[Malignant transformation of an eccrine spiradenoma].

INTRODUCTION: Malignant eccrine spiradenoma is a rare and aggressive tumor, developed on the epithelium of eccrine sweat glands. Typically, it occurs after malignant transformation of benign eccrine spiradenoma, but sometimes it happens de novo.

OBSERVATION: We report a case of malignant eccrine spiradenoma in a 62-year-old woman. The patient presented a rapid increase in size of a long-standing tumoral lesion of her forearm. There was no secondary lesion on the chest, abdomen or pelvis at the CT-scanner. Cutaneous biopsy of the lesion was performed and showed a carcinoma with no contact with epidermis. On this biopsy, we could not affirm if the tumor was a metastatic process or a primary tumor of the skin. Histologic examination of the surgical removal of the tumor showed an undifferentiated carcinoma with adjacent nodules of eccrine spiradenoma. Immunohistochemical assessment of Ki67 expression showed a weak expression (5%) in the benign spiradenoma nodules and a high rate expression (80%) in the malignant neoplasm. The final diagnosis was an undifferentiated carcinoma arising from preexisting benign spiradenoma.

DISCUSSION: Malignant eccrine spiradenoma is not frequent and is rarely described in the international literature that may lead to diagnostic difficulties.