P065 Luminal A vs luminal B: impact of different St. Gallen Ki67 and PgR cut points in the TEAM study

Goals: Metaplastic carcinoma is distinct albeit, rare and aggressive formof invasive breast cancer. Histologically, these tumors exemplify enrichment of tumor initiating markers such as CD44 and ALDH1 along with low expression of CD24. Our aim was to review clinico-pathological and outcome data of patients diagnosed with metaplastic carcinoma at Aga Khan University and to correlate immunohiostochemical expression of CD44, CD24 and ALDH1 with overall survival. Methods: Cases were identified through breast cancer registry from 2000–2013. Immunohistochemical staining for CD44, CD24 and ALDH1 was performed on 5um serial sections of archival tumor blocks. Data was analyzed on SPSS 19 and overall survival was estimated by Kaplan–Meier. Results:Metaplastic carcinoma was diagnosed in 25 female patients with mean age of 54.6 years. Eighty-eight percent (22/25) cases had grade III tumors. ER and PR expression was observed in 52% and 36% cases, respectively. HER-2/neu overexpression and amplification was identified in 4% (1/25) and 13.3% (2/15) patients, respectively. Stage I disease was found in 4% (1/25) patients, 52% (13/25) had stage II, 36% (9/25) had stage III and 8% (2/25) patients had stage IV disease. Mean duration of follow-up was 23 months. Systemic recurrence developed in 24% (6/25) patients. Overall death rate was 28% (7/25). Membranous expression of CD44 was seen in 94% tumors whereas cytoplasmic expression of CD24 and ALDH1 was observed in 63% and 26.3% tumors, respectively. Six cases revealed CD44/ALDH1−/CD24− expression. Twopatients in this subgroup expired due to systemic metastasis, whereas the remaining 4 patients remained event free. ALDH/CD44/CD24 pattern of expression was observed in 4 patients and 1 patient in this subgroup expired due to systemic progression of stage IV disease. No significant difference was identified in median survival between CD44/CD24−, ALDH1−/CD24 and CD44/ALDH groups. Conclusion: In this study, prevalence of metaplastic carcinoma was 1.17%. Majority of patients presented with stage II disease and hormone receptor positivity. CD44 expression was detected in all except one tumor. ALDH1−/CD24 subgroup was associated with lower median overall survival however this was not statistically significant. Disclosure of Interest: No significant relationships.