Spontaneous regression (SR) of cancer is a rare but well-documented biological phenomenon. However, the mechanism remains to be elucidated. We herein report a case of the SR of breast cancer at both the primary site and metastatic axillary lymph node with spontaneously-induced T cell-mediated immunological responses. A 52-year-old female with a lump in the left axilla was diagnosed to have a small breast carcinoma with a distinct axillary lymph node metastasis. During the preoperative systemic examination, she was diagnosed to have severe type 2 diabetes mellitus, was treated with insulin, and the hyperglycemia was normalized after one month. Surgery for left breast cancer was then performed. The postoperative histopathological examination revealed the SR of breast cancer at both the primary site and metastatic axillary lymph node. Immunohistochemical studies revealed that estrogen receptor positive, AE1/AE3-positive ductal carcinoma completely underwent necrosis associated with extensive infiltration of CD3-positive T cells in the tumor nodule in the lymph node. In addition, primary ductal carcinoma cells also underwent single cell necrosis with infiltration of T cells with lymph follicle-like organization of B cells in the mammary gland. The features were suggestive that the tumor eradication in the metastatic lymph node and regression of the primary ductal carcinoma could be due to host T cell response to the ductal carcinoma. As far as we know it is the first report that shows the spontaneous regression of breast cancer, probably due to the spontaneously-induced T cell response.
Keywords: Spontaneous regression; T cell response; breast cancer; cancer immunology.