Metachronous Sporadic Sextuple Primary Malignancies Including Bilateral Breast Cancers

Multiple primary malignancies are defined as the presence of more than one malignant neoplasm with a distinct histology occurring at different sites in the same individual. They are classified as synchronous or metachronous according to the diagnostic time interval of different malignancies. Diagnosis of multiple primary malignancies should avoid misclassification from multifocal/multicentric tumors or recurrent/metastatic lesions. In multiple primary malignancies, with increase in the number of primary tumors, the frequency rapidly decreases. Here, we report an exceptionally rare case of a woman who was diagnosed with metachronous sporadic sextuple primary malignancies including bilateral breast cancers (gastric cancer, ovarian Sertoli-Leydig cell tumor, left breast cancer, thyroid cancer, right breast cancer, and rectal neuroendocrine tumor). The sextuple primary malignancies in this case involved 5 different organs: the stomach, ovary, thyroid, rectum, and bilateral breasts. Further studies are needed to elucidate the current epidemiologic status of patients with multiple primary malignancies.