UPSC-CMS 2018 — Pathology

Question 1: Fine Needle Aspiration Cytology (FNAC) is NOT conclusive in which one of the following thyroid swellings?

• A. Papillary carcinoma thyroid
• B. Follicular carcinoma thyroid (Correct Answer)
• C. Thyroiditis
• D. Medullary carcinoma thyroid

Explanation: ***Follicular carcinoma thyroid*** - FNAC cannot definitively distinguish between a **follicular adenoma** and a **follicular carcinoma** [1]. - This is because the diagnosis of follicular carcinoma relies on the presence of **capsular invasion** or **vascular invasion**, which can only be assessed on **histopathological examination** of the resected specimen, not cytology [1]. *Papillary carcinoma thyroid* - FNAC is highly effective in diagnosing papillary carcinoma due to characteristic **nuclear features** such as **Orphan Annie eye nuclei**, nuclear grooves, and intranuclear inclusions [3]. - These distinct cytological findings allow for a confident diagnosis without needing to assess invasion [3]. *Thyroiditis* - FNAC is typically conclusive for diagnosing various forms of thyroiditis (e.g., Hashimoto's thyroiditis, subacute thyroiditis). - It identifies characteristic inflammatory cells, giant cells, and changes in follicular cells consistent with the diagnosis. *Medullary carcinoma thyroid* - Medullary thyroid carcinoma can be reliably diagnosed by FNAC due to its characteristic **polygonal or spindle-shaped cells**, **amyloid deposition**, and presence of **calcitonin** in the aspirate [2]. - Immunocytochemical staining for calcitonin further confirms the diagnosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1100-1101. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 429-430. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, p. 1099.