A Case of Intradermal Nevus with Pseudovascular Space

Abstract

Melanocytic nevus may be histologically associated with cleft of nests resembling vascular space. This pseudovascular space mainly has been known as an artifact of tissue processing and may simulate the lymphatic invasion of malignant melanoma. It is important to be aware of this histologic variant in melanocytic nevus to prevent the misdiagnosis. We report a 38-year-old female who had a melanocytic nevus on her back since childhood. This nevus gradually enlarged with erythematous swollen border for several months. Histopathologic examination represented an intradermal melanocytic nevus. Nevus cell nests were clustered in the dermis and vascular-like spaces were seen in the nevus cell nests. Immunohistochemical staining showed that cells lining the pseudovascular space were positive for S-100 protein and negative for smooth muscle actin, factor Ⅷ-related antigen, and CD34. We conclude that these spaces are lined by nevomelanocytes and that the spaces are not truly vascular.