The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) is applied widely in reporting salivary gland cytology in adult population; however, there are limited publications on its application in pediatric population and consequently on risk of malignancy (ROM) for each diagnostic category. The aim of this study is to evaluate the ROM for each diagnostic category in the MSRSGC in pediatric patients from different countries using only three published original studies. FNA of the Pediatric salivary gland lesions were assessed from three different studies: 1) Maleki et al., 2) Satturwar et al., and 3) Wang et al and then classified based on the MSRSGC categories: nondiagnostic, non-neoplastic, atypia of undetermined significance (AUS), benign neoplasm, salivary gland neoplasm of uncertain malignant potential (SUMP), suspicious for malignancy (SM), and malignant. In each study, we reviewed the cases distributed according to the MSRSGC, and recorded the ROM, as well as the available histological follow-up results. The cases across the three different cohort studies showed different distributions using the MSRSGC category. The population of Maleki's cohort study had the highest total patients of around 477 cases. Also, it had the highest number of cases diagnosed as non-neoplastic (34.6%). On the other hand, the paper of Satturwar' s series, had around 32 cases that showed a predominance of benign neoplasms (34.4%). The third research paper by Wang's cohort had around 104 cases that demonstrated a higher proportion of malignant cases (5.8%) relative to total aspirates. The ROM values were also reviewed for each MSRSGC category and showed different outcomes between those three studies. The ROM of "suspicious for malignancy" and "malignant" categories reached 100% in two cohort studies done by Satturwar's and Wang's series versus 60% and 90%, respectively, in Maleki's paper. Histologic follow-up was available for 49.7% of Maleki's, 65.6% of Satturwar' s, and 51.9% of Wang's cases. The ROM for benign neoplasms was consistently low (<5-6%) across studies, while AUS and SUMP categories showed wide interstudy variability (AUS ROM: 20-100%; SUMP ROM: 31.8-67%). This study of 613 salivary gland FNAs in pediatrics confirms that the MSRSGC is applicable on pediatric population with overall high reproducibility. The ROM was lower in benign neoplasm, while it was 100% in SM and malignant categories. Variations on ROM data are most likely due to sample size differences, and patient population and surgical follow-up.

T-cell and NK-cell lymphomas are a heterogeneous group of mature lymphoid neoplasms that usually pursue an aggressive clinical course and involve both nodal and extranodal sites (Table 1). These neoplasms have diverse clinical presentations, histopathologic patterns, immunophenotypes, genetic features, and prognoses. Accurate classification, as outlined in the 5th edition of the WHO Classification of Haematolymphoid Tumours (WHO-HAEM5) and in the WHO Reporting System for Lymph Node, Spleen, and Thymus Cytopathology, requires integration of clinical information (Table 2) and the results of histopathology, immunophenotyping, viral status, and, when indicated, molecular analyses. Fine-needle aspiration biopsy (FNAB) provides a minimally invasive opportunity to sample nodal and extranodal lesions and can support either a definitive diagnosis or a highly suggestive provisional diagnosis in selected T-cell lymphoma subtypes, particularly when combined with immunocytochemistry, flow cytometry (including TRBC1), and molecular clonality testing. However, cytomorphologic overlap with reactive or other neoplastic conditions often limits the ability of FNAB alone to provide full subclassification. In this review, we summarize the cytologic features (table 3) and ancillary test profiles of T-lymphoblastic lymphoma (T-LBL), systemic anaplastic large cell lymphoma (ALCL), breast implant-associated ALCL (BIA-ALCL), nodal T follicular helper cell lymphoma, angioimmunoblastic type (nTFHL-AI), hepatosplenic T-cell lymphoma (HSTL), and peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS). For each entity, we emphasize practical diagnostic algorithms in FNAB-based cytology, typical immunophenotypic and molecular patterns, common pitfalls, and situations in which histology-preferably excisional biopsy-remains mandatory. A comparative overview (Table 4) indicates which entities can be definitively subclassified on cytology with appropriate ancillary techniques and provides examples of structured reporting according to the WHO Reporting System. FNAB, when appropriately triaged for preparation of a cell block, immunocytochemistry, flow cytometry, and molecular studies, can provide a definitive or near-definitive diagnosis in some T-cell lymphomas (e.g. T-LBL, systemic ALCL, BIA-ALCL effusions), whereas in other entities it serves mainly to raise strong suspicion and guide tissue biopsy (e.g. nTFHL-AI, PTCL-NOS). Understanding which entities can be reliably recognized by cytologic assessment, which ancillary panels are most informative, and where the limits of cytopathology lie are essential for optimal patient management and for appropriate use of the WHO Reporting System in daily practice.

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.

Background Round cell soft tissue sarcomas in the paediatric population are a common cytomorphological group of tumours. The most common entity in this group is rhabdomyosarcoma. Other representatives include Ewing sarcoma, other undifferentiated small round cell sarcomas (so-called Ewing-like sarcomas, such as CIC-rearranged sarcoma, sarcoma with BCOR genetic alterations and round cell sarcoma with EWSR1-non-ETS fusions) and desmoplastic small round cell tumour. Summary The main cell population in round cell sarcomas is composed of small round cells. Other cell morphologies may be seen in specific entities, such as spindle cells in Ewing-like sarcomas or rhabdomyoblasts in rhabdomyosarcomas. Smear backgrounds may contain varying amounts and types of stroma - for example, fibromyxoid stroma in CIC-rearranged sarcoma or sarcoma with BCOR genetic alterations or desmoplastic stromal fragments in desmoplastic small round cell tumour. Being highly cellular, cytological specimens are excellent material for molecular studies. Key messages Round cell sarcomas share many morphological similarities, so the differential diagnosis can be broad; however, subtle differences between tumours can aid the final diagnosis. Nevertheless, most round cell sarcomas require molecular studies for accurate classification, and cytological specimens are usually high quality material for such ancillary techniques.

Lymph node fine-needle cytology (LN-FNAC) is a flexible diagnostic tool capable of integrating cytological features with a wide range of ancillary tests to achieve accurate and comprehensive diagnoses. This review examines how sampling techniques, rapid on-site evaluation (ROSE), and ultrasound (US) guidance synergistically enhance the accuracy, safety, and clinical utility of LN-FNAC in everyday practice. From the earliest aspiration techniques, LN-FNAC has progressed by adopting modern sampling strategies based on ultrasound-guided trajectories, a broad selection of needle types, and variable needling approaches. Each of these components can be tailored to optimize targeting across diverse anatomical sites. The combined use of B-mode and Doppler US improves LN evaluation, allows the identification of diagnostically relevant areas, and increases the precision of needle placement, particularly in deep-seated or highly vascular LNs; in cases of partial LN involvement, US guidance allows sampling of diagnostically significant areas. Equally essential, ROSE minimizes inadequate sampling, improves diagnostic yield, and enables real-time triage for the application of specific ancillary techniques according to the initial diagnostic orientation. These techniques allow LN-FNAC to move beyond simple morphological assessment and to produce complete and clinically meaningful diagnoses. This review highlights how LN-FNAC is flexible and adaptable to a wide spectrum of clinical scenarios, from infectious and inflammatory conditions to metastatic disease and lymphoproliferative disorders. The combined strengths of US evaluation, high-precision LN-FNAC guidance and sampling, ROSE, and the selection of pertinent ancillary techniques render LN-FNAC not a simple screening modality, but a pillar of modern minimally invasive diagnostics.

Haematolymphoid lesions in serous effusion, cerebrospinal and vitreous fluid are encountered regularly. In the paediatric clinical setting, haematolymphoid lesions are the most common cause of malignant serous effusions. Cytologists and cytopathologists should be prepared to evaluate such samples as part of routine diagnostic practice. This article provides a comprehensive overview of the cytomorphological features and diagnostic considerations of lymphomas involving serous fluids, cerebrospinal and vitreous fluids. B-cell non-Hodgkin lymphomas are most often encountered in fluid cytology specimens. A practical method for triaging lymphocyte-predominant effusions involves assessing lymphoid cell size, specifically distinguishing between small-to-medium and large lymphoid cells. A significant differential diagnosis of small-medium lymphoid cells in fluid specimens is reactive lymphocytosis while that for large cells is metastatic malignant, and atypical or malignant mesothelial cells. Cytologic evaluation of fluids containing lymphocytes provides valuable information regarding the nature of these lesions. Accurate cytologic diagnosis, with clinicopathologic correlation and judicious use of ancillary testing where possible, is essential for identifying the underlying cause of effusion, guiding therapy, monitoring disease progression or relapse, and informing prognosis. To optimize diagnostic outcomes, proper collection, transport, and preparation of fluid specimens is required. Collaboration with haematopathologists and use of standardised cytologic reporting systems further contribute to diagnostic accuracy and consistency. Emerging technologies, including molecular profiling, liquid biopsy, single-cell multi-omics and artificial intelligence, offer promising avenues for advancing the diagnosis and prognostication of haematolymphoid malignancies in fluid-based samples. Further research will determine their clinical utility.

Recent advances in pathology have expanded our understanding of cytogenesis, morphologic features, molecular classification, and biological behavior of tumours. Consequently, histological classification of thyroid neoplasms has become more precise, making cytological diagnosis more challenging. The Focus on Cytomorphology with the Professor Slide Seminar at the 22nd International Congress of Cytology addressed this issue by presenting 4 cases, emphasizing subtle morphologic clues, use of ancillary testing, and the value of clinicopathologic correlation. Cribriform morular thyroid carcinoma (CMTC), previously categorized under papillary thyroid carcinoma (PTC) is now classified as tumour of uncertain histogenesis. Awareness of key cytological features, correlation with ultrasound findings, and supportive immunocytochemistry for beta-catenin and/or estrogen receptors led to the correct diagnosis. Hyalinizing trabecular Tumour (HTT) shares nuclear features of PTC and diagnosis on cytological specimens is challenging, potentially resulting in a false positive diagnosis. However, recognition of elongated/polygonal cells with peculiar intra-trabecular hyaline material is a clue to its diagnosis. Molecular studies demonstrating GLIS gene rearrangements (PAX8::GLIS3 and PAX8::GLIS1) are specific for HTT. High-Grade Differentiated Thyroid Carcinoma (HGDTC) retains the features of differentiated carcinoma and also shows high-grade features. However, the high-grade features may not be apparent on cytological specimens, making the presurgical cytological diagnosis very challenging. Furthermore, there is pathobiologic heterogeneity among the subtypes of HGDTC with the diffuse sclerosing subtype of HGDTC behaving less aggressively. Columnar cell carcinoma (CCC-PTC) is a rare subtype of PTC that is characterized by hypercellularity and pseudostratification. Co-expression of TTF-1 and CDX-2 is a useful clue to its diagnosis.