The ocult primary tumor.
D000328:Adult; D000368:Aged; D001706:Biopsy; D003937:Diagnosis, Differential; D004724:Endoscopy; D005260:Female; D006258:Head and Neck Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D006801:Humans; D007223:Infant; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D037981:Neck Dissection; D009362:Neoplasm Metastasis; D013964:Thyroid Neoplasms / Q000175:diagnosis; D013997:Time Factors