Clinical course of the patient and histological findings

ARTICLE

A 50-year-old man presented with a large tumour on the left shoulder. The lesion was present and slowly growing for ten years. Anamnesis did not reveal any possible etiological factor or previous trauma. At the time of presentation, the tumour measured 14 x 13 x 12 cm, superficial ulcerations were noted but the lesion remained asymptomatic (Fig. 1). Both CT scanner and MRI described an exophytic mass without signs of infiltration of the deepest structures. No enlarged lymph nodes were noted on clinical examination or imaging. General screening was negative for disseminated disease.

The lesion was completely removed by excisional surgery and the defect was covered with a pedicled muscular pectoralis major flap associated with split thickness grafts.

Clinical course of the patient and histological findings

Adjuvant radiation therapy was administered because of the sarcomatous component of the tumour and no recurrence occurred within a follow-up period of one year.

Histological examination

The tumour presented a mixed histological pattern with areas of classical dermatofibrosarcoma protuberans merging with more cellular, fascicular areas (Fig. 3). Areas of classical dermatofibrosarcoma protuberans were composed of uniform spindle-shaped tumour cells with slender nuclei arranged in a storiform growth pattern. A diffuse honeycomb infiltration into underlying fatty tissue was seen. Higher grade areas were characterised by the presence of an increased cellularity, a fascicular architecture in a herringbone pattern, reminiscent of fibrosarcoma and an increased mitotic rate. The underlying fascia was not invaded by the tumour. On immunohistochemistry, CD34 staining was focally positive.

Fibrosarcomatous variant of dermatofibrosarcoma protuberans

Discussion

The fibrosarcomatous variant of dermatofibrosarcoma protuberans is considered as a rare lesion, probably less than 10% of all dermatofibrosarcoma protuberans cases [1-5]. Fibrosarcomatous areas are characterised histologically by long fascicles of spindle-shaped tumour cells with higher cellularity and increased mitotic activity [1]. The presence of fibrosarcomatous areas in dermatofibrosarcoma protuberans may raise additional problems in differential diagnosis (fibrosarcoma, monomorphic synovial sarcoma...) [1-5]. However, immunohistochemistry could help in differentiating the true dermatofibrosarcoma protuberans with the fibrosarcomatous variant from classical dermatofibrosarcoma protuberans or other tumors.

It is generally considered that "classical" dermatofibrosarcoma protuberans is a low-grade tumour that is only locally aggressive and rarely metastasises. However, a significantly higher rate of systemic metastases (up to 15%) and/or tumour-related deaths was noted in association with the fibrosarcomatous variant of dermatofibrosarcoma protuberans [1-5]. Moreover, a higher local recurrence rate is associated with fibrosarcomatous dermatofibrosarcoma protuberans, even after complete removal confirmed on histological examination [4]. It should also be questioned if "classical" dermatofibrosarcoma protuberans with metastases were not in fact fibrosarcomatous variant in which the fibrosarcomatous areas were not clearly identified. This variant should be regarded as a clinically significant progression from low-grade "classical" dermatofibrosarcoma protuberans and should be considered as a fully malignant soft tissue neoplasm.

What the exact signification concerning treatment modalities is remains unclear from the literature but might provide a rational basis for a more aggressive surgical treatment and certainly a close follow-up [1-5].

References

1. Mentzel T, Beham A, Katenkamp D, Dei Tos AD, Fletcher CDM. Fibrosarcomatous ("high-grade") dermatofibrosarcoma protuberans. Clinicopathologic and immunohistochemical study of a series of 41 cases with emphasis on prognostic significance. Am J Surg Pathol 1998; 22: 576-87.

2. Connelly JH, Evans HL. Dermatofibrosarcoma protuberans. A clinicopathologic review with emphasis on fibrosarcomatous areas. Am J Surg Pathol 1992; 16: 921-5.

3. Ding J, Hashimoto H, Enjoji M. Dermatofibrosarcoma protuberans with fibrosarcomatous areas. A clinicopathologic study of nine cases and comparison with allied tumors. Cancer 1989; 64: 721-9.

4. Diaz-Cascajo C, Weyers W, Borrego L, Inarrea JB, Borghi S. Dermatofibrosarcoma protuberans with fibrosarcomatous areas: a clinicopathologic and immunohistochemic study in four cases. Am J Dermatopathol 1997; 19: 562-7.

5. Morimitsu Y, Hisaoka M, Okamoto S, Hashimoto H, Ushijima M. Dermatobibrosarcoma protuberans and its fibrosarcomatous variant with areas of myoid differentiation: a report of three cases. Histopathology 1998; 32: 547-51.