Introduction: Thyroid fine-needle aspiration cytology (FNAC) has gained significance as a quick, safe, and relatively simple method to differentiate malignant from benign thyroid nodules and is regarded as the gold-standard first-line diagnostic test in the evaluation of thyroid nodules. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) established a standardized, category-based reporting system for thyroid FNAC with each category having an implied cancer risk. However, the optimal management of thyroid nodules in the Bethesda III and IV categories is controversial, given the variable malignancy rates. Aims/Objectives: (1) Analysis of the cytomorphological characteristics of patients with categories III and IV of “TBSRTC.” (2) Assessment of risk of malignancy of TBSRTC category III, IV, and substratification of TBSRTC category III. Materials and Methods: A retrospective and prospective study of cases categorized under TBSRTC as category III and IV at a tertiary-care center. Cytological along with their histological results were compared. Results: We identified an overall malignancy rate of 33% for nodules belonging to Bethesda category III and a malignancy rate between 19% and 33% for Bethesda category IV. Also, a significantly higher risk of malignancy in subcategories with nuclear and architectural atypia (66.6%) than only architectural atypia (28.7%). Conclusion: Although surgery is recommended in most of these cases, cytomorphology helps to predict the final histopathological findings with greater accuracy. Substratification of category III into subgroups may help reduce the heterogeneity of the atypia of undetermined significance/follicular lesion of undetermined significance category and more.

Risk of malignancy in thyroid nodules classified as Bethesda categories III, III - subcategories and IV: 2.5 years study

Context: Atypia of undetermined significance/Follicular lesion of undetermined significance [AUS/FLUS] is a heterogeneous category with a wide range of risk of malignancy [ROM] reported in the literature. The Bethesda system for reporting thyroid cytopathology [TBSRTC], 2017 has recommended subcategorization of AUS/FLUS. Aims: To evaluate the ROM in thyroid nodules categorized as AUS/FLUS, as well as separate ROM for each of the five subcategories. Settings and Design: Retrospective analytic study. Methods and Materials: A retrospective audit was conducted for all thyroid fine-needle aspiration cytology (FNAC) from January 2013 to December 2017. Slides for cases with follow-up histopathology were reviewed, classified into the five recommended subcategories, and differential ROM was calculated. Statistical Analysis Used: z test for comparison of proportions was done to evaluate the difference in ROM among different subcategories of AUS/FLUS. The P value of less than 0.05 was taken as statistically significant. Results: Total number of thyroid FNACs reported was 1,630, of which 122 were AUS/FLUS (7.5%). Histopathology was available in 49 cases, out of which 18 were malignant (ROM = 36.7%). The risk of malignancy (ROM) for nodules with architectural and cytologic atypia was higher (43.8%) than ROM for nodules with only architectural atypia (16.7%). Conclusions: The sub-classification of AUS/FLUS into subcategories as recommended by TBSRTC, 2017 may better stratify the malignancy risk and guide future management guidelines.

Risk of malignancy in Thyroid "Atypia of undetermined significance/Follicular lesion of undetermined significance" and its subcategories - A 5-year experience

Dilpreet Kaur

Papers

Risk of malignancy in Thyroid "Atypia of undetermined significance/Follicular lesion of undetermined significance" and its subcategories - A 5-year experience