Diagnostic difficulties with lymphoid infiltrates

Abstract

Diagnostic dilemmas associated with the presence of lymphoid cells in FNAC samples are usually considered to be associated with the diagnosis of lymphomas. However, whilst the majority of lymphomas can be diagnosed without difficulty, there are other aspects of lymphoid infiltrates in FNAC samples that may be either misleading or difficult. The lecture will give examples of the conditions where observing the details of lymphoid infiltrates may be important in making the diagnosis, in particular: granulomatous infiltrates, lymphoid infiltrates in extranodal sites and neoplasms containing lymphocytes. Granulomatous infiltrates: tuberculosis, sarcoidosis, Kikuchi‐Fujimoto disease, SLE, multicentric Castleman's disease, cat‐scratch disease, all can be diagnosed with FNAC as can leishmaniasis, Kimura's disease and sinus histiocytosis with massive lymphadenopathy. Malignant lymphomas and solid tumours may be also associated with epithelioid granulomata. The finding of lymphoid cells in FNAC samples of extranodal sites e.g. thyroid, salivary gland, breast is always noteworthy. In these cases lymphoid cells may define the underlying pathology and contribute to accurate diagnosis. The presence of non‐circulating lymphoid cells indicates presence of lymphoid follicles and may be significant for diagnosis. Neoplasms containing lymphoid cells may be either lymphomas or other non‐haemopoetic neoplasms which typically contain lymphocytes as part of their morphological appearances. According to the WHO, morphological diagnosis of NHL relies largely on cytological detail, although the development of new technologies has helped to define several clinical entities. Cytological assessment of the sample taken with FNAC is often the first line morphological investigation of lymphoma achieving the overall accuracy rate of 79∼90% for high grade NHL and Hodgkin–s disease (with the exception of the LP). The examples of solid neoplasms containing lymphocytes are: acinic cell carcinoma, paediatric follicular carcinomas, lymphoepithelioma‐like carcinoma, seminoma, sebaceous lymphadenoma, Warthin–s tumour, thymoma and others.