A 56-year-old woman presented with a 15-year history of an asymptomatic, slow-growing mass over her right foot. Physical examination revealed a solitary, skin-coloured, nontender, lobulated exophytic growth, 50 9 40 mm in size, over the lateral aspect of the dorsum of the right foot. The surface of the lesion was studded with multiple grain-like protrusions (Fig. 1a).Under nonpolarized contact dermoscopy, the nodule was seen to have a diffuse grey to yellow background, grey to yellow cobblestone-like areas, and a pigmented network-like area. The grain-like protrusions had grey structureless areas within them, and hairpin, linear irregular and twisted vessels around them (Fig. 1b). Magnetic resonance imaging (MRI) of the growth showed a well-defined, lobulated, exophytic, soft-tissue lesion with multiple thin internal septa, confined to the cutaneous and subcutaneous plane without any infiltration of tendon, muscle or bone (Fig. 1c).
Histopathological findingsHistological examination of a skin biopsy revealed epidermal hyperplasia, increased basal pigmentation, basaloid follicular induction and a well-defined, unencapsulated, multilobular dermal and subcutaneous mass separated by fibrous septa. The lobules were of variable size and contained spindled, epithelioid and stellate cells in a background of an abundant myxoid matrix. The epithelioid cells displayed a cord and syncytial arrangement. Immunohistochemistry showed that the cells were positive for S100 (Fig. 2).What is your diagnosis? (a) (c) (b) Figure 1 (a) Solitary lobulated exophytic mass over the lateral aspect of the dorsum of the right foot, with the surface showing multiple grain-like protrusions. (b)Dermoscopy showing yellow to grey cobblestone-like areas, grey structureless areas (*), and hairpin and twisted vessels (arrow). (c) Fat-suppressed, coronal, T2-weighted magnetic resonance imaging scan, showing a welldefined lobulated exophytic uniformly hyperintense lesion with multiple, hypointense, thin internal septa over the lateral aspect of the dorsum of the right foot confined to the cutaneous and subcutaneous planes.