Benign and malignant cellular blue nevus. A clinicopathological study of 30 cases.

The clinical and pathological features of 29 cellular blue nevi (CBN) and one malignant cellular blue nevus from our hospital files were reviewed. Although the sacrococcygeal region/buttock was the commonest single site, the majority of CBN occurred on the limb peripheries. Two-thirds of patients were under the age of 40 years. Follow-up of a mean of 7 years did not reveal any evidence of malignancy. Four histological subtypes were recognized: mixed biphasic, alveolar, fascicular or neuronevoid, and atypical varieties. One case developed a benign nodal metastasis. In one case, malignancy arose within a CBN. The importance of recognizing the variety of patterns, the benign behavior of the atypical variety, and the criteria for malignancy are herein discussed.