Chromosomal translocation abnormalities in the tumor cells involving chromosomes 17 and 22 resulting in the fusion gene COL1A1-PDGFB have been reported in DFSP. This translocation causes an overproduction of the protein platelet-derived growth factor, resulting in tumor growth.
Lesions are most common in the trunk and proximal extremities. Less commonly, the head and neck may be involved. Lesions present as painless slow-growing red-brown nodules that may become painful as they enlarge. The differential diagnosis for early DFSP includes large dermatofibroma, keloid, dermatomyofibroma, and morphea. DFSP in childhood tends to appear more atrophic. It may be difficult to diagnose DFSP if the initial biopsy is superficial. If clinical suspicion is high, rebiopsy, ideally into the fat, is recommended.
Histologically, there is a cellular proliferation of thin spindled fibroblasts and collagen in the dermis that extend into the fat, often in a multilayered pattern. Adnexal structures can be obliterated. Fibroblasts may form a cartwheel or storiform pattern. There is mild cytologic atypia. Fibrosarcomatous change may signal increased risk of metastasis. CD34 is often positive and factor XIIIa is negative, unlike in dermatofibroma, which is opposite. Forms of DFSP that can be seen histologically include atrophic DFSP (flat rather than nodular), myxoid DFSP, and pigmented DFSP (also known as Bednar tumor).
DFSP can have irregular shapes with extensions into the fat. Subsequently, DFSP has a high recurrence rate with traditional surgical removal. Mohs surgery is now the treatment of choice. Recurrent tumors should be resected. As metastasis is rare, further work-up is not routinely indicated unless history and physical examination warrant it.(Gleevec), which targets the platelet-derived growth factor receptor, has been tried with patients with inoperable or metastatic DFSP with some success. Radiation may also be used as an adjuvant after surgery. Regular follow-up exams with examination of the surgical site for possible recurrence should be performed every 6-12 months.
This case and photo were submitted by Dr. Bilu Martin.
Dr. Bilu Martin is a board-certified dermatologist in private practice at Premier Dermatology, MD, in Aventura, Fla. More diagnostic cases are available at mdedge.com/dermatology. To submit a case for possible publication, send an email to [email protected].