2021 Volume 36 Issue 1 Pages 86-89
A 42-year-old woman underwent left-sided breast cancer resection and sentinel lymph node biopsy. The fibrous capsule of the lymph node contained a cluster of cells with homogeneous round-to-oval nuclei and sporangia containing abundant brown granules. Tumor cells were also present in the lumen of the adjacent lymph vessels. Although the tumor cells did not exhibit any abnormal mitotic images, there was a large number of tumor cells, and it was difficult to determine whether the tumor was benign or malignant. Immunostaining revealed S-100 positivity, Melan A positivity, HMB-45 minority positivity, PRAME negativity, and consistent 5-hmc expression. Resultantly, the patient was diagnosed with nevus cell aggregates in the lymph nodes. Although the presence of benign nevus cells in the lymph nodes is rare, it is important to differentiate this from malignant melanoma metastasis. However, it is difficult to establish a diagnosis based on the morphology and arrangement of the tumor, and caution is required. In the present case, we were able to confirm the diagnosis based on PRAME and 5-hmc staining.[Skin Cancer (Japan) 2021 ; 36 : 86-89]
