Rare pituitary Perivascular Epithelioid Cell tumour (PEComa)

Abstract

A 63 year old lady presented with general weakness and 4 months progressive visual disturbance. She has a family history of Birt-Hogg-Dube syndrome. Examination revealed bi-temporal hemianopia. MRI imaging showed a pituitary lesion with suprasellar extension causing optic chiasm compression. She underwent transnasal endoscopic debulking of pituitary lesion, with subsequent improvement in vision. Weakness improved with thyroxine. Histopathology showed adenoma-like tumour with evidence of melanin production. Birt Hogg Dube produces skin papules and renal carcinoma; skin biopsy of two pigmented skin lesions and CT chest / abdo / pelvis was negative. Macroscopically the lesion was fibrous and vascular with similar structure to brain, resulting in residual tumour. She presented 8 months later with sudden headache and worsening visual acuity. MRI brain revealed significant pituitary tumour enlargement with a small haemorrhagic element within. She underwent urgent re-do endoscopic debulking, with slight improvement of vision. Histopathology: positive Melan A labelling of tumour cells and patchy expression of S100 antibody. TFE3 immunohistochemistry was positive but negative with FISH (i.e. not renal carcinoma or alveolar soft part sarcoma), giving a diagnosis of sella turcica perivascular epithelioid cell tumour (PEComa). The patient completed radiotherapy treatment (55Gy33F) and her vision is now normal with subsequent reduction in tumour size. This is the second case reported of primary CNS PEComa tumour - and the first in a patient with Birt Hogg Dube syndrome. WHO defines PEComas as mesenchymal tumours composed of histologically and immunohistochemically distinctive perivascular epithelioid cells.PEComas- NOS have been reported in gastrointestinal, gynaecological, genitourinary, extremities and the skin (single reports in the heart, breast, oral cavity, orbit, and skull base).Because of the difficulty in achieving complete excision, regrowth and need for radiotherapy, we think that PEComa should be considered in cases of tumours for melanoma markers, especially if they recur.