Rapidly evolving giant dermatofibroma

Abstract

Dermatofibroma, also known as "fibrous histiocytoma", is a benign dermal or subcutaneous poorly circumscribed proliferation of spindle-shaped fibroblasts and macrophages in the dermis. Although it is commonly present as a brownish nodule the legs of females, it may also arise on the upper extremities, trunk, and rarely on the head. The exact pathogenesis is unclear. However, it is widely believed that the originating insult to the dermis is a folliculitis, an arthropod bite, or an unspecified initial inflammatory condition. Giant dermatofibromas of greater than 5 cm in diameter are rare, with only 22 cases reported in the literature. We present a case of a rapidly evolving pedunculated mass in the groin of a male patient. Histological examination confirmed this to be a giant dermatofibroma. Though this specimen cannot is not confirmed as such, the cellular subtype is sometimes present as a larger lesion with anecdotal reports of local recurrence and distant metastases. The clinical and radiological features which were somewhat suspicious of malignancy are considered in the context of the definitive pathological diagnosis of a benign lesion.

Figure 1

Anterior view of dermatofibroma (10.5 cm  ×  10 cm  ×  6 cm) in the right inguinal region. Ulcerated area is covered with tegapore dressing.

Figure 2

Axial computed-tomography view of dermatofibroma (arrowed) arising from the skin of the right base of the scrotum demonstrating a complex cystic structure with fluid and septations.

Figure 3

Excised tissue, sliced longitudinally, showing cystic and haemorrhagic areas.

Figure 4

On low power the lesion is composed of spindled cells in the dermis with a well defined Grenz zone; H&E stain, moderate magnification ×40. On high power, bundles of interlacing spindle cells in the dermis. H&E stain, magnification ×100. Same area of lesion as in (b) stained for Factor XIIIa, showing diffuse staining with scattered strongly positive cells; Factor XIIIa stain, magnification ×100. High powered section of specimen showing cholesterol clefting and scattered giant cells; H&E stain, magnification ×100