An extremely rare case of metachronous multiple primary cancers of the tongue, breast, and gingiva is reported. A 61-year-old man was referred to our hospital because of a tumor of the tongue in June 2005. A clinical diagnosis of tongue cancer (T2N0M0) was made, and the patient underwent a partial glossectomy for the tongue cancer. Histopathological examination revealed a well-differentiated squamous cell carcinoma (SCC). In September 2006, left breast cancer was suspected on FDG PET-CT examination (max SUV=2.5). Physical examination showed an elastic hard mass, measuring 2.4 × 2.0 cm, under the nipple. Mammography and fine needle aspiration cytology revealed a breast cancer. A clinical diagnosis of T4bN0M0 was made, and a left mastectomy and sentinel lymph node biopsy were performed. The histopathological diagnosis was an invasive duct carcinoma (pT4bN0). HER2 was positive (HER2-FISH). Hormone receptor evaluation (Allred score) was estrogen receptor (ER) 8 and progesterone receptor (PgR） 4. Endocrine therapy with anastrozole was indicated and given for 5 years. In June 2014, an ulcerative lesion was seen on the left mandibular gingiva. A clinical diagnosis of gingival cancer (T1N0M0) was made, and marginal resection of the mandible was performed. The histopathological diagnosis was moderately differentiated SCC. The postoperative course was uneventful. There has been no evidence of recurrence, metastasis, or another primary cancer.
