Although the vast majority of
eccrine spiradenomas behave in a benign fashion, 23 cases of malignant transformation have been reported to date. We describe a unique example of malignant
eccrine spiradenoma that arose in the right breast of a 68-year-old woman. The quiescent mass, which was present for approximately 50 years, experienced sudden enlargement with erythematous changes of the overlying skin and nipple discharge. Microscopically, the
tumor showed the typical features of an
eccrine spiradenoma with areas of
adenocarcinoma,
squamous cell carcinoma, and
sarcoma. The sarcomatous component consisted of
rhabdomyosarcoma and
osteosarcoma. The immunoperoxidase staining revealed p53
protein expression only in the carcinomatous and sarcomatous components. This suggests that accumulation of p53
protein may be an important event in the malignant transformation of
spiradenomas. Because of its location and biphasic nature, this malignant
eccrine spiradenoma should be distinguished from metaplastic
breast carcinoma. To our knowledge, this represents the first carcinosarcomatous transformation of
eccrine spiradenoma in the breast. This case led us to conclude that breast tissue, which often undergoes apocrine
metaplasia and gives rise to apocrine
neoplasms, is also capable of originating benign and malignant
tumors with eccrine sweat duct phenotype.