Molecular Profiles of Breast Cancer in Ilorin, Nigeria.

1602 Background: Breast cancer is a complex disease with diversity between tumors and within tumor. Major differences exist in incidence and mortality rates across populations, making it imperative to investigate molecular pathogenesis in various populations. Methods: To identify molecular subtypes of breast cancer we collected Formalin-fixed and Paraffin-Embedded (FFPE) tissue blocks from Ilorin. Pathologic features and patients' data were extracted from histology reports. Tissue microarrays were constructed from FFPE tumor samples and adjacent normal breast tissue at the University of Chicago. Immunohistochemical assays were performed using a DAKO immunostainer (DAKO, Carpinteria, CA) with antibodies and antigen unmasking. Breast cancer subtypes were defined as luminal A (ER+ and/or PR+, HER2-), luminal B (ER+ and/or PR+, HER2+), basal-like (ER-, PR-, HER2-, CK5/6+, and/or EGFR+), HER2+/ER- (HER2+, ER-, PR-), and unclassified (negative for all five markers). Results: From 2003 to 2007, 203 histologicaly confirmed breast cancer patients were enrolled, including 5 males and 5 bilateral breast cancers. Median age at diagnosis was 46 yrs. Majority of patients (59%) presented with large tumors (≥ 5 cm) as median time from symptoms onset to cancer diagnosis was 6 months (interquartile range 3-12 months). Proportion of ER+, PR+ and HER2+ tumors were 27%, 16%, and 30%, respectively. Commonest breast cancer subtype was basal-like (25%), followed by unclassified (24%), luminal A (20%), HER2+/ER- (19%), and luminal B (11%). Patients with ER+ tumors had longer duration of symptoms (median 8 months) than patients with ER- tumors (5 months) but ER+ patients had smaller tumors (median 5 cm) than ER- patients (6 cm, p = 0.02). Conclusions: This study replicates previous findings that triple negative breast cancer was over-represented in African population in a different geographic region of North Central Nigeria as found in the Southwest earlier on. Patients seek medical help after many months of cancer symptoms, suggesting lack of awareness of breast cancer in the population. Study also showed that ER- breast cancer grows faster than ER+ breast cancer, underscoring urgent need to develop effective breast cancer awareness and early detection programs in Africa. No significant financial relationships to disclose.