Adenomyoepithelioma (AME) of the breast is a rare type of benign breast tumor. Many AMEs show benign behavior, but reports of the malignant type are rare. We present the case of a patient with AME with repeated local recurrences and further malignant transformation. A 53-year-old woman visited our hospital with a 16-mm palpable mass in the right breast. A core needle biopsy was performed. The pathological diagnosis was AME. Lumpectomy with a safety margin was performed without axillary lymph node dissection (ALND). Two years later, local recurrence developed, and the patient again underwent lumpectomy with a safety margin. The pathology showed malignant AME, and the margin was negative. Eight months later, local recurrence developed again in the same location, and a total mastectomy was performed without ALND. The pathological diagnosis was malignant AME. The patient was disease-free for three years posttreatment. The treatment of AME requires caution, as it may exhibit repeated recurrences after local excision as well as malignant transformation.

Neoadjuvant chemotherapy (NAC) has become a standard therapy for patients with advanced breast cancer. Pathological complete response (pCR) after NAC is an important prognostic indicator, but some patients with pCR continue to experience recurrence. So new predictive and prognostic markers in addition to pCR are needed following NAC for breast cancer. Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) can evaluate metastases in the entire body simultaneously, and has several potential advantages over conventional imaging modalities. The purpose of this study was to evaluate whether FDG-PET/CT can determine NAC response and whether FDG-PET/CT can be a new prognostic marker. We imaged 83 breast cancer tumors with FDG-PET/CT, ultrasound (US), and magnetic resonance imaging (MRI) to evaluate NAC efficacy. As we previously analyzed 110 breast cancers with FDG PET/CT, we defined a threshold of >1.7 maximum standardized uptake value (SUVmax) as abnormal fluorodeoxyglucose (FDG) uptake. After NAC, 16 (19.3 %) tumors had a complete response, 54 (65.1 %) had a partial response, 11 (13.3 %) showed stable disease, and 2 (2.4 %) showed progressive disease. One of the two patients with progressive disease had bone metastasis detected by FDG-PET/CT and was not operated on. Remote metastases were evident in 2.4 % of patients after NAC as determined by FDG-PET/CT. Overall, 17 patients had pathological complete response (pCR). The sensitivity of abnormal FDG uptake after NAC for non-pCR was 20.3 % and the specificity was 94.7 %. Patients with abnormal FDG uptake after NAC experienced significantly more recurrences (P = 0.004) and more of them died (P = 0.010). Moreover, the difference in disease-free survival was more significant in the estrogen receptor (ER)-negative group. FDG-PET after NAC may be more effective for predicting prognosis than for evaluating treatment response. This tendency was particularly remarkable in ER-negative breast cancer tumors. FDG-PET/CT is useful for reevaluating surgical applicability after NAC.