Nodular fasciitis (pseudotumor of the skin)

A 34-year-old man complained of a nodule on the flexor aspect of his forearm which had been present for a year. Histopathology showed a circumscribed lesion of fascicles of spindle cells within a mucoid intervening matrix. The cells were positive for vimentin, a-actin and LU 5. The proliferation markers PCNA and Ki-67 indicated a high mitotic activity and growth rate. A diagnosis of subcutaneous nodular fasciitis (NF) was made. NF belongs to the group of inflammatory myofibroblastic tumors. The pseudotumoral clinical and histological aspect of NF may lead to misdiagnosis.