Background: Pathological complete response (pCR) to Neo adjuvant chemotherapy (NACT) is a signicant prognostic marker in breast cancer, so accurate diagnosis and grading of pathological chemo response of tumour is needed for an effective planning of treatment regimen. To study the various histopathological Aims: changes in Mastectomy specimens following NACT and to evaluate the pathological response of tumour to NACT, also to compare the expression of ER, PR, and HER2 in biopsies and post NACT mastectomy specimens by Immunohistochemistry (IHC). Methods And Materials: 50 breast carcinoma cases, who was diagnosed on trucut biopsies and treated with preoperative NACT followed by mastectomy was included. In post NACT mastectomy specimens, the chemoresponse was classied according to Union for International Cancer Control (UICC) guidelines. ER, PR, and HER2/ neu receptor expression was compared between trucut biopsy specimens (pre- NACT) and resection specimens (post- NACT). Results were analysed by Chi square test and McNemar chi square test. Among 50 cases, patients presented with lump, Results: involved more on the right and in upper outer quadrant. Most common stage at presentation is stage III A. Histologically all belong to IDCC -NST histological subtype. Signicant reduction in mean tumour size by 52.7% after NACT was observed. pCR, pPR and pNR was observed in 20 %, 58 % and 22 %of the cases respectively. Most common histological change seen in post NACT is necrosis, desmoplasia, brosis, lymphocytic inammatory response. Discordance in ER expression (17.5 %), PR expression (20%) and HER2 /neu (12.5 %) before and after NACT. But these were statistically insignicant. CONCLUSIONS: Pathological evaluation of chemo response of tumour is the gold standard. The discordance rate of ER, PR and HER-2/neu expression following NACT was statistically insignicant, larger studies needed to analyse their impact in patient management.