Cancers of unknown primary localization (CUPL) are a heterogeneous group of metastatic neoplasias for which a standardized diagnostic examination did not determine the primary localization of the origin. In 5% of histological form of CUPL is squamous cell carcinoma, which, in the case of an isolated lesion of the cervical lymph nodes is treated as a "favorable phenotype". Tactics of treatment of such a CUPL is suggested in both primary local squamous cell carcinoma (SCC) of the, head and neck with regional lymph nodes involvement (T1-3N1-3M0) and in 25% -30% of patients leads to a 5-years survival rate. This calls for the use of an immunohistochemical method for the accurate verification of the histological form of an isolated metastasis of the cervical lymph nodes and use of the appropriate therapy. In the work 62 samples of isolated lesions of the cervical lymph nodes with carcinomas without another established primary localization for the period 2015-2017 were investigated. The control group consisted of 12 samples of SCC of the head and neck of the known localizations. The immunohistochemical panel of markers included Cytokeratin Pan, Vimentin, CD45, S100, Cytokeratin HMW, Cytokeratin 7, Cytokeratin 20, p63, TTF1. The parameters of the areas, perimeters and “roundness” of the nucleus were determined in the ImageJ program. The aim of the study was to investigate the complex of morphological, morphometric and immunohistochemical characteristics of SCC without primary localization with isolated lesion of the cervical lymph nodes, in comparison with other histological forms and control group of SCC of the head and neck of the known localizations to improve diagnostic algorithms. A difference in the distribution of histological forms for all CUPL with isolated lesion of the cervical lymph nodes was determined in the predominance of SCC, in comparison with the general distribution of histological forms for all CUPL. Similarity of morphometric parameters of metastatic SCC of subgroup 1 (phenotype of Cytokeratin, Pan AE1 / AE3 (+) / Cytokeratin HMW (+) / p63 (+) / Cytokeratin 20 (-) / TTF1 (-) / Vimentin (- / +) / Cytokeratin 7 (- / +)) with samples of the control group of SCC of the head and neck of known localizations. The established decrease in the size and "roundness ratio" of the nuclei of the SCC cells is a reflection of the weighting of cellular atypia and correlates with the polymorphism of the nuclei and decrease in the degree of differentiation of the SCC.