Spiradenocylindrocarcinoma: a malignant hybrid tumor.

Background:  Eccrine spiradenomas and cylindromas are benign, slowly growing, cutaneous adnexal neoplasms, recently hypothesized to arise from a common pluripotential cell; malignant variants are rare. We found 48 cases of malignant spiradenomas and 33 cases of malignant cylindromas reported in the English literature. Benign tumors demonstrating both spiradenomatous and cylindromatous features have been infrequently reported. Recent immunohistochemical studies of these two tumors have provided compelling evidence that these two tumors may merely represent a single tumor type with a spectrum of histological features. Case report:  We describe two cases of a malignant variant of this rare hybrid tumor occurring in a 62-year-old male and a 72-year-old female. Conclusion:  We propose the term ‘spiradenocylindrocarcinoma’ to describe malignant tumors with features of both a spiradenoma and a cylindroma. In conjunction with histological features of malignancy, p53 and Ki-67 immunohistochemical staining may provide helpful clues in determining the malignant potential of this tumor. Further studies are needed to clarify the biologic behavior of such lesions.