Ossifying fasciitis.

A case of ossifying fasciitis occurring in the left femoral region of a 57-year-old male is reported. The patient complained of pain in his left lower extremity which was the site of previous catheterization. During a left femoropopliteal by-pass, a firm and cylindric mass measuring 5 x 3 x 2.5 cm in size was found and extracted from the left groin. Histologically, a reactional lymph node and an irregularly shaped lesion extended into the perinodal fat tissue which is composed of proliferating fibroblasts with occasional mitotic activity. Within this fibroblastic proliferation, immature woven bone composed of osteoid with calcification and chondroid differentiation were seen. Metaplastic bone is an uncommon finding in cases of nodular fasciitis, parosteal fasciitis, cranial fasciitis and florid reactive periostitis. Ossifying fasciitis is known as an uncommon variant of nodular fasciitis. It is an uncommon post-traumatic benign lesion of subcutaneous tissue with an unclear etiology of ossification which is neither related with a bony structure nor contains any muscle tissue. This lesion has been reported only once previously, in the femoral region after a trauma history of catheterization.