Context: Breast tumors are common worldwide, and various reports suggest an increasing incidence in Nigeria, which necessitates an urgent need to differentiate benign from malignant tumors. Aims: To classify, grade and to determine the changing pattern, frequency, age and sex distribution of breast tumors seen in a tertiary hospital. Materials and Methods: This was a 10-year retrospective study of all breast tumors diagnosed at the Pathology Department of a Teaching Hospital from 1 January 2001 to 31 December 2010. Results: A total of 1,566 breast tumors were diagnosed during the study period, of which 1035 (66.1%) were benign, and 531 (33.9%) were malignant. Fibroadenoma was the commonest benign breast tumor followed by fibrocystic change, and they accounted for 47.1% and 25.4% of benign breast tumors respectively. Out of the 531 malignant cases reviewed; 496 (93.4%) were females, and 35 (6.6%) were males with a female to male:ratio of 14.2:1.0. The age range of malignant cases was between 21 and 79 years with a mean age of 42.0 years. Invasive ductal carcinoma was the predominant histological type with 316 cases (59.5%). This was followed by medullary carcinoma with 61 (11.5%) cases, invasive lobular carcinoma and invasive papillary carcinoma each with 37 (6.9%) cases. Three hundred and ninety-eight cases satisfied the criteria for grading, out of which 237 (59.5%) cases were classified in Grade 1, 133 (33.4%) cases in Grade 2 and 28 (7.1%) cases in Grade 2. Conclusions: Breast tumors are quite common which are mostly benign and are seen in both sexes with a striking female preponderance. The findings are generally similar to most previous studies from Nigeria, Africa and western world with minimal variations.