Spontaneous breast cancer remission: A case report

INTRODUCTION: Spontaneous 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 CASE: A 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. DISCUSSION: There 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. CONCLUSION: We report a rare case of spontaneous remission in which the cancer disappeared on pathological examination although the cytological diagnosis had been malignant.