What does the presence of numerous cohesive and micro-follicular groups of thyroid follicular epithelial cells in a thyroid Fine Needle Aspiration Cytology (FNAC) report indicate?

From the Research

The presence of numerous cohesive and micro-follicular groups of thyroid follicular epithelial cells in a thyroid Fine Needle Aspiration Cytology (FNAC) report typically indicates a follicular neoplasm, most commonly a follicular adenoma or potentially a follicular carcinoma. This cytological pattern represents a diagnostic challenge as FNAC cannot definitively distinguish between benign and malignant follicular lesions. The micro-follicular architecture shows small, crowded follicular cells arranged in three-dimensional clusters with minimal colloid, contrasting with the flat sheets and abundant colloid seen in normal thyroid tissue. This pattern occurs because follicular neoplasms tend to form small, tightly packed follicles with cellular crowding. When pathologists encounter this pattern, they usually classify it as "suspicious for follicular neoplasm" or "follicular lesion of undetermined significance" (FLUS/AUS) according to the Bethesda System. Some key points to consider in the diagnosis and management of such cases include:

• The importance of recognizing the micro-follicular pattern in thyroid FNAC, as highlighted in studies such as 1, which demonstrated the efficacy of follicular cell pattern analysis in thyroid FNAC evaluation.
• The need for surgical excision for definitive diagnosis, given that capsular or vascular invasion cannot be assessed on cytology alone, as discussed in 2 and 3.
• The risk of malignancy in these cases, which ranges from 15-30%, justifying the recommendation for surgical management, as noted in 4 and 3. Patients with these findings typically require surgical excision (lobectomy) for definitive diagnosis. Given the most recent and highest quality evidence, surgical management is recommended for patients with numerous cohesive and micro-follicular groups of thyroid follicular epithelial cells in their FNAC report, due to the potential risk of malignancy and the limitations of FNAC in distinguishing between benign and malignant follicular lesions, as supported by studies such as 4 and 1.