Spitz naevus showing clinical features of both granuloma pyogenicum and pigmented naevus.

Abstract

Sir, Spitz naevus is a benign melanocytic lesion that shares many histological features with malignant melanoma.1 It is most common on the lower extremities and the face of children, and presents at birth only rarely. Spitz naevi most commonly appear as solitary, pinkish, asymptomatic, dome‐shaped, round to oval, firm nodules, most of which are light‐coloured and soft, and may be clinically diagnosed as granuloma pyogenicum, haemangioma or dermal naevus.2 However, pigmented Spitz naevus, or the dark‐coloured type, may be tan, brown, or even black, and thus should be differentiated from malignant melanoma and pigmented naevus.2 A 16‐month‐old Korean boy presented with a 4‐month history of a 0·5 × 0·5 × 0·5 cm pinkish‐coloured eroded dome‐shaped nodule arising on a 1·2 × 0·5 cm congenital verrucous, blackish plaque on the left side of the chest (Fig. 1a). Excisional biopsy was performed. Microscopy of the pinkish nodule showed many clusters of atypical melanocytes and increased numbers of vessels in the oedematous dermis. The lesional cells were smaller in size with increasing depth. In the centre of the verrucous, blackish plaque, there was symmetrical, well circumscribed, infiltration of atypical melanocytes in the upper dermis. There were also collections of melanophages and infiltration of lymphohistiocytes in the dermis. In the periphery of the verrucous plaque, there were nests of atypical melanocytes with some mitotic activity within the epidermis and in the dermis, with moderate melanin pigmentation. The nests were composed of spindle cells and epithelioid cells. Clefts were observed between nests of melanocytes and keratinocytes (Fig. 1b). On immunohistochemical staining, the nest cells in the verrucous plaque were positive for HMB‐45, but those in the dome‐shaped nodule were negative. They were all positive for S‐100 protein. A diagnosis of Spitz naevus was made, and the patient has been followed up for 6 months after excision without any evidence of recurrence.