Diagnostic approaches, traps, and pitfalls in the FNAC diagnosis of lesions of the spleen

Splenomegaly, presenting as diffuse enlargement, nodules, or masses, may occur in different clinical contexts and can be caused by a wide range of conditions, including increased splenic function, hematological diseases, cysts, vascular lesions, and inflammatory or infectious processes. Most of these entities, particularly inflammatory and vascular conditions, are diagnosed clinically or radiologically and do not require further investigation. Conversely, some nodular or diffuse lesions, mainly lymphomas, metastases, nonspecific lymphocytic hyperplasia in specific clinical settings, and other rare or equivocal entities, still require direct evaluation by fine-needle aspiration cytology (FNAC), core-needle biopsy (CNB), or endoscopic ultrasound-guided FNAC (EUS-FNAC). Because of the infrequent clinical indication, FNAC of the spleen (sFNAC) has never achieved a clearly defined role in the diagnostic work-up of splenomegaly and has not become as widely used as in other organs. Nevertheless, sFNAC has been successfully applied in various clinical contexts for the diagnosis of splenomegaly and of different pathological processes, although it is not free from diagnostic traps and pitfalls. This review provides a comprehensive evaluation of the cytomorphological features of sFNAC across different pathologies and clinical settings.