The latter, also called Bednar tumour (BT), differs from typical DFSP by the presence of characteristic melanin-pigmented dendritic cells.
Caption: Figure 1: Microscopic features of Bednar tumour. (A and B) The tumour is composed of monomorphous spindle shaped cells in a prominent storiform pattern, infiltrating the hypodermal fat in a characteristic "honeycombing" pattern.
Caption: Figure 2: Immunohistochemical features of Bednar tumour. (A) Tumour cells are diffusely positive for CD34.
DFSP variants Yimentin S100 CD34 Classic + - + Myxoid + - - Bednar tumour + - (+ pigmented + cells) Fibrosarcomatous + - - Atrophic + - + Myoid + - - Giant cell fibroblastoma + - + (may be weak) DFSP variants [alpha]-actin HHF35 Desmin Classic - - - Myxoid - - - Bednar tumour - - - Fibrosarcomatous - - - Atrophic - - - Myoid + + - Giant cell fibroblastoma - - - Table 2: Bednar tumour: differential diagnosis by immunohistochemistry (SCC: squamous cell carcinoma; MM: malignant melanoma; SS: synovial sarcoma).
Bednar tumour, first described by Bednar in 1957, is a pigmented variant of dermatofibrosarcoma protuberans (DFSP).It is a rare entity, constituting 1 to 5% of all DFSPs, which in turn, represent 0.1% of skin malignancies.
Thus, a final diagnosis of Bednar tumour was rendered.
These include Bednar tumour, fibrosarcomatous, fibrosarcomatous with myoid/myofibroblastic change, myxoid, granular cell, palisaded, giant cell fibroblastoma, combined and indeterminate.
Pigmented DFSP (Bednar tumour), first designated as storiform neurofibroma by Bednar, is a clinically and morphologicallydistinct variant of DFSP, constituting 5%-10% of all cases of DFSP.
The histogenesis of Bednar tumour is controversial.
Histopathologically, Bednar tumour is characterised by scattered melanosome-containing dendritic cells within an otherwise typical DFSP.
Pigmented neurofibroma can be differentiated from Bednar tumour by more extensive storiform growth and strong positivity for CD34 in latter.