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Fine needle aspiration cytology of thyroid nodules: conventional vs thin layer technique
A Cavaliere1, R Colella, E Puxeddu
1Institute of Pathological Anatomy, Perugia University, Perugia, Italy.
Insights
Conventional smears are more sensitive for diagnosing thyroid cancer, while thin layer cytology reduces non-diagnostic cases. Combining both techniques is recommended for routine thyroid fine needle aspiration cytology.
Area of Science:
- Cytopathology
- Endocrinology
- Surgical Pathology
Background:
- Thin layer cytology is a newer method for thyroid fine needle aspiration (FNA).
- Its effectiveness compared to conventional smears is debated, with limited published data.
- This study aims to directly compare these two techniques in thyroid FNA.
Purpose of the Study:
- To compare diagnostic accuracy and efficiency of thin layer cytology versus conventional smears in thyroid FNA.
- To evaluate the rates of non-diagnostic samples and malignancy detection for both methods.
Main Methods:
- A prospective study involving 3875 thyroid nodules.
- Randomized, double cytologic sampling using both conventional and thin layer smear preparation.
- Cytohistologic correlation was performed for a subset of cases.
Main Results:
- Conventional smears showed higher sensitivity (93.6% vs 65.9%) and better cancer detection rates (44 vs 31 in cytohistologic correlation).
- Thin layer smears significantly reduced non-diagnostic cases (377 vs 541).
- Diagnosis agreement was 75.7%, with significant differences in malignancy and non-diagnostic rates.
Conclusions:
- Conventional smears are superior for diagnosing malignancy in thyroid FNA.
- Thin layer cytology effectively minimizes non-diagnostic sample rates.
- A combined approach using both techniques is suggested for optimal routine thyroid cytologic diagnosis.
Objective:
Liquid-based cytology using the thin layer technique has recently been introduced in thyroid fine needle aspiration cytology together with or in substitution of direct smears, but its usefulness is still controversial and relatively few studies have been published in this field. The aim of the present study was to compare the results obtained from conventional smears with those from thin layer smears.
Design:
In 3875 thyroid nodules, a double cytologic sampling was taken in randomized order, to prepare conventional or thin layer smears.
Main Outcome:
The diagnoses agreed in 2934 (75.7%) cases and disagreed in 941 (24.3%). The analysis of discordant data showed there were fewer non-diagnostic cases in the thin layer smears (377 vs 541, p<0.001) whereas in conventional smears there were more cases positive for carcinoma (27 vs 4, p<0.001). The cytohistologic correlation was available for 194 cases and showed that conventional smears had a greater capacity for revealing carcinomas (44 vs 31). Finally, diagnoses based on conventional smears were more sensitive than thin layer smears (93.6% vs 65.9%) whereas specificity was constant.
Conclusions:
From our experience, the conventional smear offers a greater possibility of diagnosis when suspecting malignancy or diagnosing malignancy cases, whereas thin layer smears significantly reduce the number of non-diagnostic cases. For this reason, we suggest combining the two techniques in routine cytologic diagnosis.
