porocarcinoma, page1

ECCRINE POROCARCINOMA

From the abdominal skin of an elderly patient: About a year after this specimen was obtained, I was informed that this patient had metastatic carcinoma in groin lymph nodes, and the tumor had features compatible with the one depicted here. I have no further followup.

You can also find eccrine porocarcinoma (EP) described in various texts as malignant eccrine poroma and as malignant hidroacanthoma simplex. The diagnosis can be prefaced by in situ or intraepidermal when applicable. Some authors still use the intraepidermal epithelioma of Jadassohn and Borst (IEJB) term for the in situ stage, but it is doubtful that Jadassohn or Borst were describing this tumor. Furthermore, IEJB has been used erroneously for a variety of other lesions including clonal seborrheic keratoses.

The epidermal surface of EP is characteristically rough or somewhat verrucoid, and the lesion has the configuration of a plaque.

The cells forming the intraepidermal nests in EP are much more atypical than those found in hidroacanthoma simplex or in clonal seborrheic keratosis. There usually are transitional forms of the cells between the nests and the adjacent cells in clonal seborrheic keratoses. The cells in Bowen's disease and other forms of bowenoid atypia may form clusters and be confused with in situ EP. There usually is more evidence of transepidermal invlolvement in bowenoid atypia, but there are cases where the distinction is very difficult, and a diagnosis such as intraepidermal carcinoma, probably eccrine could be used when EP is suspected. The intraepidermal cells in EP are often positive for carcinomembryonic antigen.

Invasive EP is characterized by the presence of nests of cells resembling poorly differentiated squamous cell carcinoma. Intracytoplasmic lumen formation, which is very characteristic of eccrine tumors of skin, may be difficult to find, but the search is worthwhile. Actual neoplastic gland or duct formation is uncommon. These tumors have a propensity to metastasize (about 20%). There have been examples that extensively involved the lower extremeties and were designated as epidermotropic eccrine carcinoma.

Scan power view. Note the hyperkeratotic and somewhat verrucoid surface.

Low power view. There are sharply demarcated nests of tumor within the epidermis. There is sparing of a rim of normal epidermal keratinocytes in most areas.

High power view.There is much more atypia than would be expected in a clonal seborrheic keratosis or in hidroacanthoma simplex. There are no transitional atypical cells blending with the peripheral normal keratinocytes. An abnormal mitosis is seen in this picture.

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	Scan power view. Note the hyperkeratotic and somewhat verrucoid surface.
	Low power view. There are sharply demarcated nests of tumor within the epidermis. There is sparing of a rim of normal epidermal keratinocytes in most areas.
	High power view.There is much more atypia than would be expected in a clonal seborrheic keratosis or in hidroacanthoma simplex. There are no transitional atypical cells blending with the peripheral normal keratinocytes. An abnormal mitosis is seen in this picture.