There is a background lesion compatible with an eccrine poroma. However, there is supervening high grade epithelial cell atypia and as well the lesion exhibits an irregular growth pattern within the corium. In regards to the latter individual cells and small nests of severely atypical cells assuming an infiltrative growth pattern amidst a hypervascular stroma. The lesion is best treated and categorized as an excellent prognosis well differentiated porocarcinoma.
Eccrine porocarcinoma is a rare malignant sweat gland tumor that tends to arise on the lower limbs, trunk or head and neck region, can range in size from <1 cm to 10 cm and assume a nodular or infiltrative growth pattern. Clinically, these tumors may be mistaken for a seborrheic keratosis, basal cell carcinoma, squamous cell carcinoma, pyogenic granuloma and even an amelanotic melanoma. While uncommon, regional lymph node metastases as well as distant metastases have been reported in 20% and 10% of cases, respectively.
Murilo de Almeida Luz et al. Eccrine Porocarcinoma (Malignant Eccrine Poroma): A Series of Eight Challenging Cases. Clinics (Sao Paulo). 2010 Jul; 65(7): 739-742.