Eccrine porocarcinoma is an uncommon sweat gland malignancy. To the best of our knowledge, there has been no report in the English literature of porocarcinoma with predominantly undifferentiated sarcomatous change. We present two cases of sarcomatoid eccrine porocarcinoma associated with a benign poroma. Case 1 pertained to an 82-year-old woman with an ulcerated chest wall tumor, and Case 2 was that of a 74-year-old woman who presented with an ulcerated plaque in the lower leg. Case 1 showed an unusual pseudo-angiosarcomatous morphology with spindle cells dissecting through collagen bundles and forming vascular like channels. Case 2 revealed high-grade malignant spindle cells with focal evidence of ductal differentiation. In both the cases, benign poromatous elements were histologically evident. Immunohistochemistry performed showed pancytokeratin positivity in spindle cells of both lesions. Epithelial membrane antigen and carcino-embryonic antigen positivity in the malignant ductal elements and focal smooth muscle actin staining of the spindle cells were demonstrated in Case 2. A brief review of relevant literature is presented.

Eccrine porocarcinoma: a case with an obscure primary tumor diagnosed from lymph node metastasis.Am J Dermatopathol. 2007 Apr;29(2):176-9.

Eccrine porocarcinoma (EPC), a rare malignant epidermal appendage tumor, is mainly seen in elderly patients. A long history is one of its main characteristics. Two types of EPC are known: juxtaepidermal and dermal. The juxtaepidermal type usually has a more aggressive behavior. Lymph node metastasis and high mitotic activity are associated with poor prognosis. A case of EPC with a long-standing but indolent primary site diagnosed from lymph node metastasis is presented here. There was also accompanying chronic dermatitis as a paraneoplastic syndrome. Diagnosing EPC prior to the regional lymph node involvement is the most valuable factor for a successful treatment. Persistent examinations and attempts to find the primary site(s) have to be made in such cases.