Mucinous Breast carcinoma is rare malignant breast neoplasm and it constitute only 1-2 % of all invasive breast cancers. Tumor called as Pure mucinous breast cancer when mucinous component is 90% of the tumor. We present a case report of 36-year-old female patient with approximately 3x2 cm size mass on left breast. Lumpectomy specimen of breast with wide local excision received. This tumor was classified as grade 1 (well differentiated) according to modified scarf bloom Richardson grading system. Mucinous breast carcinoma commonly observed in old aged female. This type tumor of tumor usually shows immune histochemistry positivity for ER, PR and HER2 negative which indicate towards good prognosis. Pure mucinous breast carcinoma is very rare entity among all infiltrating breast carcinoma. It is very rarely observed in young age female patient & prognosis is excellent if diagnosed correctly. Therefore, we present this rare case report in this journal.