Rare Entities of Thyroid Gland: A Series of Twelve Cases

Thyroid disorders are frequently encountered in clinical practice, with hypothyroidism and hyperthyroidism representing the most common manifestations. However, beyond these frequently diagnosed disorders exists a group of rare thyroid lesions that present unique and often formidable diagnostic and therapeutic challenges. Despite their infrequent occurrence, these rare lesions carry significant clinical importance due to their potential for misdiagnosis, variable behaviour, and the complexity of their management. This retrospective case series examines a diverse group of rare thyroid lesions diagnosed over three years, in a tertiary care centre in South Kerala, to underscore their clinical relevance and emphasise the necessity for heightened diagnostic vigilance. In this series, the author explores 12 different conditions, which include a variety of uncommon pathologies such as dyshormonogenetic goitre and follicular adenoma with bizarre nuclei, along with several histological variants of Papillary Thyroid Carcinoma (PTC), including the tall-cell, columnar-cell, Warthin-like, and diffuse sclerosing subtypes. In addition, authors also describe cases of rare thyroid malignancies, such as the papillary variant of Medullary Thyroid Carcinoma (MTC), collision tumours, cribriform morular thyroid carcinoma, high-grade follicular carcinoma, poorly differentiated carcinoma, and anaplastic carcinoma. These cases were observed in patients ranging from 14 to 77 years of age, highlighting that such lesions can occur across a broad age spectrum. Due to their overlapping clinical and cytological features with more common thyroid conditions, accurate diagnosis of these rare lesions depends heavily on comprehensive histopathological examination, meticulous tissue sampling, and adjunctive Immunohistochemical (IHC) studies. Failure to recognise these entities can lead to misdiagnosis, delayed treatment, and suboptimal patient outcomes. This case series emphasises the critical need for increased awareness among clinicians and pathologists regarding the presentation and management of rare thyroid lesions. Early identification and tailored therapeutic strategies are essential to improving prognostic outcomes. By shedding light on these infrequent but clinically significant conditions, this study advocates for the integration of detailed histological analysis and advanced diagnostic techniques into routine thyroid pathology assessments.