Primary non‐hodgkin malignant lymphoma of the breast: An immunohistochemical study of seven patients and literature review of 152 patients with breast lymphoma in Japan

Background. The breast is rarely primary site for extranodal malignant lymphoma. Most reported primary non‐Hodgkin malignant lymphomas of the breast (PBL) are of B‐cell phenotype. Methods. Histologic and immunohistochemical analyses of seven patients with PBL and statistical analysis of 152 patients with PBL reported in the Japanese literature were performed. Results. Malignant lymphoma could not be predicted preoperatively with clinical and radiologic findings; breast carcinoma, fibroadenoma, and phyllodes tumor were the preoperative diagnoses. All patients were women; they ranged in age from 31 to 80 years (mean, 57.6 years). The right breast was involved initially in five patients. In four, only the breast was involved (Stage I), whereas in three, the ipsilateral axillary lymph nodes (Stage II) were involved at diagnosis. According to the Working Formulation, all patients belonged to the intermediate grade and were classified as having diffuse large cell (five patients) or mixed (two patients) lymphoma. Immunophenotypic analysis revealed that all patients had B‐cell lymphoma. No patients had lymphoepithelial lesions, which is the characteristic feature in categorizing lymphoma as mucosa‐associated lymphoid tissue (MALT) lymphoma. A statistical analysis of the patient reported in the Japanese literature has divided PBL into two types: bilateral type that affects younger women and unilateral type that has broad age distribution, but preponderantly occurs in older women. The age and stage at diagnosis were significant prognostic factors in predicting the survival time, but the location and size of the tumor at initial presentation, histopathologic type, terminal leukemic manifestation, and treatment modality were not. Conclusions. This study indicates that most PBL are diffuse large cell lymphoma of B‐cell phenotype and that the age and stage at diagnosis are significant prognostic factors.