Granular cell dermatofibroma: A potential diagnostic pitfall

Abstract

Dermatofibroma, also known as "fibrous histiocytoma", is one of the most common cutaneous soft-tissue tumours. Many variants of dermatofibromas have been described and knowledge of these variations is important to avoid a misdiagnosis of a possibly more aggressive tumour. Histological features of different variants can coexist in the same lesion, but typical common fibrous histiocytoma features are generally found, at least focally, in all cases. However, when cellular changes make up the majority of the lesion, the histopathological diagnosis can become more complex and requires immunohistochemical investigations for a correct nosographic classification. We report on the case of a cutaneous fibrous histiocytoma, "granular cell" variant, found on the left leg of a 74- year-old woman.

Keywords: Dermatofibroma; Granular cell; Histiocytoma; Immunohistochemistry; Skin.

Figure 1.

A dark-brown papule of the left leg appeared one year before and slowly increased in size.

Figure 2.

The lesion was composed of a variable admixture of fibroblast-like cells and histiocytes that showed in more than 90% a large eosinophilic cytoplasm filled of granules or microvacuoles (Hematoxylin-Eosin, A: original magnification 40x; B: original magnification 200x). The neoplastic cells were strongly immunoreactive for CD68 (C: original magnification 40x) and negative for S100 protein (D: original magnification 100x).