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SUMMARY
Sweat gland neoplasms are loosely organized into apocrine tumors and eccrine tumors.
As a whole, these are relatively unusual tumors, but benign adnexal neoplasms will most certainly be encountered in clinical practice.
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DON’T FORGET
The differential diagnosis for suspected adnexal neoplasm must always include metastatic adenocarcinoma.
Histologically, adnexal neoplasms can be difficult to differentiate from basal cell carcinoma and squamous cell carcinoma, but it is critically important to do so as they may show more aggressive clinical behavior.
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CLINICAL PEARLS
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PATIENT EDUCATION POINTS
Although adnexal neoplasms are generally not considered “premalignant,” there have been reported cases of benign adnexal neoplasms transforming into malignant neoplasms. Thus, patients should be counseled to monitor previously biopsied tumors for any growth or change.
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Sweat gland tumors have been historically divided into those with eccrine and apocrine features. Most of these tumors are named based on their degree of resemblance to normal constituents of the eccrine and apocrine glands and ducts. It is helpful to organize these tumors by degree of differentiation toward eccrine or apocrine sweat glands rather than stating categorically that a tumor arose from a specific part of the sweat gland.1 The morphologic similarities between the intradermal portions of the eccrine and apocrine duct lead to difficulties in segregating tumors with ductal differentiation into definite categories of “apocrine” and “eccrine” tumors. Markers of apocrine differentiation include histologic identification of columnar cells with decapitation secretion and identification of lysosomal enzymes, including acid phosphatase and B-glucuronidase.2 A definite immunohistochemical marker of eccrine or apocrine differentiation does not currently exist. The eccrine and apocrine neoplasms are primarily intradermal neoplasms. For this reason, punch biopsy or excisional biopsy is recommended. The differential diagnosis may include a primary adnexal carcinoma or metastatic adenocarcinoma. In these cases, architectural features are of paramount importance and may only be observed in an adequate biopsy specimen. In cases of benign adnexal neoplasms with an adequate biopsy that samples the entire lesion, further surgery or therapy may not be necessary.
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Tumors with eccrine and apocrine sweat gland differentiation are relatively unusual. Benign tumors of the sweat glands, though uncommon, may be seen in clinical practice. In a review of over 100,000 cases from a private dermatopathology laboratory, eccrine poroma, syringoma, and hidrocystoma represented three of the more common glandular tumors representing approximately 0.4% of all specimens received. Eccrine spiradenoma, syringocystadenoma papilliferum, hidradenoma, and cylindroma represent less common benign sweat gland tumors, making up less than 0.1% of all specimens received. Malignant neoplasms with eccrine and apocrine differentiation are relatively rare and represent approximately two to three specimens per 100,000 received. Although relatively rare, it is important to recognize benign sweat gland tumors to avoid confusion with basal ...