Microglandular Adenosis 73 Figure 1. Ultrasonographic finding of microglandular adenosis. Ill-de- fined low echoic lesion (BIRADS category 5) in the upper outer quad- rant of right breast was shown in ultrasonogram. Figure 3. Microscopic finding of microglandular adenosis (MGA). Infil- trating round glands lacking a myoepithelial layer are seen with luminal eosinophilic secrestions. The glands are regular and small, and are lined by single epithelial layer (H&E stain, × 40). Figure 2. Gross appearance of microglandular adenosis (MGA). This is a gross appearance of MGA. Hematoma in the mass is result of the previous needle biopsy. are women, ranging in age from 28 to 82 years. Most patients complain of a palpable breast mass or breast thickening that may arouse a clinical suspicion of carcinoma. MGA can also be found incidentally [2]. It is often 3 to 4 cm in size, but oc- casionally the lesion can be greater than 20 cm, and the mar- gin is usually ill-defined or infiltrative [2]. Mammographic findings of MGA may show increased density or calcifications stimulating breast cancer and lead to a core needle biopsy. Histologically, MGA is characterized by a haphazard infiltra- tion of small, uniformly open, and round glands in dense, hy- pocellular, and fibrous tissue, or fatty mammary stroma [3,4]. The glands are lined by a monolayer of flat to cuboidal epithe- lial cells that lack a myoepithelial layer (Figure 3) [2], which can be verified by immunohistochemistry. MGA immunohis- tochemistry is positive for pancytokeratin and negative for smooth muscle actin (Figures 5, 6), so the lesion is often con- DOI: 10.4048/jbc.2011.14.1.72 Figure 4. Immunohistochemistry (IHC) of microglandular adenosis (MGA). IHC of MGA shows positive for S-100 protein (IHC stain, × 40). fused with a tubular carcinoma. The absence of stromal des- moplasia and the presence of a thickened basement membrane help distinguish MGA from carcinoma [5,6]. MGA has no lob- ular grouping and frequently overruns normal elements, but it does not invade the perineurium or vasculature. Epithelial cells often lack apical snouts and have vacuolated or clear cy- toplasm that contains glycogen [2,7]. The lumens of the glands contain clear or eosinophilic colloid-like secretions, usually positive for PAS and mucicarmine, and occasionally luminal calcification [5,8]. The glands are completely invested by a base- ment membrane that can be highlighted by type IV collagen, laminin, or PAS staining [7,9]. MGA has no myoepithelial cells, and the epithelial cells are usually positive for cytokeratin and S-100 protein (Figures 4, 5). The epithelial cells are also posi- tive for CAM 5.2, AE-1, and cathepsin D. but negative for es- trogen receptor (ER), progesterone receptor (PR), and human http://ejbc.kr