Cutaneous neoplasms showing differentiation toward the sweat gland units are relatively uncommon specimens in general pathology but are not so uncommon in dermatopathology. Despite that fact, their histologic diversity—and the plethora of nosologic schemes that have been applied to them in the past—can be daunting at first glance. In this specific context, one is faced with a decision to adopt a stance of terminologic minimalism, using such diagnostic terms as “benign sweat gland neoplasm,” or to embrace more eclectic nomenclature as applied to adnexal tumors. This chapter (and Chap. 28) presents a moderate stance in reference to the latter issue, using a classification system that is attuned as much as possible to concepts and terms that are commonly embraced in surgical pathology and to the latest WHO classification. Because of the relatively nondescript clinical features attending many sweat gland tumors, these are not covered in any detail except for lesions in which they are distinctive and contribute meaningfully to pathologic diagnosis.
The topic of cutaneous adnexal neoplasia is a broad and complicated one; indeed, several entire textbooks have been devoted to it.1-4 Hence, the following material is intended to present a practical, diagnostically directed synopsis rather than an encyclopedic treatment of the subject, and interested readers are referred to the reference sources previously cited for additional information (see General Considerations, Chap. 28).
IMMUNOHISTOCHEMISTRY OF SWEAT GLAND TUMORS
Immunohistology does have some application in the differential diagnosis of sweat gland neoplasms, as referenced at several points in this chapter. However, this technique must be applied very specifically to tightly confined questions of interpretation because the immunophenotypes of sudoriferous tumors overlap with each other and—in the case of sweat gland carcinomas—with the antigenic profiles of visceral malignancies.1-4 Hence, the greatest utility of immunostains in this context is in the separation of sweat gland tumors from other primary skin lesions, such as variants of squamous cell carcinoma, basal cell carcinoma (BCC), melanoma, and mesenchymal neoplasms with epithelioid cytologic features. Table 29-1 outlines the determinants of interest and expected reactivity patterns. Detailed immunophenotypes of specific sweat gland tumors are provided in the respective sections for each entity.
Table 29-1Immunohistochemical Findings in Sweat Gland Tumors and Differential Diagnostic Alternatives |Favorite Table|Download (.pdf) Table 29-1 Immunohistochemical Findings in Sweat Gland Tumors and Differential Diagnostic Alternatives
|TUMOR ||PANCK ||EMA ||CK7 ||CK20 ||CEA ||S100 ||AR ||GCDFP15 ||P63 ||GATA3 ||CK5/6 |
|Benign and malignant eccrine neoplasms ||+ ||+ ||+ ||0 ||± ||± ||0 ||± ||+a ||± ||+a |
|Benign and malignant apocrine neoplasms ||+ ||+ ||+ ||0 ||± ||± ||± ||+ ||+a ||± ||+a |
|EPD and MPD ||+ ||+ ||+ ||Rare ||+ ||0 ||± ||± ||+a ||+ ||+a |
|Metastatic visceral carcinoma ||+ ||± ||± ||± ||± ||± ||± ||± ||0a ||± ||0a |
|Melanoma ||0 ||0...|