FIBROSARCOMATOUS (HIGH-GRADE) DERMATOFIBROSARCOMA PROTUBERANS - CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY OF A SERIES OF 41 CASES WITH EMPHASIS ON PROGNOSTIC-SIGNIFICANCE

The fibrosarcomatous variant of dermatofibrosarcoma protuberans (FS-DF SP) represents an uncommon form of DFSP, in which the prognostic influ ence of the fibrosarcomatous component is still debated. We analyzed t he clinicopathologic and immunohistochemical features in a series of 4 1 patients. Patient age ranged from 8 to 87 years (median, 48 years, a nd 19 patients were female. Twenty five lesions were seen on the trunk , 6 on the upper limbs, and 4 on the lower limbs, and five neoplasms w ere located in the head/neck region; in one case, exact anatomic sire was unknown. Twenty seven tumors involved purely dermal and subcutaneo us tissues, in 10 casts, deeper structures were also involved, 1 case arose in the breast, and, in 3 cases, it was impossible to define exac t depth of the lesion. Preoperative duration ranged from 1 month to 60 years (median, 3 years). Twenty six tumors were excised locally with clear margins, 7 were treated by wide excision, 3 by incomplete excisi on, and, in 4 patients, the lesion was shelled our. In one case, exact treatment was unknown. in addition, radiotherapy was administered in three cases and chemotherapy in one case. Histologically, the lesions showed areas of typical, low-grade DFSP adjacent to fibrosarcomatous a reas. Ln four cases, a previously ordinary DFSP recurred as pure fibro sarcoma, in two cases, local recurrence of FS-DFSP showed features of ordinary DFSP. Fibrosarcomatous change was more common in the primary (de novo) lesions than in recurrent lesions (3.6:1). Proportion of fib rosarcoma varied between < 30% in 6 cases to > 70% of tumor tissue in 21 cases. An abrupt transition between both components was seen in 19 cases. The fibrosarcomatous component showed focal necrosis in seven c ases and showed a higher mitotic rate in comparison with ordinary DFSP areas (mean, 13.4 versus 2.3 mitoses in 10 high-power fields). Additi onal histologic features included progression to pleomorphic sarcoma i n 2 recurrent cases, melanin-pigmented cells (Bednar FS-DFSP) in 1 cas e, focal myxoid change in 13 cases, plaque or keloidlike hyalinization in 3 cases, and myoid bundles and nodules in 9 cases. Immunohistochem ically, tumor cells in DFSP areas stained positively for CD34, whereas , in FS-DFSP areas, only 15 out 33 cases were positive for CD34. Follo w-up in 34 of 41 patients (mean, 90 months; median, 36 months) reveale d local recurrence in 20 patients (58%) (recurrence occurred in 5 pati ents on two or more occasions), Metastases (5 lung. 1 bone, and 1 soft tissue) were seen in 5 patients (14.7%). and 2 patients have died of tumor to date (5.8%). Necrosis, high mitotic rate (> 10 mitoses per 10 high-power fields), and presence of pleomorphic areas in FS-DFSP tend ed to be related with poor clinical outcome, but no statistically sign ificant association was detected. Fibrosarcomatous change in DFSP repr esents a form of tumor progression in DFSP and is associated with a si gnificantly more aggressive clinical course than in ordinary DFSP, ind icating a possible need for treatment intensification in such cases.