Subcutaneous mass of the forearm.

A 9-year-old girl presented with a subcutaneous mass on her right forearm that had been present for a year. The mass had initially developed after a mosquito bite and caused itching and enlargement. Topical treatments were ineffective, so a biopsy was performed. The histopathological examination revealed a fibroblastic connective tissue nevus (FCTN), a benign neoplasm of fibroblastic and myofibroblastic origin. The patient underwent excisional removal of the nevus and has not experienced recurrence since. FCTN is a rare condition that typically presents as a slow-growing plaque or nodule on the head, neck, or trunk in children. It is more common in females and is characterized by a proliferation of spindle cells without cytologic atypia or mitotic activity. It can be mistaken for dermatofibrosarcoma protuberans (DFSP), a locally aggressive soft tissue sarcoma, but DFSP has distinct histological features and a higher risk of recurrence. Other differential diagnoses include dermatomyofibromas (DMF) and fibrous hamartoma of infancy. Treatment for FCTN involves local excision, which is associated with a good prognosis and low risk of recurrence. [Extracted from the article]