PREPARATION OF SPECIMENS FOR HISTOLOGY AND CYTOLOGY

The diagnosis of hematolymphoid tumors requires a combination of morphological, immunophenotypic, molecular genetic and clinical data. Successful morphological analysis is easiest to achieve by examination of intact lymph nodes that have been excised whole with the capsule intact. Fragmentation, while difficult to avoid in some areas (such as the mediastinum), inhibits analysis. Core biopsies are increasingly used for the diagnosis of lymphoid-related conditions, but these should be restricted to cases in which nodal excision is difficult or impossible, due either to access-related problems (intra-abdominal location) or to patient-related factors. Core biopsies, by their very nature, represent a small percentage of the lesional tissue and may fail to demonstrate focal variations in the tumor such as a diffuse component in follicular lymphoma. Fine needle aspiration (FNA) cytology has a role to play in the diagnosis of lymphoid pathology, but is best performed where there is access to high-quality flow cytometry that allows immunophenotyping of the lymphoid cells. FNA is particularly useful in the head and neck region for the exclusion of metastatic tumour.

Choice of the lymph node for sampling is of great importance. Where there is choice of areas the inguinal region is best avoided, as these nodes frequently show distortion of the normal architecture by fibrosis. Cervical lymph nodes are most easily interpreted.