Melanoma associated with blue nevus and melanoma mimicking cellular blue nevus - A clinicopathologic study of 10 cases on the spectrum of so-called 'malignant blue nevus'

The term "malignant blue nevus" refers to a ran and heterogeneous group of melanomas that arise in several clinical settings. This includes melanomas arising in association with a common or cellular blue nevus and those arisi ng de novo and resembling cellular blue nevi. We reviewed the clinicopathol ogic features of 10 cases of malignant blue nevi. Six cases proved to be de novo melanoma mimicking cellular blue nevus, but lacking a clear-cut benig n component. Two melanomas arose in association with a common blue nevus, a nd two with a cellular blue news. The patients' (5 males, 5 females) ages r anged from 11 to 77 years (average age, 48.1 years). The head and neck was the most common location (6 of 10 patients), with five scalp tumors. Four t umors were located on the trunk; none was located on the extremities. Tumor size ranged from 0.5 to 2.2 cm (average size, 1.1 cm). Most lesions had be en present for many years before surgical removal. Pigmented dendritic cell s were observed in 9 of 10 cases. The malignant and benign components were easily distinguished in the four cases that arose in association with a com mon or cellular blue nevus. Abrupt transition between a benign blue nevus a nd melanoma was readily recognized at scanning magnification as distinctive nodules of epithelioid to spindled cells with a sheet-like growth pattern. In dr cases, malignancy was evidenced by increased mitotic rate, necrosis, nuclear atypia, pleomorphism, hyperchromasia, and prominent nucleoli. All 7 patients with followup information experienced recurrence (3 patients) or metastasis (4 patients). Three patients died of disease. Malignant blue ne ws is a heterogeneous group of melanomas that are highly aggressive and oft en lethal, with a propensity for metastasis to the lymph nodes and lungs.