Cellular blue nevus with massive regional lymph node metastases

Small, well-differentiated groups of nevus cells have been found occasionally in the marginal sinuses and parenchyma of regional lymph nodes that drain sites of cellular blue nevi.<br> The histologic, immunohistochemical, and karyometric description of a pigmented cutaneous lesion, with the features of cellular blue nevus and located on the leg of a 14-year-old woman, that was accompanied by synchronic presentation of massive inguinal lymph-node metastases.<br> The excised specimens were processed routinely, embedded in paraffin, and sectioned into 4-microm-thick slices. The sections were stained using hematoxylin-eosin and the ABC immunohistochemical method for demonstrating S-100 and HMB-45. Karyometric analysis was performed in a static cytometer using Feulgen-stained sections.<br> The cutaneous lesion had the cytologic and architectural features of cellular blue nevus. The lymph nodes showed massive invasion by pigmented cells and contained extensive necrotic foci. After 3.5 years of clinical follow-up, the patient is free from disease.<br> The absence of malignant features in the cutaneous lesion and the bland nuclear features of the pigmented cells in the regional lymph node metastases suggest that this case could be interpreted as an unusual form of benign cellular blue nevus with metastases. Nonetheless, other possibilities, such as malignant melanoma mimicking a cellular blue nevus or primary malignant melanoma of the lymph nodes with concomitant cutaneous cellular blue nevus, cannot be definitively excluded. A conservative surgical approach with close follow-up was recommended.