A Case of Multinucleate Cell Angiohistiocytoma with New Reflectance Confocal Microscopy Findings.

Multinucleate cell angiohistiocytoma (MCAH) is a rare, benign, vascular or fibrohistiocytic tumor usually presenting as single or multiple, reddish-brown papules mostly affecting the limbs and dorsum of the hands of middle-aged females. Since 1985, relatively few MCAH cases have been reported. In vivo reflectance confocal microscopy (RCM) findings of MCAH have never been described. We report a case of MCAH with new non-invasive imaging findings through RCM in correlation with dermoscopy and histopathology. A 66-year-old woman with an unremarkable family and personal history of an atypical nevus presented with a lesion on her right breast. It had appeared 12 months earlier and progressively enlarged. Physical examination revealed a 20 × 11.6 mm, non-tender, reddish-brown maculo-papular lesion with blurred margins. Dermoscopy showed diffusely arranged reddish areas, coalescing whitish patches, truncated and dotted vessels, and a peripheral brown reticulated pattern. RCM revealed a poorly outlined lesion with a normal honeycomb pattern, numerous vessels at the dermal-epidermal junction, and isolated, large, mildly reflective, bizarre structures with angulated edges. These findings correlated well with histological features, which established the diagnosis of MCAH. Even though histopathology remains the gold standard in the diagnosis of MCAH, non-invasive tools such as RCM can help rule out other entities, therefore reducing surgery-associated morbidity.