This research aims to study the histological grade of breast adenocarcinoma and state of lymph node involvement, and correlating them with primary tumor size to assess if the latter can aid as guideline in deciding surgical option for treatment. This study was implemented immunohistochemistry laboratories of Al-Sadder Teaching Medical City in Al Najaf during the period from September 2020-september 2021, forty-four women with breast carcinoma who undergone modified radical mastectomy were involved in this study, aged between 29 -81 years, mean age being 47.3 years. we divided study group into two categories; depending on tumor size, with cutoff point of 2 cm. Histological grade and lymph nodes metastases were assessed and comparison done between these two groups. Majority of cases in our study were histologically grade 3(68.18%), each of grade 1 and 2 constituted 15.9%. Lymph node metastases noticed in 63.63%. Our results showed a significant difference between the two patient groups regarding axillary lymph node metastasis (P<0.05), but no statistically significant difference found between the two patient groups regarding histological grade (P>0.05). Many of the tumors in Iraqi patients are rapidly progressive, and therefore need a modern approach in their treatment and that tumor size can't be considered as dependable parameter in determining the type of surgical operation.