Melanoma and Clark naevus in collision tumours with a dermatofibroma

Abstract

noma include constant trauma and irritation and chronic infection. The role of human papilloma virus has also been described, although it is controversial. Verrucous carcinoma has been rarely described at sites of chronic inflammatory dermatoses like ulcerative lichen planus, lupus vulgaris, burn scars and varicose ulcers. In a study from Thailand, pesticide use was found as a contributing factor in the development of squamous cell carcinoma in plantar ulcers of leprosy. In an Indian study of 11 cases of trophic ulcers in leprosy, one patient was reported with verrucous carcinoma, while the remaining 10 cases developed squamous cell carcinoma. The annual incidence rate of squamous cell carcinoma in patients with leprosy (with disability grade 1 and 2) is reported as 0.79:1000. The risk is highest in the borderline tuberculoid group. The tumour is usually well-differentiated and metastasises late. Incisional biopsy, which is large and deep enough, is essential for accurate diagnosis as punch biopsy specimen may be too superficial. Multiple biopsies are sometimes needed to confirm the diagnosis. Histopathological examination of the tumour demonstrates both exophytic and endophytic growth patterns. The epidermis shows hyperkeratosis, parakeratosis and papillomatosis. Broad blunted projections of large, well-differentiated, pale-staining keratinocytes extend into the dermis with a bulldozing effect. There is minimal cytologic atypia and mitotic activity. The tumour is locally aggressive and can invade the underlying bone, tendons and muscle. Though it can spread to the regional lymph nodes, distant metastasis is not observed. Magnetic resonance imaging should be done to determine the extent of the tumour. The treatment is a complete surgical excision with at least 5-mm margin of healthy tissue. In large tumours or poorly differentiated cases, amputation of the toe or even the foot may be required. Radiotherapy is contraindicated as it can lead to rapid anaplastic transformation. The present case emphasises that long-standing, neglected neuropathic ulcer in leprosy may be a predisposing factor for the development of verrucous carcinoma. The majority of reported cases are of squamous cell carcinoma arising in chronic ulcers of leprosy and verrucous carcinoma as in our patient is rare in such a setting. As weight-bearing area was affected, repeated trauma due to sensory loss and resulting chronic inflammation are likely to have contributed to malignant transformation.