Cutaneous Benign Epithelioid Peripheral Nerve Sheath Tumour: A Rare Entity
A male patient aged 47 years, gives history of sudden increase in the size of a nodular lesion over the knee, following a minor trauma. The swelling had been present for the last 35 years and was slowly increasing in size. A history of trauma sustained to the site at the age of 12 was elicited, which healed with a small bleb sized lesion over the lateral end of scar. It was associated with pain following pressure at that site with full range of movements of the knee joint. Presently, the swelling had become painful following trauma to the lesion. The surgeon noted a nodular cutaneous lesion over the lateral aspect of the knee joint measuring 2.5 cm across, which was freely movable over the underlying structures. Skin over the lesion was stretched, hypopigmented and smooth []. A clinical diagnosis of sebaceous cyst was made and local excision performed. Specimen received in the pathology department was a single skin covered nodular tissue measuring 2 × 1 cm. Cut section showed a single cyst with luminal areas of haemorrhage and thick wall with solid white areas. Histopathological examination (HPE) showed a mid to deep dermal lesion with central cystic degeneration and coagulative necrosis. Short fascicles of spindle and epithelioid cells were seen [Figures and ], with moderate eosinophilic cytoplasm, vesicular fusiform nucleus, prominent eosinophilic nucleolus and an occasional mitotic figure, vaguely resembling Antoni A areas []. Areas of haemorrhage rimmed by hemosiderrin laden macrophages, stromal hyalinisation and chronic inflammation were noted. Tumor cells were S100 positive diffusely [inset [], and SMA and CD68 negative. MIB count was low. Based on these findings, a diagnosis of Cutaneous Benign Epithelioid Peripheral Nerve sheath tumor was offered.