Myxoid dermatofibrosarcoma protuberans with fibrosarcomatous features

Case Report: A 64 year old presented with multiple nodular lesions on her abdomen. Initial biopsy was consistent with the high grade fibrosarcomatous variant of dermatofibrosarcoma protbuerans (DFSP). Later excision of this nodule showed areas with the usual storiform spindle cell appearance of DFSP and other areas of prominent myxoid matrix with loss of the storiform pattern. There were no remaining high grade areas in this sample and the appearances were in keeping with a diagnosis of myxoid dermatofibromasarcoma protuberans. In keeping with the diagnosis of DFSP, immunohistochemistry was positive for CD34 and negative for S100 protein.
Discussion: DFSP is a rare low-grade cutaneous malignancy. It shows a highly infiltrative growth pattern with irregular borders extending into surrounding and deep tissues. It has a propensity for local recurrence requiring aggressive surgical resection with widely negative margins (2-3cm). Radiotherapy and tyrosine kinase inhibitors may be used in certain situations for unresectable or recurrent tumours.
Typical DFSP is characterised by spindle cells in the deep dermis arranged in a storiform pattern with infiltration of finger like projections into adjacent tissue. Histologic variants of DFSP include the myxoid variant and the fibrosarcomatous variant (DFSP-FS).
DFSP-FS shows increased cellularity and cytologic atypia. Patients with fibrosarcomatous changes should be more closely monitored, as they have an increased risk for distant metastasis. Myxoid DFSP contains the classic features of DFSP but also contains cells arranged in a haphazard pattern within abundant pale myxoid stroma. Myxoid DFSP with focal fibrosarcomatous change is an extremely rare variant of DFSP.

Dr. Leonard Timoney