Case Number : Case 1218 - 23 February Posted By: Guest

Bednar tumour.

Agree, Bednar tumor.

Agree.. Pigmented DFSP (Bednar) tumor..

Myxoid DFSP certainly must but high on the list but something is holding me back (obviously CD34 could help). DFSP usually have a storiform pattern and clearly distinguished collagen and elastic fibres. I thought it had a diffuse neurofibroma-like look as well (would do S100 and because of site MelanA as well although it does not look like blue naevus). A low-grade MPNST and desmoplastic melanoma are other considerations.

Hypopigmented common blue nevus.

Here is my diagnosis:

SKIN, LEFT BUTTOCK , PUNCH BIOPSY :
[b]-- DERMATOFIBROSARCOMA PROTUBERANS, PIGMENTED (BED[/b][b]N[/b][b]ÁR[/b][b] TUMOR)[/b]
[b] WITH MELANOCYTIC COLONIZATION[/b]


[center]Reference[/center]


Goncharuk V, Mulvaney M, Carlson JA. Bednár tumor associated with dermal melanocytosis: melanocytic colonization or neuroectodermal multidirectional differentiation? J Cutan Pathol. 2003 Feb;30(2):147-51. PubMed PMID: 12641795.


Micro: This lesion consists of a relatively diffuse neoplasm of relatively small and uniform cells that produce a sheet-like pattern of infiltration through the dermis. Some areas have a storiform pattern but most areas are diffuse and encase adnexal structures as well as some adipose tissue. A curious finding is the presence of pigmented cells in this lesion, many of them somewhat dendritic and a few epithelioid. This lesion abuts the surface or at least comes very close to the surface. Most of the lesional cells are epithelioid and slightly tapered. The pigmented cells within it are positive with Melan-A in the brown and red chromogen forms. CD68 is negative in those same cells. S100 protein appears to be positive within them. SOX10 with a red chromogen also appears to stain the nuclei of these cells marking them as melanocytes. These cells, however, are a very small part of the entire neoplasm. CD34, for instance, is diffusely positive throughout the lesion. Ki-67 shows an increased signal of about 5 % to 10% in the lower portion of the lesion and less staining in the superficial aspects. Factor XIIIa shows dendritic staining throughout much of the field. The elastic tissue staining shows a paucity of elastic fibers deep and an increase in elastic fibers in the mid portion of the lesion. Smooth muscle actin and desmin are both negative with the exception of blood vessels in the field.