Eccrine poromas are the most common tumors in the poroma family of skin tumors. Other tumors in this family include the dermal ductal tumor, the poroid hidradenoma, and the hidroacanthoma. Eccrine porocarcinoma is the rare malignant counterpart to the eccrine poroma. Eccrine poromas develop from the appendageal structure sof the skin. Theall-encompassing term poroma is more accurate in that it appears that not all of these tumors are derived from eccrine structures. There is unconfirmed evidence that the cell of origin is actually apocrine. Other possibilities for the cell of origin include the sebaceous gland and the follicular epithelium.
Clinical Findings: Eccrine poromas are uncommon tumors of the skin. They occur equally in men and women and almost exclusively in the adult population. They are typically small tumors, ranging from 5 to 20 mm. They are most frequently found on the soles and palms. As many as 50% to 60% of these tumors have been found on the sole, but they have been described to occur in any skin location. Pain and bleeding are the two most common symptoms encountered. Eccrine poromas tend to have a vascular appearance and often manifest as a red or purplish papule or nodule. They are almost always solitary in nature, and they easily bleed when traumatized. On inspection, the eccrine poroma often has a slight, dell-like depression surrounding the tumor. This is more commonly seen on acral skin. This dell, when seen by the perceptive clinician, often leads to a differential diagnosis that includes an eccrine poroma. There is nothing clinically that can be used with certainty to make the diagnosis. The differential diagnosis includes vascular tumors, metastatic lesions (particularly the vascular renal cell carcinoma metastasis), pyogenic granuloma, and melanoma, because some eccrine poromas exhibit pigmentation. The diagnosis is made by histological examination after biopsy.
Histology: Eccrine poromas show varying degrees of ductal differentiation. The tumor is well circumscribed and has characteristic features. The keratinocytes have been described as cuboidal. They tend to be small and have an increased nuclear to cytoplasmic volume. Necrosis is often seen in parts of the tumor. The ductal portions of the tumor are lined by an eosinophilic layer or cuticle. The stromal portions of the tumor are rich in vascular components. This vascular element imparts the red appearance to the tumor. Eccrine poromas can be histologically classified as other members of the poroma family of tumors, based on their location in the skin. As an example, the hidroacanthoma, a member of this family, is defined as an eccrine poroma that is entirely located in the epidermis.
The eccrine porocarcinoma is very uncommon; histologically, it is a tumor that is poorly circumscribed and often found in conjunction with an eccrine poroma. Cells with multiple large nuclei and multiple mitoses help make the diagnosis. Eccrine porocarcinomas can mimic metastatic adenocarcinomas, and immunohistochemical staining is required to make certain of the diagnosis.
Treatment: Although they are benign tumors, eccrine poromas often are located on the sole or palm and require removal from a functional standpoint. Surgical excision with a small (1-2 mm), conservative margin is curative. The recurrence rate is very low after surgical excision. Electrodesiccation and curettage has been used successfully. Eccrine porocarcinomas require surgical excision and close clinical follow-up. Chemotherapy is reserved for cases of metastatic disease. The role of sentinel lymph node sampling in these tumors has yet to be defined.