[105] Invasive Ductal Carcinoma with Lobular Features Can Be Diagnosed on Breast Core Biopsies and May Be Important To Distinguish from Pure Invasive Ductal Carcinomas

David Arps, Celina Kleer, Judy Pang. University of Michigan, Ann Arbor, MI

Background: Invasive ductal carcinoma with lobular features (IDC-L) is not recognized as a distinct subtype of breast cancer by pathologists. It is a category used when there is the presence of both ductal and lobular histology in the same lesion. In routine practice, many of these tumors are diagnosed as mammary carcinoma with ductal and lobular features, IDC-L, or classified as ductal or lobular type arbitrarily. A study at our institution on resection specimens suggested that IDC-L may be a distinct variant of invasive ductal carcinoma (IDC), with more than 90% of cases being E-cadherin positive, but has clinicopathological characteristics more similar to invasive lobular carcinoma (ILC). In addition, re-excision rates for obtaining negative margins were higher for patients with IDC-L (49%) in our series than the overall rate of re-excisions for our institution (25%). We sought to determine the accuracy of diagnosing IDC-L on core biopsies, as patients with IDC-L may need further margin evaluations, and their eligibility for specific treatments may depend on the diagnosis (e.g. cryotherapy and partial breast radiation such as mammosite used for IDC are not recommended for patients with IDC-L).
Design: 183 cases of IDC-L from 1996-2011 were identified from the pathology database. 149 cases had core biopsies. Cases initially diagnosed as IDC on core biopsy were re-reviewed. Available slides from resections were previously reviewed (n=150). Lobular features were defined as small cells individually dispersed, arranged in linear cords, or in loose aggregates without the formation of tubules or cohesive nests.
Results: IDC-L was diagnosed on core biopsies in 92 cases (62%), while 44 (29%) were diagnosed as IDC, ten (7%) as ILC, one as poorly differentiated carcinoma, and two as ductal carcinoma in-situ (DCIS). Of the 44 core biopsies diagnosed as IDC, 30 cases with available slides were re-reviewed and of those, 24 (80%) were re-classified as IDC-L. Of the remaining six cases, four had slides available for review from their resection. Three cases had < 30% lobular morphology on the resection. One case had 90% lobular morphology on resection; however the biopsy target was for calcifications on mammogram and the core showed predominantly high grade DCIS with only a small focus of invasive carcinoma.
Conclusions: IDC-L can be diagnosed on core biopsies with good correlation on resection and may be important to distinguish from IDC as there are treatment and prognostic implications.
Category: Breast

Monday, March 4, 2013 1:00 PM

Poster Session II # 37, Monday Afternoon


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