Clinical case of ossifying fasciitis of the hand

Summary Ossifying fasciitis is a rare benign tumour similar to nodular fasciitis histopathologically, but, morphologically, composed of metaplastic bone with calcification and chondroid differentiation. This lesion may easily be misinterpreted as malignancy, clinically and histologically, because it presents as a rapidly growing mass originating from subcutaneous or deep fascial tissues. These lesions are usually located in upper and lower extremities and trunk. We present a case in which, unusually, it was located in the flexor tendon sheath of the hand, which caused limitation of motion. Clinical suspicion and accurate histopathology of this rare benign lesion is important because it is commonly misdiagnosed as a malignancy and results in unnecessary aggressively wide resection.