Spontaneous breast cancer remission: A case report

•Spontaneous cancer remission without treatment is a known phenomenon with various types of cancer.•Although spontaneous breast cancer remission has been thought to be a rare, this may occurs at a certain rate(not rare phenomenon).•When cancer was not detected in the pathological specimen and there were no known biological markers to provide information for the decision regarding adjuvant therapy, observation without further treatment can be option.

IntroductionSpontaneous breast cancer remission is a rare phenomenon. We report the disappearance from the remaining breast of a new primary carcinoma that had been confirmed through cytology of a pathological specimen, in a case that is strongly suspected to be spontaneous remission.Presentation of caseA 44-year-old woman underwent breast-conserving surgery for a tumor located on the border between the upper-outer and lower-outer quadrants of the left breast (T2, N1, M0; Stage IIB). Eleven years after surgery, computed tomography indicated a mass in the upper-inner quadrant of the left breast. Excisional biopsy was initially planned for treatment following the definitive diagnosis because cytology revealed malignancy. The patient had noticed tumor regression one month after fine-needle aspiration and repeat ultrasonography performed the day before excisional biopsy confirmed the tumor reduction. On pathological examination, no tumor cells were observed in the mass.DiscussionThere was a discrepancy between FNA cytology and pathological diagnosis in our patient. The cytological findings indicated malignancy, but the pathological findings did not. When a tumor’s pathological diagnosis is not malignant even though its FNA cytology diagnosis was malignant, sampling error, cytological over-diagnosis or some other error may have occurred. In this case, however, these were not detected. Because fibrosis was visible on pathological examination, we believe that these events corresponded to spontaneous remission.ConclusionWe report a rare case of spontaneous remission in which the cancer disappeared on pathological examination although the cytological diagnosis had been malignant.