Cryptococcosis mimicking pulmonary metastasis during treatment with tamoxifen for breast cancer after surgery: A case report

Pulmonary cryptococcosis (PC) of the lungs is a fungal infection often occurring in immunocompromised patients, which is most commonly contracted by inhalation. Here, we report the case of a 44-year-old woman who had undergone modified radical surgery for stage I intraductal carcinoma of the left breast one year earlier and had been undergoing endocrine therapy with tamoxifen. Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) findings indicated multiple pulmonary nodules, which was highly suspicious of lung metastasis from breast cancer. However, the pathological results suggested cryptococcus infection. The patient was subsequently treated with itraconazole antifungal therapy. However, a chest computed tomography (CT) examination one month later revealed that both lung lesions were still present. Her clinician suspected they were due to her intake of the estrogen receptor inhibitor tamoxifen and asked her to stop temporarily taking the drug. One month later, chest CT reexamination revealed that the lung lesions had disappeared. So far, there have been no reports of pulmonary cryptococcosis caused by tamoxifen after breast cancer surgery. Our case study suggests that PC infection may be one of the rare side effects of tamoxifen and should be considered in the differential diagnosis of multiple nodules in both lungs in patients with a history of cancer surgery and taking estrogen receptor inhibitors. Therefore, the etiology of infections should be considered in the differential diagnosis, especially in patients taking estrogen receptor inhibitors after tumor surgery.