Lymph nodes Fine Needle Cytology in the diagnosis of infectious diseases: cytological and histological correlations.

Fine Needle Cytology (FNC) is often used in the diagnosis of lymph node enlargement as first diagnostic procedure. In some cases different cytological features may occur, with different histological aspects. In other cases, FNC samples are neither representative nor sufficient to exclude a possible lymphoproliferative process or a metastasis. In these cases, specific ancillary techniques such as microbiological tests, immunocytochemistry, flow cytometry or molecular biology procedures may be used to assess the benign reactive nature of lymph node enlargement, allow clinical surveillance and avoid surgical biopsies. Cytology and ancillary techniques may also identify, in selected cases, possible aetiological agents. Notwithstanding these procedures, FNC unsolvable cases may occur; in these cases, indication for a direct histological examination should be promptly given in order to avoid any delay to further investigations and appropriate treatments. This study reports the most common cytological patterns occurring in reactive lymph nodes as well as ancillary techniques required in different conditions. Lymph nodal FNC should be performed by expert cytopathologists ensuring a safe and correct execution and a rapid evaluation of the smears for the assessment and the application of specific ancillary techniques.