumor. Cabergoline 0.5 mg twice weekly did not affect her prolactinemia (1700 to 1900 ng/mL), and the medication was stopped. In the meantime, she developed abdominal pain, and a computed tomography scan showed a 17 × 13 × 8-cm mass abutting the distal stomach, proximal duodenum, and right colon. After the tumor was excised, her galactorrhea resolved, menstrual periodicity resumed within the first month, and serum prolactin fell to 5 ng/mL. Pathological examination of the excised tumor was consistent with perivascular epithelioid cell tumor. Between 5 and 10% of the tumor cells were strongly positive for prolactin on immunohistochemistry. RT-PCR detected prolactin mRNA in the tumor cell extract, confirming the diagnosis of ectopic prolactin synthesis and secretion.

We present the first example of massive and symptomatic hyperprolactinemia due to ectopic prolactin production by a solid extrapituitary mesenchymal tumor confirmed with both mRNA analysis and immunohistochemistry. Ectopic prolactin secretion should be suspected in patients with a prolactin >200 ng/mL and negative sellar MRI.