Malignant blue nevus: clinicopathologic study with AgNOR measurement. Seven cases

BACKGROUND: Malignant blue nevus is a very rare tumor. Argyrophilic nucleolar organizer regions (AgNORs) have been reported to be both a diagnostic and prognostic clue in various tumors, especially if standardized using an image analysis systems. PATIENTS AND METHODS: Seven cases of malignant blue nevus were retrospectively recorded between 1974 and 1999, and their clinical and pathological features described. Using an image analysis system, AgNOR measurements were studied in all cases. These results were compared with those obtained in 10 cases of commun blue nevus, 10 cases of cellular blue nevus and 10 cases of malignant melanoma. RESULTS: The most frequent location of malignant blue nevus was the scalp. Clinically, the tumor generally consisted of a blue nodule, 2.5 cm in diameter. There was no single histopathological criterion for the diagnosis of malignant blue nevus. AgNOR measurement was significantly higher in malignant blue nevus in comparison with commun blue nevus (p<0.0004) or cellular blue nevus (p<0.012), whereas there was no difference between malignant blue naevus and malignant melanoma (p > 0.50). DISCUSSION: Our results confirm the severe prognosis of malignant blue nevus and highlight the necessity of removing all blue tumours located on the scalp. AgNOR measurement using an image analysis system appears to be a useful tool for the diagnosis of malignant blue nevus, but further studies remain necessary.