We report a case of tongue carcinoma for which the pathological diagnosis reported no metastasis even though some images strongly indicated metastasis. A 60-year-old woman with a left tongue border ulcer was referred to our outpatient clinic. She had a 2×3mm ulcer with a whitish lesion on the left tongue border that contacted the lingual malposed left lower second premolar. We performed excisional biopsy and tooth extraction under general anesthesia. Pathological diagnosis showed differentiated squamous cell carcinoma with clear margins. After 4 years and 2 months, she developed lymphadenopathy in the left submandibular region. Contrast computed tomography (CT) images showed a 10 mm lymphadenopathy in the left submandibular region. Lymphadenopathy in the left submandibular and superior internal jugular regions was also detected by contrast magnetic resonance imaging. The lymphadenopathy was further identified by positron emission tomography-CT (PET-CT) , with average standardized uptake values (SUV) of 3.71 and 3.44, respectively. Because neck ultrasonography indicated a collapsed or constricted hilum of the lymph nodes, we diagnosed neck metastasis from tongue cancer as the lymphadenopathy. Under informed consent, we performed a left radical neck dissection ; 31 lymph nodes in the dissected tissue showed no cancer but rather lymphadenitis.