Insights into thyroid and salivary gland cytopathology: highlights from a 45th ECC slide seminar.

Introduction: Thyroid and salivary gland cytopathology frequently present diagnostic challenges due to complex presentations, overlapping features between benign and malignant conditions, particularly with grey-zone entities and rare pathologies. To address these issues, the 45th European Congress of Cytology (ECC) held a slide seminar focused on challenging cases. This article reviews key findings from the six cases discussed, emphasizing the importance of a comprehensive diagnostic approach. The objective of this article is to illustrate the diagnostic challenges of rare thyroid and salivary gland lesions through case presentations, showing the need for a comprehensive, multidisciplinary approach to accurately reach a final diagnosis and steer the patient's management.

Case presentation: The seminar presented cases involving fine-needle aspiration cytology (FNAC) followed by histopathological correlation, molecular and cytogenetic analyses or immunohistochemistry (IHC) markers to elucidate cytomorphological features, differential diagnoses, and final diagnoses of rare cases in thyroid and salivary gland cytopathology. Challenging thyroid cytology cases included differentiating thyroid sarcoidosis from malignancy, identifying intrathyroidal ectopic thymus versus lymphoid neoplasms, and recognizing poorly differentiated thyroid carcinoma initially misinterpreted as a benign follicular neoplasm. Complex salivary gland cases addressed the distinction of basal cell adenocarcinoma from adenoid cystic carcinoma, metastatic SMARCB1-deficient carcinoma diagnosed via immunohistochemistry and a parotid mass initially identified as a Warthin tumor.

Conclusion: These cases highlight the critical role of integrating cytological, clinical and histopathological data to navigate the diagnostic complexities of thyroid and salivary gland lesions. A multidisciplinary approach and standardized algorithms are essential for improving diagnostic accuracy and patient outcomes.