Pathologists often have a dilemma is a lymph node biopsy reactive or corresponds to a lymphoproliferative or other malignant disease. In everyday routine work, we rely on morphologic criteria and immunohistochemical analyzes. In better-equipped labs additional cytogenetic and molecular methods are used if morphology and immunohistochemical analyzes are not sufficient for getting correct diagnoses. It is important to know clinical presentation and the opinion of a clinician who runs the case. In reactive lymph nodes general morphology is mostly preserved. Distribution of B and T cells, histiocytes, dendritic cells and proliferation is adequate. Foreign cells are not present. Ways of reaction in lymph nodes are follicular hyperplasia, paracortical expansion, sinus histiocytosis and granuloma formation. If metastases are present, most often from carcinomas and melanomas, the initial deposits are usually sub capsular or less often in sinuses. One should be careful to differentiate sinus histiocytes and metastatic tumor cells, what can easily be verified by immunohistochemical stains.If it is a lymphoma, one should decide is it a Hodgkin or a non-Hodgkin lymphoma. In non-Hodgkin lymphomas, one should decide between small cell and large cell lymphomas. In non-Hodgkin lymphomas, tumor cells are dominant and background inflammation is scant and mostly consisted of small T cells and rare histiocytes. In T cell lymphomas background inflammation can be quite various. In Hodgkin lymphomas background inflammation most often is various and almost always outnumbers tumor cells. Tumor cells are large, with lobulated or multiple nuclei and conspicuous nucleoli. The immunophenotype is usually clearly different from non-Hodgkin lymphomas. The differentiation of small cell and large cell non-Hodgkin lymphomas is easily made by comparing cell sizes. If tumor cell size is closer to size of histiocytes or endothelium it is a large cell lymphoma, but if it SPECIJALNA SESIJA: KATEDRA ZA PATOLOGIJU MEDICINSKOG FAKULTETA, UNIVERZITETA NOVI SAD, SRBIJA 31 MATERIA MEDICA • Vol. 34 • Issue 1, suplement 1 • april 2018. is closer to small lymphocytes and red blood cells it is a small cell lymphoma. Differentiation of small cell lymphomas is based on morphology, distribution of cells and on immunophenotype. Differentiation of large cell non-Hodgkin lymphomas requires immunohistochemical analyzes because morphology is often very similar among entities. Correct diagnosis is important due to application of optimal therapy and reaching the best prognosis for the patient.

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.