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A 72-year-old man with a 15-year history of diabetes mellitus presented with an asymptomatic, whitish-yellow plaque on the sole of his right foot. The lesion measured 7 cm × 4.5 cm and had a verrucous surface and a peripheral hyperkeratotic collarette.
The size of the lesion had gradually increased over a 6-year period. A previous diagnosis of a plantar wart had been made, and repeated cryosurgery had been performed. Physical examination showed no evidence of inguinal lymphadenopathy. The patient had no history of infectious diseases or cutaneous malignant tumours. The differential diagnosis included carcinoma cuniculatum and diabetic ulcer. The lesion was surgically excised, and carcinoma cuniculatum was confirmed by histopathology (Figure 1).
Figure 1: Histopathologic findings of carcinoma cuniculatum. Note the presence of hyperkeratosis, parakeratosis, acanthosis and nests of well-differentiated squamous epithelium with slight atypia extending into the dermis. The lesion was surrounded by chronic inflammatory cells.
Carcinoma cuniculatum (verrucous carcinoma) is an exoendophytic type of low-grade squamous cell carcinoma that often presents as a slowly enlarging papillated tumour.1 In addition to the foot, it may also occur in the oral and anogenital regions.2 The clinical differential diagnosis includes plantar wart, amelanotic melanoma and sarcoma, and the histopathologic differential diagnosis includes keratoacanthoma and pseudoepitheliomatous hyperplasia.1–3 The standard treatments for carcinoma cuniculatum are surgical excision and Mohs' technique (serial excision for microscopic analysis), both of which are associated with a high cure rate and a low recurrence rate. Alternative treatments include curettage and electrodesiccation, cryosurgery, carbon-dioxide laser therapy and radiotherapy.3 Typically, the tumour remains indolent for years, although it may extend into the subcutaneous tissue or metastasize.1,2 Early diagnosis and treatment of carcinoma cuniculatum are crucial.
In our patient, no recurrence was seen 36 months after treatment. The presence of multiple, burrow-like openings on the surface of the lesion and a hyperkeratotic collarette should raise the index of suspicion for carcinoma cuniculatum.
Footnotes
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Competing interests: None declared.