Molecular Subtypes and Ki-67 index in Breast Carcinoma with Special Emphasis on Triple Negative Breast Cancer. A 3-year Study in a Tertiary Care Center.

Molecular subtyping of breast carcinoma and Ki-67 index has gained prominence in the recent past, as conventional factors such as surgical margins, tumor size, grade and lymph node involvement, are not sufficient to assess prognosis and make better therapeutic decisions. These subtypes include Luminal A, Luminal B, Triple Negative breast cancer (TNBC), and HER2-enriched subtypes. This study aimed to analyze the molecular subtypes and Ki-67 index in prognosis of breast carcinoma. This retrospective study was conducted in the department of Pathology in a tertiary care center over a period of 3 years. All invasive breast carcinomas (IDC) which were molecularly subtyped and Ki-67 indexed were included in the study. Statistical analysis was done using SPSS software. Out of 253 cases, 231 cases (91.3%) were IDC-NST and 22 cases (8.7%) were special types. Metaplastic and papillary tumors were associated with higher grade and high Ki-67 value. TNBC (35.2%) showing a majority of high-grade tumors, was the most prevalent subtype followed by Luminal A (32%) showing low grade, unlike other studies which showed luminal A to be most common subtype. The rare PR positive subtype was also observed in our study. TNBC and HER 2-positive subtypes exhibited bad prognosis with higher histological grade, high Ki-67 index and higher age at presentation whereas Luminal A subtype, with lower grade and low Ki-67 index showed better prognosis. Thus, this vast array of predictive and prognostic information obtained by molecular subtyping will help clinicians in not only distinguishing between low-risk and high-risk subtypes but also in customization of the treatment and follow-up of the patients.