Diagnosis:  C. Melanoma with balloon cell change

Histology: The skin resection shows an epidermal and dermal based lesion of epithelioid cells with prominent nucleoli and irregular nuclear contours. A subset of the cells shows prominent pale, foamy, and histiocytoid cytoplasm.

Discussion: This is a nice example of a malignant melanoma with balloon cell change. On clinical exam or on gross exam, melanomas with balloon cell change do not look any different than melanomas with other growth patterns, and there is no clinical or prognostic significance to the balloon cell change. In melanomas with balloon cell change, the malignant melanoma cells display expanded, granular cytoplasm that looks like the cell “ballooned” out, and there are adjacent or admixed other conventional appearing malignant melanocytes. The cells with balloon cell change resemble the cells in benign “balloon cell nevi,” but the malignant melanomas also show atypia and mitoses. The histologic differential diagnosis of the cells with balloon cell change includes other clear cell lesions: histiocytic neoplasms, histiocytic chronic inflammation, sebaceous neoplasms, lipoma or adipocyte tumors, metastatic renal cell carcinoma, clear cell syringoma or other. The presence of the classic-type malignant melanoma cells confirms the diagnosis. If needed, particularly on the limited material of a biopsy, immunostains for melanocytic markers such as S100, HMB45, Melan A or Sox10 can confirm the melanocytic differentiation of the lesion.

References
1. Kao GF, Helwig EB, Graham JH. Balloon cell malignant melanoma of the skin. A clinicopathologic study of 34 cases with histochemical, immunohistochemical, and ultrastructural observations. Cancer. 1992 Jun 15;69(12):2942-52.