Mammary-type Tubulolobular Carcinoma of Anogenital Mammary-like Glands With Prominent Stromal Elastosis

Abstract

To the Editor: Following the original description of mammary type tubulolobular carcinoma of the anogenital area, presumably originating in anogenital mammary-like glands (AGMLG) in 2006,7 we have recently observed a similar case. The neoplasm in this newly encountered case fulfilled the criteria for a tubulolobular carcinoma as defined in mammary pathology,5 and was almost identical to the original cutaneous example.7 Additionally, there was prominent stromal elastosis, a feature identical to that seen in association with invasive breast carcinomas, and not earlier recognized in carcinomas of the anogenital area. The patient was a 45-year-old female who presented with a 2-cm, asymptomatic solitary nodule in the vulva with unknown duration. Clinical investigation revealed no extracutaneous involvement; specifically, there was no mammary tumor. An enlarged lymph node in the right inguinal area was noted, but it proved negative on sentinel node biopsy, as did 2 other lymph nodes from the same region, and 3 left inguinal lymph nodes removed during a lymphadenectomy. After a wide surgical excision (specimen 4×2×1.2 cm), the patient is alive without signs of metastasis or recurrence at 4-year follow-up. Histopathologically, the tumor was composed of uniform round-to-ovoid cells arranged in a single-file pattern intermixed with areas manifesting round tubules often showing decapitation secretion at the luminal border. The neoplastic elements were arranged in a targetoid fashion or grew diffusely. The tubules were mainly composed of a single-cell layer without any evidence of a peripheral myoepithelial cell layer. Rare small solid aggregations were also noted. There were areas with perineural and intraneural invasion, especially in the foci, in which the tumor areas resembled an infiltrative lobular carcinoma (Figs. 1A–D). Immunohistochemically, the tumor cells in both ductal-like and lobular-like components reacted positively for E-cadherin. A remarkable feature was the prominent stromal elastosis emerging as clumps and masses of elastic material around individual neoplastic tubules (periductal elastosis) within the stroma (diffuse elastosis) and in association of vessel walls (vascular elastosis) highlighted by elastic stains (Fig. 1E, F). The residua of intact AGMLG were not recognized.FIGURE 1.: An infiltrative neoplasm in the dermis (A) containing areas with tubular formation and areas resembling infiltrative lobular carcinoma of the breast; areas of periductal, diffuse, and vascular elastosis can be discerned (B–D). Stromal elastosis is highlighted by elastic stains (E, F).In the breast, tubulolobular carcinoma was originally described as a tubular variant of lobular carcinoma,5 but many investigators nowadays regard neoplasm as a variant of invasive ductal carcinoma with a lobular growth pattern.2,12 There was only 1 earlier report of this tumor type in the skin.7 The neoplasm was suggested to originate from AGMLG, a normal constituent of the anogenital area, earlier considered to represent ectopic breast tissue.14 Lesions of AGMLG show a striking microscopic resemblance to their mammary counterparts.15 A majority of these lesions are epithelial or biphasic stromal epithelial neoplasms, including fibroadenoma and phyllodes tumors.8,9,10 Stromal changes in lesions of AGMLG seem to be also identical to those seen in their mammary counterparts. The most prominent stromal lesion is probably pseudoangiomatous stromal hyperplasia recognized in the anogenital area in 2005.6 In this case study, stromal elastosis seemed identical to that seen in mammary carcinomas. This feature is unusual for dermatopathologic cases. The prototype of the changes in the elastic tissue compartment, sometimes associated with cutaneous neoplasms, is a solar elastosis attributed to the degradation of collagen or elastic fibers owing to excessive sun exposure. Stromal elastosis in mammary carcinoma is an entirely different pathologic process characterized by the presence of excess elastic fibers in a diffuse manner within the stroma in the periductal location or around blood vessels. It is usually seen in invasive mammary carcinomas, especially ductal carcinomas but has been rarely found in benign lesions3 or even intact breast, wherein it is less prominent.4 Infiltrating neoplastic cells, when invading the basal lamina of the mammary ducts, are thought to stimulate periductal fibroblasts or myofibroblasts to produce elastic fibers.1,11,13 In normal circumstances, these cells are not engaged in elastic fibers production. Grossly, such stromal elastosis can be recognized as “chalky streaks.”1 This case of tubulolobular carcinoma of the vulva further highlights similarities between lesions of AGMLG and their mammary counterparts, including “secondary” stromal phenomena. Stromal elastosis is not a feature in invasive carcinomas of the skin, regardless of the histopathologic type. The likely explanation is that the stroma of AGMLG is physiologically different from the dermis and reacts to various stimuli in a manner similar to the mammary stroma. Maria Teresa Fernandez-Figueras, MD* Michal Michal, MD† Dmitry V. Kazakov, MD, PhD† *Department of Pathology Hospital Universitari Germans Trias i Pujol, Autonomous University of Barcelona Barcelona, Spain †Sikl's Department of Pathology Charles University Medical Faculty Hospital Pilsen, Czech Republic