Background& Objective: Determining the risk of distant metastasis in invasive breast cancer patients with lesions measuring 40 mm or less, and comparing the risk between quadrantectomy with axillary dissection and modified radical mastectomy with axillary dissection. Materials & Methods: The study was performed prospectively by evaluating a random sample of invasive breast cancer patients with lesions measuring 40 mm or less, who presented to Al-Byroni University Hospital in Damascus during one year between 9/8/2009 and 9/8/2010. Results: Ninety-four breast cancer patients were evaluated. The median age of patients was 54 years. Excisional biopsy was the most common diagnostic tool (41%), and frozen section was used in 27% of patients. The tumor was located in the upper lateral quadrant in 65% of patients. The tumor was in stage one in only 13% of cases, and most tumors were in stage II (63%). Modified radical mastectomy with axillary dissection was performed in 62 patients (66%), and quadrantectomy with axillary dissection was performed in 32 patients (34%). The patients were followed for up to 18 months. Distant metastasis were observed in 8 patients (13%) from the first group and 6 patients (19%) of the second group. Conclusion: There is no important difference of risk of distant metastasis after modified radical mastectomy or quadrantectomy in breast cancer lesions measuring 40 mm or less. We recommend quadrantectomy as the first-line surgical treatment for breast cancer when indicated.