Bednar tumour

Bednar tumour

A form of dermatofibrosarcoma protuberans (DFSP) that contains heavily pigmented (melanin) dendritic cells, which contrasts with dermatofibromas which contain haemosiderin pigment.
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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.
Unusual variants of DFSP include the Bednar tumour that is denoted by melanin- containing cell, myxoid DFSP that contains areas of interstitial mucin, and the atrophic type.