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Malignant extraneural soft tissue perineurioma with striking microvascular proliferation.

Sir, Perineurioma is an uncommon variant of peripheral nerve sheath tumour composed predominantly of perineurial cells. Malignant perineurioma is exceedingly rare. A case of malignant extraneural soft tissue perineurioma is described which arose on the lower left leg of an 83-year-old woman. There was striking microvascular proliferation, which seems to be a novel feature in this case. The palpable mass of unclear duration, measured 53 36 7 mm at ultrasound and was determined to be solid, hypoechoeic, heterogeneous, and to reside in the deep subcutaneous layer, superficial to fascia and adjacent to the tibialis anterior muscle. The surrounding adipose tissue was reported to appear oedematous and hyperaemic. Diagnostic and attempted excision biopsy was performed and the laboratory received three nodular pieces of grey/white rubbery mucoid tissue and adipose tissue measuring 25 20 8 mm in aggregate dimension following fixation in 10% neutral buffered formalin. Histologically (Fig. 1) there were multiple fragments of a nodular, variably cellular myxoid tumour, which was mostly well defined, but focally intermingled with adipose tissue. The tumour was composed of spindle cells with elongated nuclei and delicate long thin biphasic cytoplasmic processes arranged in a fascicular and somewhat wavy and whorling lamellar fashion in a predominantly myxoid background. There was variable nuclear atypia ranging from mild through to marked with highly pleomorphic and multinucleated tumour cells,