Spiradenoma With Marked Adenomyoepitheliomatous Features

Abstract

To the Editors: In 2008, we reported a series of 5 cases of spiradenoma and 1 case of spiradenocylindroma that, in addition to areas of a conventional growth, manifested an adenomatous component consisting of compactly situated well-developed glands having small round lumens lined by inner pale to eosinophilic cells and surrounded by an outer well-formed peripheral layer of myoepithelial cells.1 Lymphocytes, an essential constituent of a spiradenoma, were markedly diminished or absent in the adenomatous areas. In 4 of those 6 cases, the adenomatous component was a minor but significant portion of the tumors, but in 2 cases, it was quite prominent, comprising approximately 20% of the tumor area.1 We have recently encountered a case of spiradenoma in a 60-year-old male patient located on the right temple with an unduly marked adenomatous (adenomyoepitheliomatous) moiety, which clearly dominated over the conventional portion of the neoplasm, comprising in as much as 75% (Fig. 1A, B). As in the original neoplasms, each glandular structure was surrounded by a well-developed peripheral layer of myoepithelial cells, which stained for S-100 protein and alpha smooth muscle actin (Fig. 1C, D). These areas and myoepithelial differentiation were so prominent that one can speak of “adenomyoepitheliomatous” areas instead of a mere “adenomatous” component. The adenomyoepitheliomatous areas were identical to those seen in adenomyoepitheliomas in various organs. Apart from the prominence of the adenomyoepitheliomatous compartment, the present case manifested some other features that were neither observed in our previous report nor in that of Michal2 who described the first occurrence of well-developed glands in spiradenoma. Namely, albeit usually being simple with round lumina, some glandular structures in the present case manifested a more complex appearance, with intraluminal bridging or, occasionally, cribriform features (Fig. 1E, F). Additionally, there were multiple foci with squamous metaplasia and intraglandular clear cell metaplasia (Fig. 1G), and in some areas, it was evident that the squamous metaplastic epithelium is closely associated with the glandular elements.FIGURE 1: Spiradenoma (A) with a prominent and dominant adenomyoepitheliomatous component highlighted by alpha smooth muscle actin (B); glands with a well-developed peripheral myoepithelial cell layers adjacent to conventional areas of spiradenoma (C); peripheral myoepithelial cell layers highlighted by alpha smooth muscle actin (D); occasional glands demonstrating intraluminal bridging (E) and a cribriform appearance (F); and areas with squamous metaplasia. G, Clear cell change within some lumina.This case with unduly prominent adenomyoepitheliomatous differentiation further underscores diagnostic difficulties that may be caused by an unusual example of spiradenoma. It was sent in consultation with differential diagnostic considerations that included, among others, malignant transformation. Indeed, some malignant tumors arising within preexisting spiradenoma may manifest similar adenomatous areas, including adenocarcinoma in situ or invasive adenocarcinoma.3 In our original series on spiradenomas with an adenomatous component, there was one case with clearly atypical adenomatous component, which together with subsequent observations of invasive adenocarcinoma arising from benign spiradenoma suggests that one of the pathways of malignant transformation in spiradenomas may be via a sequence of adenomatous and atypical adenomatous change, adenocarcinoma in situ, and, ultimately, invasive adenocarcinoma.3 Denisa Kacerovska, MD, PhD Dmitry V. Kazakov, MD, PhD Sikl's Department of Pathology, Medical Faculty Hospital, Charles University, Pilsen, Czech Republic Heinz Kutzner, MD, PhD Dermatohistopathologische Gemeinschaftspraxis, Friedrichshafen, Germany Michal Michal, MD Sikl's Department of Pathology, Medical Faculty Hospital, Charles University, Pilsen, Czech Republic, Bioptical Laboratory, Pilsen, Czech Republic