Intradermal melanocytic nevus with lymphatic nevus cell embolus: A case report.

The current study presents a rare case of intradermal melanocytic nevus with lymphatic nevus cell embolus. A 26-year-old male presented with a slowly enlarging, pigmented nodule on the back, measuring 1 cm in diameter. Histological observations of the lesion were typical of an intradermal melanocytic nevus. The most notable feature of this nevus, however, was an aggregate of nevus cells within a lymphatic vessel of the upper dermis. The nevus cells observed within the lymphatic lumen demonstrated characteristic morphological features of type A nevus cells. The cells were round-to-cuboidal, exhibited abundant cytoplasm with well-defined cell borders and formed nests. In addition, the nevus cell aggregate was lined by flattened endothelial cells. Nevus cell aggregates occur in the collagenous framework of lymph nodes, however, the mechanism by which nevus cells are deposited in lymph nodes has been a source of interest and controversy. The histological observation presented may be regarded as support for the mechanical transport or benign metastasis theories, which posit transfer of nevus cell emboli, via lymphatics, from a cutaneous nevus to the draining regional lymph node. Due to its rarity, a lymphatic nevus cell embolus creates diagnostic and management issues for pathologists and clinicians. This observation must not be interpreted as evidence of malignancy, but must be assessed in context with the associated histological features of the lesion.