By Robert M. Law, M.D.
The subdivision of adnexal neoplasms is one of the most complicated areas of Dermatopathology. Classification of these tumors is wrought with homonyms, and heterologous tumors often defy definitive nomenclature. An additional dilemma arises when the histologic picture overlaps with metastatic carcinoma, particularly breast primaries. Both may manifest with a densely sclerotic stroma with entrapped epithelial cords and duct epithelium. Perineural invasion is a consistent finding in eccrine carcinomas, but may also be seen in infiltrating carcinoma of the breast.
In our consultative practice, we were recently presented with a tumor in the axilla of a man in his thirties. The histology was that of a sclerosing ductal neoplasm, as seen in Figure 1. Given its anatomic location, the possibility of a primary breast carcinoma was raised. Figure 2 displays an example of an infiltrating ductal carcinoma of the breast, taken from our archival material at PROPATH. The histologic similarities are vexing, and a definitive answer often requires the use of ancillary studies.
As is commonly the case, a battery of immunohistochemical stains is required to delineate the origin of these tumors. Cytokeratin markers, myoepithelial markers, growth factor and hormonal receptors are all used, and the results will often point us to the culprit. Table 1 summarizes findings typical of both primary sclerosing adnexal carcinoma and selected metastatic lesions.
In our example (Figure 3), strong staining for Cytokeratins 5/6, and positivity for both D2-40 and p63 favored a primary sclerosing eccrine carcinoma, rather than a breast primary. Clearly, subsequent therapy would have differed significantly, making definitive subclassification paramount.
Sclerosing eccrine carcinoma is known by many different names, including microcystic adnexal carcinoma, malignant syringoma, and sclerosing sweat duct carcinoma. This tumor was first described by Goldstein, Barr, and Santa Cruz in 1982. Typically located on the face, other reported locations include the axilla, extremities, and genital skin. It is a slow-growing, but locally aggressive tumor that affects adults, with a 50% recurrence rate. Although a single metastasis to a lymph node has been reported, this most certainly represented contiguous growth, rather than true metastasis.
Acknowledgments: Special thanks to Dr. Brad Graham of Dermatology Associates of Tyler for contributing this most interesting case.
1. Goldstein DJ, Barr RJ, Santa Cruz DJ. Microcystic adnexal carcinoma. A distinct clinicopathologic entity. Cancer 1982; 50:566-572
2. Qureshi HS et al. The diagnostic utility of p63, CK5/6, CK 7 and CK 20 in distinguishing primary cutaneous adnexal neoplasms from metastatic carcinomas. Journal of Cutaneous Pathology 2004: 31:145-152.
3. Liang H et al: D2-40 is highly expressed in primary skin adnexal carcinomas but negative in adenocarcinoma metastases to skin. Modern Pathology 18(supplement 1): 86A (abstract # 386), January 2005.