ECCRINE POROMA
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.
