[299] Microinvasive Lobular Carcinoma of Breast: Characterization of a Rare Entity Based on a Clinicopathological Profile of Fifteen Cases

DS Ross, SA Hoda. Weill Cornell Medical College, New York

Background: Clinicopathological data on MicroInvasive (<0.1cm) Lobular Carcinoma (MILC) of Breast is scarce, and as such this pathological entity remains poorly characterized.
Design: All available clinical and pathological material on cases in which MILC was either suspected or diagnosed over an eighteen-year period (1991-2009) was reviewed. Only cases wherein the final diagnosis of MILC could be indisputably established by 2 observers, and confirmed via appropriate immunostains (cytokeratin (+), one or more myoepithelial markers (-), and E-cadherin (-)) were included. Cases wherein a larger invasive tumor was identified in a subsequent specimen were excluded.
Results: Fifteen (15) cases were confirmed to be MILC (in a search of 47,547 breast cases). Mean age of patients was 52 (range 41-65). Presentation included radiographic abnormality in 8 cases and mass in 3 (no such information in 4 cases). MILC was unilateral in all 15 cases (right: 7, left: 8). Mean number of microinvasive foci was 1.5 (range 1-5). All foci of MILC were intimately associated with lobular carcinoma in situ (LCIS). The associated LCIS was of classical type in all 15 cases, and nuclear grade of MILC cells and adjacent LCIS was low to intermediate. Synchronous pleomorphic LCIS existed in 1/15 (7%) case. Neither stromal reaction nor inflammatory infiltrate was present in any case and the only histological hint of MILC was enhanced stromal cellularity. Three cases had synchronous DCIS of solid, cribriform or micropapillary types. Each of 8 MILC cases, wherein results could be obtained, were found to be positive for estrogen receptor (ER) and progesterone receptor (PR) (MILC was not present in ER and PR stained sections of 7 cases). Her-2/neu was not overexpressed in each of 7 cases wherein results could be obtained (MILC was not present in HER-2/neu stained sections of 8 cases). The final surgical procedure was excisional biopsy (8 cases), ipsilateral mastectomy (5), and bilateral mastectomies (2). Eight of 15 cases had residual LCIS or atypical lobular hyperplasia. Ten of 15 cases had axillary lymph node dissection (with sentinel node biopsy in 8), with all lymph nodes being negative. All patients remain alive with no evidence of recurrence/metastases on a mean follow-up of 24 months (range 1-72 months).
Conclusions: MILC is a rare, histologically subtle, lesion associated with classical LCIS. MILC appears to be a low-morbidity disease with neither recurrences nor metastases observed (at least in the short term).
Category: Breast

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 39, Tuesday Morning


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