Metastatic PEComa to the brain

Abstract

Neoplasms of perivascular epithelioid cells (PEComas) have in common the co-expression of melanocytic and muscle immunohistochemical markers. While most reported PEComas have behaved in a benign fashion, malignant PEComas have occasionally been documented [3–5]. We present a case of malignant PEComa, which was Wrst diagnosed as a brain metastasis; this represents the Wrst documentation of brain involvement by PEComa. A 53-year-old woman presented with malaise. Computerized tomography (CT) of the chest and abdomen revealed multiple lung lesions bilaterally, as well as a solitary mass in the left adrenal gland. The largest lung lesion was located in the right upper lobe and measured 5.4 £ 3.5 £ 3.4 cm, while the adrenal mass measured 4.8 £ 3.2 £ 2.9 cm. Fine needle aspiration of one of the lung lesions was interpreted as indeterminate for malignancy. The liver, pancreas, spleen and kidneys were normal by abdominal imaging. Several months later, she presented with headache, nausea and vomiting. She had diYculty with naming. A CT scan of her head revealed a mass in the left posterior temporal lobe, which was mostly solid with cystic components (Fig. 1). The patient underwent a temporal craniotomy and resection of the brain tumor. Postoperatively, neuroimaging showed no evidence of residual tumor. The patient’s headache improved and she was discharged home. Pathologic examination of resected tumor tissue showed cells arranged in sheets and nests, invested with a prominent capillary vasculature (Fig. 2a). The interface between tumor and uninvolved brain was sharp and several foci of necrosis were present. The neoplastic cells were epithelioid, with abundant cytoplasm that varied from eosinophilic and granular to clear (Fig. 2b). The nuclei were round with moderate pleomorphism and they often contained conspicuous nucleoli; mitoses were rare. Periodic acid–SchiV (PAS) staining, with and without diastase digestion, demonstrated intracytoplasmic glycogen (Fig. 2c). The biopsied lung lesion was morphologically similar to the brain tumor, although there was greater nuclear pleomorphism and more prominent nucleoli in the latter. Immunohistochemistry showed strong positivity within tumor cells for HMB45, Melan-A and caldesmon, while desmin was focally positive (Fig. 3a, b). The neoplastic cells failed to stain with antibodies against S100, tyrosinase, epithelial membrane antigen (EMA), vimentin, cytokeratin (AE1/AE3, 8/18, 7/20, 34BE12), inhibin, actin (smooth muscle and muscle speciWc), smooth muscle myosin, neuron speciWc enolase (NSE), synaptophysin, chromogranin, neuroWlament, glial Wbrillary acidic protein (GFAP), CD10, CD99, CD117, CD34, carcinoma embryonic antigen (mono and polyclonal), calretinin, heppar1 and placental alkaline phosphatase. Ultrastructural examination of glutaraldehyde-Wxed tissue revealed intracytoplasmic glycogen and lipid. Premelanosomes and desmosomes were absent. The WHO has recently oVered formal recognition to a group of neoplasms with perivascular epithelioid cell diVerentiation. This group of tumors have in common the presence of epithelioid to spindle cells with J. R. ParWtt (&) · J. L. Keith · J. F. Megyesi · L. C. Ang Department of Pathology, London Health Sciences Centre, University of Western Ontario, 339 Windermere Road, London, ON, Canada N6A 5A5, e-mail: jrparWt@uwo.ca