Unmasking Dermatofibrosarcoma Protuberans: Clinical Considerations Post‐Surgical Excisions

Abstract

Introduction Dermatofibrosarcoma protuberans (DFSP) is a rare (prevalence = 0.8–4.5 cases / 1 million) malignant tumor of cutaneous soft tissue. Typical clinical presentation involves an asymptomatic, slowly enlarging indurated plaque, involving the dermis and soft tissues, usually on the trunk. Overlying skin can show telangiectasias, sclerodermiform changes, and reddish‐brown discoloration. DFSP is invasive; irregular, tentacle‐like projections lends to difficulty in border delineation, and consequently, surgical excision margins. DFSP is histologically described as spindle‐cells in whorled or storiform pattern, with uniform, small elongated cells, which stain CD34+. Case A 68‐year‐old Caucasian male presented with a chest mass. 3 years prior, the patient presented with a mass at the same location, subsequently diagnosed as a lipoma and excised. The patient has a history of diffuse B cell lymphoma, for which he completed chemotherapy. On physical exam, a mass was palpated (right upper chest, right 1st intercostal space, midclavicular, under scar from previous excision, deep to skin), with no discoloration, telangiectasia, or visible raised nodules. Patient denied pain or tenderness associated with the mass. CT and MRI were conducted, and a mass was noted. Surgical excision was performed to ensure clean margins. Within the excised specimen, a firm nodule was found, measuring 1.6cm × 1cm × 0.7cm. Microscopic examination with H&E staining showed whorled myoid with spindled nuclei in storiform array throughout the dermis, extending into subcutaneous fat with widening fibrous septa. The specimen was composed of uniform, small elongated cells and scant cytoplasm with frequent mitotic figures. Giant cells were also present, for consideration of fibroblastoma. The sample was negative for pigments, stained CD34+, and diagnosed as DFSP. The patient was referred to interventional radiology for radiation therapy with imatinib. Close follow‐up is necessary due to high recurrence rate of DFSP. Discussion This case defies many common characteristics of DFSP. First, the lesion was subcutaneous, not raised, and deep to the dermis. It also lacked telangiectasia or discoloration, characteristics of disease development. The atypical presentation may be linked to the patient’s immunosuppressed status, to scar tissue from previous excision, which masked tumor development, or to former misdiagnosis. The patient presented within the DFSP recurrence window from when the lipoma was removed, which raises suspicion. The lipoma is being re‐examined, with transformation to DSFP for consideration. Conclusion DFSP is a rare tumor of the skin and subcutaneous tissue. Though it commonly presents with induration, skin discoloration, and telangiectasias, it is important to keep DFSP as a differential in new masses found on previous surgical sites, especially if the previous mass had a possibility of recurrence. DFSP H& E stain. Storiform array with mitotic figures. DFSP Immunohistochemical stain for CD34 positive in whorled pattern