Clinical Discussion:
Dermatofibrosarcoma protuberans (DFSP) is a sarcoma of fibroblast origin. It is most commonly seen as an acquired lesion in 40-50 year old age group, but congenital lesions can occur. It is more commonly seen in African Americans. It most often presents as slow growing, red-brown smooth nodules. The most common location is on the trunk, and DFSPs exhibit low metastatic potential but high rates of recurrence. Most tumors are found to have a t(17;22) translocation, which is thought to be a driving mutation. Excisional biopsy with subcutaneous fat is the gold standard for diagnosis. Treatment is recommended with Mohs(preferred) or wide local excision with 3 cm margins due to high rate of recurrence.
Microscopic Discussion:
Dermatofibrosarcoma protuberans (DFSP) is characterized by a diffuse proliferation throughout the entire dermis and into the underlying adipose of a monomorphous population of spindled cells that are arranged in a “storiform” or “cartwheel” pattern. Tumor cells replace the subcutis and may extend deep into the underlying soft tissue. Cellular dermatofibroma (DF) may have a very similar arrangement of bland spindled cells in a storiform pattern that mimics or closely resembles DFSP; DFSP however frequently demonstrates thinning and effacement of the overlying dermis and deep infiltrate with replacement of the fat by tumor cells while cellular DF will have overlying epidermal hyperplasia and may touch the fat, but not extend deeply and replace the fat with lesional cells. Since the majority of DFSP are characterized by t(17;22)(q22;q13) (COL1A1;PDGFB) translocation that is not seen in cellular DF, fluorescence in situ hybridization studies that demonstrate this translocation in small specimens where the diagnostic features may not be apparent.