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.

Hydatid disease caused by Echinococcus granulosus is a major health problem in endemic regions. Hepatic cysts may mimic simple cysts or neoplasms, creating diagnostic challenges. Fine needle aspiration cytology (FNAC) provides a rapid diagnosis, but its role remains debated due to variable sensitivity and concerns regarding safety. We retrospectively analyzed 15 patients with hepatic and hepatobiliary cystic lesions evaluated in our pathology department over a five-year period. Fourteen patients underwent ultrasound-guided FNAC, and one patient had an incidental retroperitoneal mass biopsied during cholecystectomy. Smears were stained with May-Grünwald-Giemsa (MGG) and examined for protoscolices, laminated membranes, scolices, hooklets, and background inflammatory response. Biopsy tissue was processed with hematoxylin-eosin (H&E). The cohort included 14 FNAC cases, 7 (50%) demonstrated diagnostic features of Echinococcus, while 7 (50%) yielded only histiocytes, necrotic debris, or nonspecific inflammation. The biopsy revealed chronic cholecystitis with echinococcal structures. The patient developed postoperative complications and died on postoperative day 2. FNAC provides a rapid and specific diagnosis of hepatic hydatid cysts when characteristic elements are identified, but half of aspirates may be nondiagnostic. Our findings highlight both the utility and limitations of FNAC, and underscore the importance of multimodal correlation with imaging, serology, and histopathology for safe and accurate patient management.

Background Lymphoepithelial carcinoma of the lung shows distinctive histologic features but its cytologic description is limited in the literature. This study reviews and compares a large cohort of lung and lymph node aspirates, bronchial, serous fluid, and sputum exfoliative cytology from histology-proven cases, aiming to detail diagnostic features and cytologic specimen types preferable for diagnosis of this entity. Methods Cytology specimens of patients with a histologic diagnosis of lymphoepithelial carcinoma on lung biopsy or resection were reviewed for cytomorphologic features associated with lymphoepithelial carcinoma, with comparison between cytologic specimen types performed. Results Totally 13 aspiration (7 lung and 6 lymph node) and 22 exfoliative (18 bronchial, 1 serous fluid and 4 sputum cytology) specimens were reviewed. The most common cytomorphologic features observed were macronucleoli (82.9%), marked nuclear membrane irregularity (82.9%) and naked tumor nuclei (74.3%). High cellular cohesion, presence of large tumor fragments, rich lymphoid background, and tumor-infiltrating lymphocytes, are also frequently seen (>60%). Lymphoid components, multinucleated tumor cells and large epithelial fragments were more commonly seen in aspirations compared to exfoliative specimens (p<0.05). Conclusion Distinctive morphological features of lymphoepithelial carcinoma of lung are reproducible on cytologic specimens. Qualitative nuclear features (macronucleoli, marked nuclear membrane irregularity and naked tumor nuclei) are the most consistently observed. Compared to exfoliative cytology, aspirated specimens show higher yield for diagnostic cytomorphologic features of lymphoepithelial carcinoma.

The World Health Organization (WHO) Classification of Female Genital Tumours, Fifth Edition (2020), proposed a classification of uterine cervical glandular lesions according to whether they are associated with human papillomavirus (HPV) or not. The WHO recommends HPV genetic screening as an initial test that should be followed by cytology as a triage test in HPV-positive patients. We selected 40 cytological specimens of HPV-associated glandular lesions including atypical glandular cells, adenocarcinoma in situ (AIS), and adenocarcinoma. We confirmed their histological type using biopsy or excisional specimens. We examined the cytological features of the glandular lesions in detail. The majority of HPV-associated adenocarcinoma was usual-type adenocarcinoma with enlarged nuclei, increased nuclear density, and heterogeneous to pale nuclear chromatin and most cases showed apoptosis or mitosis. AIS exhibited stacked clusters with intense nuclear chromatin, so-called hyperchromatic crowded groups. AIS showed less nuclear pleomorphism compared to invasive adenocarcinoma and no background tumor diathesis. Conversely, adenocarcinoma tended to have a tumor diathesis. Stratified mucin-producing carcinoma had a foamy to vacuolated cytoplasm and tended to form nested clusters without a palisade arrangement. Some atypical glandular cells were found to have glandular involvement of high-grade squamous intraepithelial lesions by histology. To contribute to the early detection of glandular lesions, it is important to recognize the fundamental cytological features, especially hyperchromatic crowded groups, background tumor diathesis, and nuclear findings.

Cytological examination of a fine needle aspirate (FNA) is a minimally invasive modality that is increasingly used in the diagnosis of lymphoma. Flow cytometry and other ancillary tests make an important contribution to the diagnostic value of FNAs of lymphoid lesions. This review follows the recent publication of the first edition of the WHO Reporting System for Lymph Node, Thymus and Spleen Cytopathology. This WHO volume provides a framework for assessment of cytopathological samples, and presents in detail the contribution of ancillary studies, including flow cytometry. The current review is designed to complement the WHO volume. It presents criteria for adequacy of FNA specimens assessed by flow cytometry, and includes strategies to determine the degree of blood contamination of FNA samples. Evidence for the contribution of flow cytometry to the diagnostic value of FNA is reviewed. The role of TRBC1 and TRBC2 in the assessment of T cell populations is presented. Strengths of flow cytometry, along with its limitations, are presented. Provided these limitations are properly understood, the inclusion of flow cytometry as an ancillary modality makes a substantial contribution to FNA assessment.

Fine-needle aspiration cytology (FNAC) is a minimally invasive and reliable technique for sampling lymph nodes, thymus, and spleen. However, morphological interpretation alone is often insufficient due to overlapping features among reactive, infectious, and neoplastic processes. To review the essential role of ancillary testing in enhancing the diagnostic accuracy of FNAC in lymphoid and mediastinal organs. A narrative review of the literature focusing on the applications, strengths, and limitations of flow cytometry, immunocytochemistry, in situ hybridization, and molecular testing in FNAC samples from lymph nodes, thymus, and spleen. Ancillary studies significantly increase the diagnostic precision of FNAC, enabling lineage assignment, clonality determination, detection of defining genetic alterations, and identification of therapeutic biomarkers. These techniques are particularly valuable in paucicellular aspirates, mediastinal lesions, splenic lymphomas, and cases with overlapping morphological patterns. Integration of ancillary techniques with cytomorphology aligns FNAC with modern WHO and IAC-IARC-WHO diagnostic frameworks, transforming it into a powerful multiparametric tool that supports accurate diagnosis, subclassification, prognostication, and treatment planning.

Cytological examination of lymph nodes and serous effusions is of value in the diagnosis of small B cell lymphomas. The World Health Organization (WHO) has recently published a reporting system relating to the cytological examination of lymph nodes, spleen and thymus to standardise the approach to reporting such specimens. An overview of the WHO reporting system is given with particular reference to the diagnosis of small B-cell lymphomas. The role of rapid on site evaluation and ancillary testing is discussed. The cytomorphological features of specific small B-cell lymphomas and associated ancillary testing are described. The WHO reporting system provides a standardised approach to the reporting of cytological specimens from lymph nodes, the spleen and the thymus. Small B-cell lymphomas pose a challenge to the cytopathologist due to their morphologic overlap with each other and reactive conditions. The importance of correlation and integration of cytomorphological appearances with clinical features and ancillary testing modalities to obtain a final diagnosis on cytology specimens is emphasized. The present review includes a description of cytomorphological features according to pattern recognition and provides an overview of diagnostic criteria for specific entities based on cytomorphology alone and in combination with ancillary tests in different clinical settings discussing differential diagnoses and potential pifalls.

Pediatric lung and mediastinal tumors constitute a rare and heterogeneous group of neoplasms, often of embryonal, germ cell, lymphoid, or mesenchymal derivation. Cytology (especially fine-needle aspiration) plays a critical role in the minimally invasive diagnosis of these masses, particularly in children, where surgical biopsy may carry a high risk. This review synthesizes the cytomorphologic spectrum of pediatric thoracic tumors, emphasizing distinguishing features, common pitfalls, and the integration of ancillary studies (immunocytochemistry, molecular testing). Special focus is on pleuropulmonary blastoma, inflammatory myofibroblastic tumor, germ cell tumors, lymphomas, Langerhans cell histiocytosis, neurogenic tumors, and small round cell tumors. We propose a structured diagnostic algorithm that incorporates clinical, radiologic, and cytologic data, and review the emerging roles of next-generation sequencing, AI-assisted cytology, and liquid-based methods in pediatric thoracic cytopathology. Accurate cytologic diagnosis in pediatric thoracic masses demands optimal sampling, careful morphologic assessment, and judicious use of ancillary techniques. Improved standardization, multicenter collaborations, and integration of digital/molecular tools hold promise to enhance diagnostic yield and guide therapy in this challenging realm.