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[152] Clinical, Histopathologic, and Biologic/Molecular Features of Microglandular Adenosis with Transition into In-Situ and Invasive Carcinoma

I Khalifeh, C Albarracin, Y Wu, N Sneige. M. D. Anderson Cancer Center, Houston, TX

Background: Microglandular adenosis (MGA) of the breast is a benign lesion that can mimic invasive carcinoma. Histologically, it is characterized by an infiltrative growth pattern and glands lacking a myoepithelial layer. Although carcinoma arising from MGA have been described, it is not clear which cases of MGA will progress to carcinoma, and criteria to distinguish MGA with atypia (AMGA) from MGA involved by carcinoma (MGACA) are lacking.
Design: To better define criteria for differentiating between MGA, AMGA, and MGACA, we evaluated morphologic and prognostic markers in cases of MGA with transition to carcinoma. We obtained 64 cases designated MGAin a search of the Pathology database (1983 to 2006). Only 10 of the 64 cases fulfilled morphologic and immunohistochemical (S-100+, SMA-) diagnostic criteria of MGA, AMGA, or MGACA. Cases were evaluated by immunohistochemistry for cell cycle markers (p53 and Ki-67) and markers for basal-like differentiation (ER, HER2, EGFR, C-kit, CK5/6, CK18, laminin, type IV collagen). Radiological features and clinical follow-up were evaluated.
Results: The 10 cases included six MGA and four AMGA with transition to MGACA. Mean patient ages were 60 y for MGA and 50 y for MGACA. Five of the six MGA cases were microscopic and were incidental and one case presented de novo as a palpable mass. None recurred at follow-up (119 y). Follow-up was available for three of four MGACA cases, one with disseminated disease died 2 years of diagnosis, and two had no recurrence within 2 years of diagnosis. All four cases with an invasive component showed transition from MGA to AMGA to invasive carcinoma. The carcinomatous component was metaplastic (one case), adenoid cystic (one case) and ductal carcinomas, NOS (two cases). All cases expressed S-100 and CK8/18, and did not express CK5/6, ER, PR, or HER2 and c-kit. EGFR was diffusely expressed in all six MGA cases and focally expressed in the four MGACA cases. Laminin was more intense in MGA cases and was attenuated in AMGA and MGACA. Ki-67 index was <1% in MGA, readily identified in AMGA, and nearly 100% in the MGACA.
Conclusions: MGA is an extremely rare lesion with a significant rate (40%) of associated atypia or carcinoma. MGA cases had a lower proliferative index (<5%) than AMGA and MGACA. All MGACA cases in our study were triple negative, consistent with a predominantly basal phenotype. Because all cases of invasive carcinoma developed from AMGA, complete excision of AMGA is warranted.
Category: Breast

Monday, March 26, 2007 11:45 AM

Platform Session: Section D, Monday Morning