Nodular Goitre Posing as a Follicular Carcinoma with Extrathyroidal Extension: A Diagnostic Dilemma - A Case Report

Nodular goitre caused by thyroid hyperplasia is a benign condition arising from abnormalities in thyroid gland physiology, resulting from an imbalance between thyroid-stimulating hormone, thyrotropin-releasing hormone, and the follicular epithelium of the thyroid gland. The histopathological characteristics of this hyperplasia can resemble well-differentiated follicular carcinoma of the thyroid. Here, we present the case of a 66-year-old man with clinicopathological features suggestive of follicular carcinoma with extrathyroidal extension. However, histopathological examination confirmed nodular goitre. The diagnostic challenge was due to the presence of skeletal muscle fibres mixed with thyroid follicles, a phenomenon rarely seen in thyroid hyperplasia with very limited data available in the literature. This case highlights the diagnostic complexity of nodular goitre due to rare histopathological features mimicking follicular carcinoma.