Seventeen primary malignant neoplasms involving the skin, ovary, esophagus, colon, oral cavity, and ear canal: a case report and review of the literature.

Multiple primary malignant neoplasm (MPMN) is a rare disease with two or more malignant neoplasms in one patient. In less than 0.1% of cancer patients, four or more occur. MPMN is frequently associated with hereditary cancer syndrome, although in rare cases, it is not. A female patient developed 17 MPMNs. Although they were successfully treated with surgery, radiation, and adjuvant chemotherapy, the patient died from the recurrence of ovarian cancer. To explore genetic susceptibility to MPMN, immunohistochemical analysis, microsatellite instability analysis, germ line exome sequencing, and unscheduled DNA synthesis assays were performed. However, the results of immunohistochemical analysis and microsatellite instability indicated that there were no known hereditary cancer syndromes, and exome sequencing with 88 representative genes associated with hereditary cancer syndrome revealed no variants. An unscheduled DNA synthesis assay to rule out xeroderma pigmentosum was also performed, but the result was negative. While the presence of multiple neoplasms is rare, the present case represents 17 primary neoplasms with no associations with hereditary cancer syndrome. Although the cause of MPMN was not detected in this patient, careful follow-up and deliberate cancer screening enabled successful disease management over 17 years from the appearance of the first neoplasm.