Cellular blue nevus (CBN) was established as a distinct entity by Allen and Spitz, (44) Allen, (45) and Rodriguez and Ackerman.
The term atypical cellular blue nevus has been applied to rare CBNs that show atypical histologic features and raise histologic differential diagnosis of malignant blue nevus.
Immunohistochemistry has been used in histologic differential diagnosis between cellular blue nevus, atypical cellular blue nevus, and malignant melanoma.
Key histologic features helpful in differentiating between cellular blue nevus, atypical cellular blue nevus, malignant blue nevus, and PEM are summarized in the Table.
Cellular blue nevus simulating metastatic melanoma: report of an unusually large lesion associated with nevus-cell aggregates in regional lymph nodes.