DERMATOFIBROMA VARIANT CONTANING ATYPICAL CELLS AND GLASSY PERIVASCULAR COLLAGENOUS RINGS
A small percentage of dermatofibromas  (histiocytomas or benign fibrous histiocytomas) contain a focus or foci within which glassy collagenous rings surround small blood vessels. Such a focus is usually in the superficial part of the dermatofibroma, but the location can be elsewhere. At least some of the  'rings'  represent perivascular cylinders around tortuous vessels. Some of the cylinders have branching outlines. In this case, these structures are found mostly around the periphery of a central area of hemorrhage.There are atypical cells in this case reminiscent of the 'monster cells' that have been described in other dermatofibromas.

Because of the location and the atypical histiocytes, it could be argued that the present case is an atypical fibroxanthoma, but the glassy perivascular collagenous rings have not been described in atypical fibroxanthomas. It is interesting that an almost identical case located on an ear was sent to me about the same time that I was preparing this case for presentation.


From the ear of a 78 year old male:
 
Scan power view.
A medium power view from the right side of the scanned view. Thick, glassy, collagenous rings surround small blood vessels.
Another medium power view from the right side of the scanned view. A multinucleated histiocyte is demonstrated in addition to the collagenous rings. Spindle cells having fibroblastic features are also seen.
Medium power view showing a perivascular cylinder (CYL) of glassy collagenous material in addition to a perivascular 'ring'. Some of the 'rings' represent cross sections through tortuous vessels surrounded by the cylinders.
A high power view from central portion of the scanned view. The pigment is hemosiderin. A glassy collagenous ring is present. Many of the mononuclear cells are atypical cytologically.
Another high power view from this area. Atypical mononuclear and multinucleated cells are found in an area of hemorrhage and hemosiderin deposition.

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