[149] Mucinous Carcinoma of the Breast: A Clinico-Pathological Assessment Based on the Percentage of Mucinous Component

Zohreh Eslami, Gulbeyaz Omeroglu, Atilla Omeroglu. McGill University Health Center, Montreal, QC, Canada

Background: Mucinous carcinoma (MC) of the breast is a rare disease and can be divided into 3 categories based on the extent of mucinous component: 90% or more mucin (Pure Mucinous Carcinoma / PMC), 50- to 90% mucin (Mixed Mucinous Carcinoma /MMC) and less than 50% mucin (Ductal Carcinoma with Mucinous Features / DCMF). In this study we have compared the three categories of MC analyzing clinical and pathological parameters.
Design: Our database (2006-2011) was searched for breast cancers containing a mucinous component. Tumors were compared based on ER/PR/ HER2 status, tumour size, grade, patient age, Breast Imaging Reporting and Data System (BIRAD) classification and lymph node status. In addition a Ki67 stain was performed on PMC cases to evaluate its correlation with HER status. The percentage of Ki-67 positive cells was identified using a computerized system.
Results: A total of 97 of breast cancers with a mucinous component have been identified: 45 cases of PMCs (46%), 17 cases of MMCs (18%) and 35 cases of DCMF (36%). Her-2 was positive in four cases of PMC (9%), two DCMF (6%) and one MMC (6%). Lymph node metastasis was higher in MMC (7/17, 41%) compared to PMC (1/45, 2%) and DCMF (4/35,11%). There was no significant difference in ER/PR status between the three entities. The average age at diagnosis was 72 for DCMF, 70 for PMC and 67 for MMC. Ki67 proliferative index was slightly higher in Her2 negative PMC (5.02) than Her2 positive PMC (4.36). BIRAD scores for MMC was: 4B:18%, 4C:18%, 5:41%, N/A:23%, for PMC: 4A:11%, 4B:18%, 4C:18%, 5:27%, 6:7%, N/A:18%, and DCMF: 4A: 9%, 4B:11%, 4C:11%, 5:35%, 6:14%, N/A:20%. The average tumor size was 1.9 cm for PMC and DCMF and 2.2 cm for MMC. Tumor grades were as follows: PMC (52%:1, 43%:2, 7%:3), MMC (76%:2, 24%:1), DCMF (69%:2, 20%:1, 11%:3).
Conclusions: Classifying MCs based on percentage of mucinous component identifies three categories of tumors with distinct pathological and clinical characteristics. DMCF occurs in older patients and are higher grade tumors. Tumor size and incidence of lymph node metastasis are greatest in MMC group. MMC is also more likely to have a BIRAD 5 score. Unexpectedly, Her2 positivity is more common in PMC group. Ki67 proliferative index does not correlate with Her2 positivity in PMC.
Category: Breast

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 22, Monday Morning


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