It's more than you know

With a quick investigation via pubmed.gov, it only takes a few moments to make a clear determination that ‘eccrine carcinoma’ is a highly disorganized affair. Several hundred citations remain after exclusion of porocarcinoma, and those manuscripts include irreconcilable, conflicting statements that have a Tower of Babel quality. For example, Idrissi Serhrouchni et al1 aver ‘‘eccrine carcinoma is an extremely rare malignancy of the skin with few well documented cases reported in the literature. It is frequently found on the lower extremities,’’ while Falkenstern-Ge et al2 claim ‘‘Sweat gland [eccrine] carcinoma is a rare malignancy with a high metastatic potential seen more commonly in elderly patients. The scalp is the most common site of occurrence. ’’ The microscopic illustrations associated with these two manuscripts demonstrate very different and poorly differentiated epithelial malignancies that are not recognizable as exhibiting specific histomorphology. These two manuscripts illustrate much of what is wrong with ‘eccrine carcinoma’. A rare malignancy that has been rigorously, precisely, narrowly, and properly defined is unlikely to be simultaneously predominant to the scalp and predominant to the leg. Its histopathologic attributes should be readily recognizable to the experienced eye. When it comes to ‘eccrine carcinoma’, there is probably more fiction than fact. [As an independent observation, Idrissi Serhrouchni et al1 do not resolve how an ‘‘extremely rare malignancy’’ could be ‘‘frequently found’’ at any site, but that can remain as an additional mystery on the matter. ] Since bandying about the designation ‘eccrine carcinoma’ represents deploying a term that has not been rigorously, precisely, narrowly, and properly defined, it is perhaps unsurprising that use of the diagnosis can create confusion. A couple of summers ago, a patient contacted me emergently because they had received a diagnosis of ‘eccrine carcinoma’ from a medical center in the Northwest and had investigated their prognosis via google.com and decided things did not look good. The patient was desperately seeking an oncologist or surgical oncologist who specialized in ‘eccrine carcinoma’ and was hoping to receive insider advice on the matter. We were unable to match the patient with an ‘eccrine carcinoma’ specialist (a rare beast in the medical kingdom), but review of the slides from the case revealed it to be a low-grade form of adnexal carcinoma with ductal differentiation. As that diagnosis turned out to be much less correlated with harsh Internet content, it tended to deflate the patient’s panic. Organizing the published heterogeneity that represents ‘eccrine carcinoma’ in any meaningful way would be a formidable challenge at best, and improving the situation by ‘unpublishing’ past misleading content is clearly impossible. What, then, can be done? A three-step program is discussed briefly in the sections that follow. Step 1: recognize that use of the adjective ‘eccrine’ is almost always more than one knows. It is not provable that a given duct is an indicator of eccrine differentiation. Stop utilizing ‘eccrine’ as a synonym for ductal. If the diagnosis is ‘carcinoma with ductal differentiation’, say that. We as microscopists are adroit at identifying various microscopic minutiae, including structures or qualities such as caterpillar bodies, cytoplasmic granularity, or ‘dots’ of immunopositivity (in the context of Merkel cell carcinoma). We are also adept at recognizing ductal differentiation, which is typically manifest as small spaces lined by a compact eosinophilic cuticle. However, there is no means to read the mind of a duct and determine if it is eccrine, apocrine, sebaceous, or non-adnexal in nature.3,4 The recognition of ducts is easy (for the trained eye), but determining the true nature of such ducts is impossible. Step 2: since eccrine differentiation cannot be proved, histopathologically, the designation ‘eccrine’ should not be included in tumor names. New tumor names including ‘eccrine’ as a component should be abandoned until unequivocal authentication of ‘eccrinicity’ can be established. This includes designations such as ‘squamoid eccrine ductal carcinoma’. The