<prompt> An elderly male presents with 4x5 cm lump in right neck. FNAC revealed it to be squamous cell carcinoma. No primary was found. A diagnosis of unknown primary was made. According to AJCC system of classification, the TNM staging of the tumor w ould be:T1 N2 MoT0 N2a M1T1 N2c MoT0Na Mx  <response>: Ref: Haas , Hoffmann TK, Engers E Ganzer V. Diagnostic strategies in cen-ical carcinoma of an unknown primary CUP. EurAnch Otorhinolaryngol 2002 Jul;2596:325-33NCCN guidelines 2014AJCC 2010Explanation:CARC INOMA OF UNKNOWN PRIMARY CUP TNMAJCC 2010 STAGINGStage Information for Metastatic Squamous Neck Cancer with Occult Primary.PRIMARY TUMORT0: Patients with unknown primary tumor.Tx: Patients whose tumor cannot be assessed or is not assessed.REGIONAL LYMPH NODESN0: No regional node metastasis.Nx: Regional nodes cannot be assessed.Nl: Single ipsilateral node, 3 cm.N2a: Single ipsi lateral node. 3 cm and 6 cmN2b: Multiple ipsilateral nodes. 6 cm.N2c: Contralateral or bilateral nodes. 6 cm.N3: Node 6 cm.METASTASISM0: No distant metastasis.Ml: Distant metastasis.Mx: Unknown presence or absence of metastasis could not be assessed. 