Case of dermatofibroma with monster cells: a review and an immunohistochemical study.

We report a dermatofibroma with monster cells. The patient was a 79-year-old woman who had a dark-brown nodule of her left leg for approximately 3 years. The lesion was composed of spindle-shaped fibroblastic cells, histiocytic cells, and multinucleated giant cells. Most of the histiocytic cells had foamy cytoplasm with numerous hemosiderin deposits. In addition to these cells, bizarre multinucleated cells with markedly hyperchromatic nuclei and xanthomatous cells with very large nuclei (monster cells) were also noted. No mitotic figures of the cellular components were present. This lesion has been shown to be completely benign despite the presence of pleomorphic or bizarre cells. From a clinical standpoint, recognition of a benign lesion of this type is very important since an incorrect histologic interpretation could result in inappropriate treatment.