PET/CT Detection of Epstein–Barr Virus–Positive Lacrimal Sac Carcinoma in Unknown Primary Cervical Nodal Metastasis

A 55-year-old man presented with a left submandibular mass. Biopsy revealed metastatic carcinoma, later confirmed by immunohistochemistry as Epstein–Barr virus (EBV)-positive nonkeratinizing squamous cell carcinoma, possibly of nasopharyngeal or pulmonary origin. Despite elevated serum EBV-DNA (79.1 copies/mL), nasopharyngeal endoscopy and biopsies were normal. 18 F-FDG PET/CT revealed an FDG-avid nodule in the left lacrimal sac and hypermetabolic cervical nodes. Surgical resection confirmed EBV-encoded RNA (EBER)-positive undifferentiated carcinoma in the lacrimal sac and metastasis in lymph nodes. This case highlights the lacrimal sac as a rare primary site of EBV-associated carcinoma and the utility of 18 F-FDG PET/CT in detecting occult primaries.