[Case of Tongue Cancer That Was Considered to Be a Metachronous Double Cancer with Parotid Gland Cancer].

In Japan, the incidence of double cancers is increasing due to the rise in cancer prevalence in the super-aging society, and the frequency is particularly high among patients with head and neck cancer. To the best of our knowledge, there has been only 1 reported case of metachronous double cancer with parotid gland cancer and tongue squamous cell carcinoma, and herein we report the outline of this case. The patient was a 70-year-old male with a smoking history. In 2017, a total parotidectomy and neck dissection for adenocarcinoma of the right parotid gland were performed at the otolaryngology department, followed by concurrent chemoradiotherapy as postoperative therapy. Pathological examination revealed adenocarcinoma NOS(pT4aN2bM0, Stage ⅣA). There was no recurrence or metastasis, and the patient was recovering well. However, in October 2022, the patient presented to the hospital with a chief complaint of pain at the right margin of the tongue. At the initial consultation, an ulcerative lesion with a slightly unclear boundary and maximum diameter of approximately 15 mm was observed on the right margin of the tongue. Since epithelialization was observed in some regions, it was diagnosed as intractable stomatitis and the patient was put under observation for the time being. With no signs of healing during the follow- up examination a month later and considering the possibility of malignant tumors, a total excision of tongue lesion was performed. Pathological examination revealed well-differentiated squamous cell carcinoma(pT1N0M0, Stage Ⅰ). Going forward, we plan to conduct careful follow-up observations with the possibility of further metachronous double cancer occurrences in mind.