Observational Study of Diffuse Large B Cell Primary Breast Lymphomas Treated With RCHOP +/- XRT

Inclusion Criteria: * Previously untreated patients with DLBCL of the breast. * Patients must have CD20 positive tumors. * Stage IE or IIE. * Must have at least one objective measurable or evaluable disease. Baseline measurements and evaluations must be obtained within 4 weeks of registration to the study. * Patients must not have historical or radiographic evidence of CNS metastasis including previously treated, resected or asymptomatic brain lesions or leptomeningeal involvement. * Patients must have an ECOG performance status 0-2. * Patients must have adequate organ function as evidenced by the following laboratory studies (within 2 weeks prior to registration): * Creatinine Clearance \>= 50 ml/min * Total bilirubin \<= 2.0 mg/dl and AST \<= 2 x upper limit of normal. If documented hepatic involvement with lymphoma, total bilirubin can be \<= 3 x \*ULN, and AST \<= 5 x ULN. * Absolute neutrophil count \>= 1500/mm3 and platelet count \>= 100,000/mm3. If documented bone marrow involvement with lymphoma, absolute neutrophil count \>= 500/mm\^3 and platelet count \>= 50,000/mm\^3. * Patients must be age \>= 18 years. * Women must not be pregnant or breast feeding due to potential harmful effects to the fetus/baby. Women of childbearing potential and sexually active males are strongly advised to use an accepted and effective method of contraception. * Patients must not have an active infection requiring parental antibiotics. * Patients with known HIV infection are excluded. * Patients must have a normal left ventricular ejection fraction to be eligible.