What is the role of histopathology in the diagnosis and management of thyroid nodules?

Role of Histopathology in Diagnosis and Management of Thyroid Nodules

Histopathology plays a critical role primarily after initial cytological assessment by fine-needle aspiration cytology (FNAC) in thyroid nodules. FNAC results are categorised using the Royal College of Pathologists modification of the British Thyroid Association (BTA) system, ranging from Thy1 (inadequate) to Thy5 (malignant), guiding further management steps ¹.

When FNAC results are indeterminate or suspicious (Thy3a, Thy3f, Thy4, Thy5), histopathological examination of surgically excised tissue (diagnostic hemithyroidectomy or total thyroidectomy) is essential to establish a definitive diagnosis and guide treatment ¹. For example, Thy3f (suggesting follicular neoplasm) typically leads to diagnostic hemithyroidectomy for histopathological evaluation ¹.

Histopathology confirms malignancy, determines tumour type, and assesses features such as capsular or vascular invasion, which are crucial for staging and prognosis. This information directs further management, including the extent of surgery and the need for adjuvant therapies like radioactive iodine ¹.

In cases where FNAC is inadequate (Thy1), repeat sampling or diagnostic surgery may be considered to obtain tissue for histopathological diagnosis ¹. Thus, histopathology is the definitive diagnostic tool following cytology and is integral to planning appropriate surgical and oncological management of thyroid nodules ¹.