Pigmented Bowen's disease mimicking cutaneous melanoma: clinical and dermoscopic aspects

Pigmented Bowen's disease (BD) (squamous cell carcinoma in situ) has been rarely described among white patients.

We report the case of a 48-year-old white male presenting a lesion of pigmented BD on his left thigh, clinically mimicking a superficial spreading melanoma.

Naked-eye physical examination revealed a single 1.8 x 1.5 cm, hyperpigmented plaque with a rough surface, which appeared irregularly shaped and sharply demarcated. The assessment of this uncommon tumor by means of dermoscopy, never reported in literature before, was performed. According to standardized terminology, none among the well-established dermoscopic criteria useful to discriminate between melanocytic and nonmelanocytic origin was detected within the lesion. A reticular pigmentation simulated remnants of atypical pigment network, being of uncertain diagnostic value in the preoperative classification of the lesion. Other recognized patterns were irregular, brown globular structures and wide regression-like areas. None of the features diagnostic for pigmented basal cell carcinoma was found as well.

The correct classification of nonmelanocytic origin of the lesion was therefore achieved only at histologic examination, after the complete surgical excision. In spite of its rarity, pigmented BD should be included among those lesions, which may simulate cutaneous melanoma. According to criteria validated by literature, dermoscopy failed to improve a preoperative classification of this peculiar skin tumor.