Large plaque-type blue naevus with subcutaneous cellular nodules

Summary We report a new case of ‘large plaque-type blue naevus (PTBN) with subcutaneous cellular nodules’ involving the breast. A 25-year-old-woman presented with a large plaque, 140 × 100 mm in size, on the right chest wall involving the right breast, associated with recent subcutaneous nodules. Histopathological examination revealed features of cellular and common blue naevus. Dermatoscopy was performed, and the diagnosis of PTBN was made. PTBN is a rare condition with an imprecise prognosis. In cases of PBTN lesions on the head, clinicians must keep in mind the risk of malignant transformation of PTBN or an association with cutaneous neurocristic hamartoma. For this new variant of PTBN appearing on the trunk, we propose close monitoring of the patient if surgical excision is impossible.