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Eccrine cancers are uncommon, but potentially recurrent, metastatic and fatal. Rarely, they are primary foot lesions. The literature records 46 foot cases, with age and sex given for 41. Various eccrine cancer types (most on the sole), affected all races, males predominating. Average age at diagnosis was approximately 55. A podiatric facility recorded eight cases among approximately 30,000 skin biopsies, during 15 years. Seven arose in women. Five arose in the great toe area. Three are porocarcinomas. Five are "adenocarcinomas" varying in degree of differentiation. None of the eight patients presented recurrence or metastasis during follow-up 0.5-13.4 years. Of the combined 49 literature and podiatric cases, 28 (57.1%) arose in men, mostly between ages 41 and 70. Most were slow growing, long standing, and mildly symptomatic. No clinical features distinguished eccrine cancers from other pedal tumors.

Eccrine porocarcinoma, a malignancy of the eccrine sweat glands, is extremely rare. Our report and a review of the literature (70 cases) emphasize the features of this tumor. Age at time of treatment ranged from 19 to 94 years (mean 67 years). Duration of the lesion ranged from two months to 50 years; 31 (44%) had the lesion present > or = 5 years. Forty-four patients (62%) had tumors located on the extremities, 13 (19%) on the head and neck region and 12 (17%) on the trunk. All patients whose race is known were white. Primary treatment should consist of wide local excision and regional lymphadenectomy, if clinically indicated. Although there is a significant risk of cutaneous, regional lymph node, or visceral metastases, the value of elective or therapeutic regional lymphadenectomy is unknown, as is the role of adjunctive therapy.

A single poroid neoplasm composed of three histologically distinct lesions (hidroacanthomas simplex, eccrine poroma, and dermal duct tumor) is reported. Comparative histologic, histochemical, and electron-microscopic studies revealed that each tumor subtype contained varying proportions of poroid cells, clear cells, and cuticular cells. The major component of all three neoplasms was poroid cells, which, under the electron microscope, were characterized by a few, small, poorly developed desmosomes, and were histochemically characterized by a positive succinic dehydrogenase reaction. The dermal duct tumor was cultured, and showed similar histochemical findings to the in vivo poroid cells. These results suggest that poroid cells play the most important role in the histogenesis of these three neoplasms.

Eight cases of malignant eccrine poromas were studied immunohistochemically with a broad panel of antibodies in order to better characterise the spectrum of their differentiating pathways. Special attention was paid to the expression of cytokeratins, mainly the newly recognised keratin 20. In general, the pattern of staining agreed to previous studies. Anyway, a non-expected positivity with keratin 20 was seen in two cases. The usefulness of the immunohistochemistry to discover areas with masked differentiation in adnexal tumours of the skin was once more confirmed.

Squamous differentiation in poral adnexal neoplasms is a rare event. Two cases are presented of malignant eccrine poroma in which areas of squamous differentiation showing the features of squamous cell carcinoma were present. The areas of squamous differentiation were found within the invasive components of the lesions and appeared to result from direct transformation of the poral epithelial cells. A review of the literature on this unusual phenomenon is presented.

Thirty-one dermal appendage tumors of sweat gland differentiation including 7 spiradenomas (SPA), 8 cylindromas (CYL), 8 acrospiromas (ACS), and 8 chondroid syringomas (CS) were analyzed using antibodies to epithelial membrane antigen (EMA), cytokeratin (AE1, AE3, CAM 5.2, 34BE12), S-100 protein, actin (ACT), and desmin (DES) to characterize the immunocytochemical profile of benign sweat gland tumors. Cytokeratin expression was variable; AE1, 34BE12, AE3, and CAM 5.2 were present in 31, 24, 23, and 22 tumors respectively; 29 tumors contained EMA. Seventeen tumors, (6 SPA, 8 CYL, 2 ACS, 1 CS) stained with antibody to alpha smooth muscle actin, and 26 (7 SPA, 7 CYL, 4 ACS, 8 CS) expressed S-100 protein. Although some prior studies had reported actin filaments on electron microscopy in both spiradenoma and cylindroma, these tumors have previously been considered to be negative for myoepithelial differentiation. All spiradenomas and cylindromas we studied demonstrated actin and/or S-100 protein positivity in basal epithelial cells, consistent with myoepithelial differentiation. The organization of actin and S-100 protein positivity displayed by the spiradenomas and cylindromas we studied suggests that the tumors are differentiated towards the secretory portion of the eccrine sweat gland.