Clinicopathologic analysis of invasive micropapillary differentiation in breast carcinoma

Invasive micropapillary carcinoma (IMPCa) of breast is histologically chara cterized by growth of cohesive tumor cell clusters within prominent clear s paces resembling dilated angiolymphatic vessels. In this study, eighty thre e breast carcinomas with IMPCa differentiation were identified by review of the invasive carcinoma cases in our institution and correlated retrospecti vely with standard clinicopathologic parameters and survival status relativ e to a control series of cases (mean follow up 7 years). IMPCa growth patte rn was present in 6% of all breast carcinomas; it was generally a focal com ponent in otherwise typical invasive ductal carcinoma. It comprised more th an 80% of the total neoplasm in only 10 cases (12%), 50-80% of the neoplasm in 7 cases (8%), 20-50% of the neoplasm in 22 cases (26%) and less than 20 % in 44 cases (53%). The mean tumor size was 4 cm, 22% invaded skin, and 58 % were poorly differentiated, but 71% were ER positive. Axillary node metas tases were present in 77% of cases, were typically multiple (51% had three or more positive), and usually contained an IMPCa component (81% of the cas es). There was no significant difference in node status, ER status, size, t umor grade, or peritumoral angiolymphatic invasion between tumors with pred ominant (more than 50%) v/s focal IMPCa components. In both groups 46% of t he patients died from their disease (mean interval to death = 36m). Skin in volvement and nodal status were the only parameters which predicted poor su rvival (P = .01). The outcome of patients with IMPCa did not differ signifi cantly from infiltrating ductal carcinomas of similar node status. In concl usion, our results suggest that IMPCa growth pattern may be a manifestation of aggressive behavior, as shown by frequent skin invasion and extensive n odal involvement. However, clinico-pathologic features and outcome of IMPCa are not strongly dependent on the relative amount of micropapillary compon ent.