Branchial cleft cysts are congenital anomalies derived from the branchial apparatus, most commonly presenting as lateral neck masses. Intrathyroidal localization is exceedingly rare and may mimic malignancy both radiologically and cytologically-particularly when squamous cells are identified and misinterpreted as malignant. Surgical resection is often required to achieve a definitive diagnosis. Our report highlights the diagnostic challenges of such lesions and underscores the importance of integrating clinical, cytological, and imaging data.

Although cytology has long been regarded as a traditional diagnostic tool, its development has varied across different healthcare systems. This review outlines the historical evolution and contemporary practice of cytology in Taiwan, addressing both gynecologic and non-gynecologic cytology. Cytology was first introduced to Taiwan in the 1950s with early contributions from specialists in pathology, pulmonology, gynecology, and endocrinology who established diagnostic services and training programs. These initiatives enhanced diagnostic accuracy, informed clinical management, and, through policy-driven cervical cancer screening programs, contributed to a substantial decline in disease incidence and mortality. Progress was further consolidated by the implementation of quality assurance protocols and the formal training of cytotechnologists. The adoption of internationally recognized reporting frameworks, such as the Bethesda, Paris, and Milan systems, has aligned local practice with global standards. Technological innovations, including liquid-based cytology, cell block techniques, and rapid on-site evaluation, have become integral to routine workflows, reinforcing diagnostic reliability. More recently, advances in digital cytopathology and artificial intelligence are beginning to reshape diagnostic practice and quality control.

A 51-year-old man with no significant past medical history presented with worsening epigastric pain radiating to the back, exacerbated by inspiration.

This report describes the cytologic features of cholangioblastic intrahepatic cholangiocarcinoma, a distinct subtype of cholangiocarcinoma from a 32-year-old female with a past medical history remarkable for sclerosing mesenteritis who presented with abdominal pain for several days. Abdominal MRI revealed an 8.5 cm central hepatic mass. Fine needle aspiration (FNA) and concurrent biopsy of the liver mass were performed. The FNA smear showed a monotonous population of singly scattered to loosely cohesive epithelioid to focally plasmacytoid tumor cells with round to oval nuclei, a fine chromatin pattern, and scant to moderate cytoplasm. Prominent nucleoli, mitotic figures, and necrosis were not identified. Focally, an acinar/glandular pattern was identified. Based on cytomorphology, an initial impression of low-grade neuroendocrine tumor was favored. The concurrent biopsy showed tumor cells arranged in trabecular, acinar to solid growth patterns. Immunohistochemical stains performed on the concurrent biopsy showed that the tumor cells were diffuse and strongly positive for CAM 5.2, CK7, albumin ISH, inhibin, and focally positive for synaptophysin and CD56. The tumor cells were negative for chromogranin, arginase, glypican-3, CD34, INSM1, GATA3, PAX-8, SF-1, SALL4, HepPar1, and CDX2. The overall findings were consistent with intrahepatic cholangiocarcinoma, cholangioblastic variant. To our knowledge, this case represents the first report of the cytologic features of a cholangioblastic variant of intrahepatic cholangiocarcinoma on FNA.

Asteroid bodies are rare cytoplasmic inclusions within multinucleated giant cells, most classically associated with sarcoidosis but also encountered in other granulomatous and reactive conditions. Their recognition in cytology is uncommon and diagnostically challenging. We present the case of a 30-year-old female with a post-traumatic forehead swelling in which fine needle aspiration cytology (FNAC) revealed numerous foreign body-type giant cells containing asteroid bodies. This case highlights the cytomorphological spectrum of asteroid bodies outside systemic sarcoidosis, their differential diagnoses, and their clinical relevance.

This report introduces Dr. Sara E. Monaco, the incoming President-Elect of the American Society of Cytopathology (ASC) and System Director of Cytopathology at Geisinger Medical Center. Dr. Monaco has provided significant mentorship to me over the years and facilitated the development of my passion for cytopathology and education.

Our descriptive study focused on morphologic characteristics of hyperchromatic crowded groups (HCGs) in ThinPrep cervical cytology tests when reviewed with the artificial intelligence (AI)-assisted Hologic Genius Digital Diagnostics System (HGDDS).

To describe the long-term clinical outcomes of women diagnosed with human papillomavirus type 31 (HPV 31) infection and to assess its potential implications for genotype-specific cervical cancer risk stratification in a real-world screening setting.

Fine-needle aspiration cytology (FNAC) remains widely used for the evaluation of palpable breast lesions, particularly in resource-limited settings, though histopathology is the gold standard. The International Academy of Cytology (IAC) Yokohama System provides a standardized five-tier reporting framework with defined risk of malignancy (ROM). This study aimed to evaluate its diagnostic performance, reproducibility, and applicability in a tertiary care setting.

Rosette-forming epithelioid osteosarcoma is an extremely rare type of osteosarcoma. This report describes a man in his early 50s with a destructive right iliac bone/acetabulum mass showing osseous destruction and extensive soft tissue involvement. Cytohistologic examination revealed osteosarcoma with epithelioid neoplastic cells arranged in rosettes. The neoplastic cells were immunoreactive for SATB2, TTF1, and CDX2. The osteoid was better appreciated in the H&E-stained materials. The cytohistological features, immunohistochemical profile, and differential diagnoses are discussed. Attention to details regarding the identification of osteoid in both cytology and histology materials is emphasized.

NUT carcinoma (NC) is a rare and highly aggressive type of poorly differentiated carcinoma that originates from undefined anatomical sites, primarily in midline structures of the upper respiratory tract. We report the case of a male patient in his fifth decade of life who is a non-smoker. He presented with symptoms of dyspnea and cough, and had previously been treated for an atypical infectious process. A PET scan revealed a right pulmonary hilar mass alongside pathological lymphadenopathy. An endobronchial ultrasound-guided fine needle aspiration (EBUS-FNA) of the subcarinal lymph node was performed, followed by a cytomorphological evaluation in situ (Rapid On-Site Evaluation-ROSE) for sample management. The smear showed high hypercellularity with loosely cohesive cells arranged mostly in a single-cell pattern, exhibiting a poorly differentiated appearance. Immunohistochemical studies on the cell block indicated nuclear positivity for NUT expression, confirming the diagnosis of pulmonary NC. Poorly differentiated high-grade neoplasms in middle-aged patients present a significant challenge when the tumor sample is limited. The cytopathologist's role is to optimize the available material for a complete and accurate diagnosis, which is essential for appropriate treatment.

Fine needle aspiration cytology (FNAC) is widely used to evaluate various lesions. Rapid on-site evaluation (ROSE) can be incorporated into cytology procedures. Our study aims to determine the efficacy of ROSE on the specimen adequacy of FNAC as compared to non-ROSE cases.

Extra-gastrointestinal stromal tumours (EGIST), especially pancreatic EGIST (pEGIST), are exceedingly rare and have unknown metastatic potential. We report a cytodiagnostically challenging case of a metastatic pEGIST diagnosed from the hepatic metastatic site. A 40-year-old male presented with fever, abdominal pain and deranged liver function tests. Radiology revealed an ill-defined mass in the pancreas with multiple metastatic foci. Due to the inaccessibility of the primary lesion, fine needle aspiration cytology (FNAC) was performed on the liver lesion, which revealed a tumour with an epithelioid to spindle-cell morphology, lacking a mesenchymal matrix, causing diagnostic ambiguity between an epithelial and mesenchymal neoplasm. An extensive immunopanel on the cell block with strong CD117 and DOG1 expression confirmed a metastatic Gastrointestinal Stromal Tumour (GIST), excluding other differentials. This case underscores the utility of FNAC and immunochemistry on the cell block in diagnosing uncommon cases where only cytological samples from minimally invasive procedures are available.

Pancreatic medullary carcinoma is an extremely rare tumor classified as a histological subtype of pancreatic ductal adenocarcinoma. We report a case of a pancreatic medullary carcinoma and describe its cytological features. A 75-year-old woman presented with lower back pain, epigastric discomfort, and a tumor-like lesion in the pancreatic body. Cytologic specimens obtained via endoscopic ultrasound-guided fine-needle aspiration revealed relatively uniform small round cells with a high nuclear-to-cytoplasmic ratio, appearing as isolated scattered cells or loosely aggregated small clusters in a bloody background containing mature lymphocytes. Histological examination showed cells similar to those observed in the cytological smear, and molecular testing revealed wild-type KRAS and high microsatellite instability. Consequently, the patient was diagnosed with pancreatic medullary carcinoma. To our knowledge, only 33 cases of pancreatic medullary carcinoma have been reported to date, and this is the first report to describe its cytological features.

Cribriform Morular Thyroid Carcinoma (CM-TC) is a rare thyroid malignancy characterized by distinctive histomorphologic and genetic features, primarily driven by continuous activation of the WNT/β-catenin signaling pathway. However, diagnosis can be challenging on fine needle aspiration biopsy due to its rarity and overlapping cytomorphologic features with other thyroid tumors. We present a unique case of CM-TC displaying long papillary fronds and intracytoplasmic globules, reminiscent of solid pseudopapillary tumor of the pancreas. These two cytologic features have not been previously described in the literature. Molecular analysis (ThyroSeq) revealed an activating CTNNB1 (beta-catenin) exon 3 mutation in this case, which is also commonly observed in solid pseudopapillary tumors of the pancreas. We propose that morphologic similarity may be a consequence of a similar mutation. Recognizing these novel characteristics may aid in distinguishing CM-TC from other thyroid tumors, improving diagnostic accuracy and patient management.

Male breast cancer (MBC) is a rare disease accounting for less than 1% of breast cancers and for 0.11% of all male malignancies. Despite the fact that the epidemiologic, clinical, and therapeutic literature regarding female breast cancer is well documented, little is known about the features of male breast cancer. Here, we present a case of cytological pleural metastasis from ductal breast carcinoma in a 55-year-old man. Immunohistochemical staining showed that the tumor cells were positive for BerEp4, GATA-3, AE1/AE3, CAM5.2, ER (70%), AR (10%), PR (10%), and ki67 (10%). In our experience, effusion cytology remains an accurate tool for the diagnosis of metastatic carcinomas.

Mentorship has been a cornerstone of my professional development in cytopathology, shaping both my diagnostic acumen and academic identity. Under the guidance of Dr. Claire Michael during residency and fellowship, I was introduced to a culture of intellectual rigor, systems thinking, and continuous improvement. Her mentorship on diagnostic refinement and molecular innovation laid the foundation for my scholarly growth in cytopathology. Later, as I transitioned into faculty life, Dr. Jonas Heymann became a peer mentor whose collegial support and shared inquiry helped me navigate independent practice. Together, we explored diagnostic reproducibility and quality assurance in thyroid cytology with an innovative approach. This narrative reflects the transformative power of mentorship across career stages and its enduring impact on professional growth.

Extramammary Paget's disease (EMPD) of the vulva is a rare intraepithelial adenocarcinoma with a typically indolent course. Distant metastasis, particularly to supradiaphragmatic lymph nodes, is exceedingly uncommon and poses a significant diagnostic challenge.

Solitary fibrous tumors (SFT) are a rare neoplasm of mesenchymal origin. SFT was previously described primarily in the pleura and meninges; however, extrapleural and extra-meningeal SFT have been reported in almost every anatomic site and account for up to 40% of cases. The most significant histologic findings of SFT include spindle cell proliferation in a "pattern-less pattern", dilated and branching "staghorn"-like vasculature, and ropey collagen deposition. However, these findings are not consistently present in every case of SFT and may also be seen in other diseases. SFT has a characteristic NAB2::STAT6 gene fusion and nuclear overexpression of STAT6. The rarity of the disease, broad range of differential diagnoses, and wide spectrum of cytomorphological and histologic findings make the diagnosis of extrapleural SFT, especially on a fine needle aspiration (FNA) specimen, challenging. Recognizing and including this entity in the differential is necessary before the final diagnosis may be achieved through proper immunohistochemical and molecular workup. In this paper, we present two cases of extrapleural SFT with unusual locations: the first is a primary SFT present in a parotid gland and the second is a metastatic SFT present as two solid pancreatic masses.

Fine-needle aspiration cytology (FNAC) is a vital first-line diagnostic tool in evaluating lymphadenopathy, particularly in the head and neck region, where malignancies often present with nodal enlargement. Historically, the lack of a standardised reporting system for lymph node cytology has resulted in interobserver variability and inconsistent diagnoses. The Sydney System, introduced in 2019, provided a structured five-tier framework, which was further refined by the newly proposed World Health Organisation (WHO) Reporting System for Lymph Node, Spleen, and Thymus Cytopathology (2024). This study aims to assess the diagnostic performance of the proposed Sydney system in the context of head and neck lymphadenopathy and determine the associated risk of malignancy (ROM) for each diagnostic category.

Over four decades, Korea has advanced from a limited cytology service to a global model of digital and AI-integrated cytopathology. Since the founding of the Korean Society for Cytopathology (KSC) in 1986, a nationwide framework has been established-encompassing standardized practices, systematic education for specialists and cytotechnologists, and nationwide cervical screening through the National Cancer Control Program. A mandatory Quality Assurance Program (QAP) launched in 2005 ensured consistent diagnostic quality, achieving an unsatisfactory Pap test rate below 0.2% and cytology-histology discrepancy under 0.6% among over 10 million annual examinations. The 2021 STANBAI project digitized two decades of QAP slides into a standardized whole-slide image (WSI) archive, driving the development of multiple AI models. In parallel, the CytoAcademy web/mobile platform enabled interactive WSI-based education and global participation by over 200 institutions. Korea has also shared this model internationally through on-site and virtual programs in low-resource countries. By integrating national QA, digital infrastructure, AI innovation, and global training, Korea has built a future-ready cytopathology ecosystem-enhancing diagnostic precision and offering a scalable blueprint for global implementation.