This type of tumor is encountered most frequently by the general pathologist as an excised mass. The dermatopathologist will see an occasional case since there may be involvement of the deep dermis, particularly in cases involving the distal aspect of a finger. When encountered in a skin specimen, the tumor is sharply circumscribed and there may be a suggestion of lobulation. The basic cell population is a round or polygonal histiocytic or fibrohistiocytic cell.
Giant cells are usually present, but the number is quite variable from case to case.
Ordinary histiocytic giant cells may be seen, and osteoclastic type giant cells may also be present. Foamy histiocytes and hemosiderin laden histiocytes are seen in some cases. Scan power view. The tumor is much more sharply circumscribed than a dermatofibroma. There is a suggestion of lobulation that is created by the presence of fibrous septa that curve within the tumor.