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Cytoplasmic colloid inclusions in thyroid lesions: a cytomorphological study based on fine needle aspiration
D K Das1, S K Pathan, I M Francis
1Pathology, Faculty of Medicine, Kuwait University, Safat, Kuwait. dilip76@hotmail.com
Insights
Intracytoplasmic colloid inclusions (CIs) are common in Hürthle cell neoplasms (HCN) and Hashimoto's thyroiditis (HT). These findings in FNA smears require careful interpretation to avoid misdiagnosis of HCN.
Area of Science:
- Thyroid pathology
- Cytopathology
- Surgical pathology
Background:
- Intracytoplasmic lumens (ICL) and magenta material are characteristic of Hürthle cell neoplasms (HCN).
- Intracytoplasmic colloid inclusions (CIs) were observed in Hürthle cells (HC) within a Hashimoto's thyroiditis (HT) case.
- The study aimed to determine the frequency and significance of CIs in various thyroid lesions.
Purpose of the Study:
- To investigate the prevalence of intracytoplasmic colloid inclusions (CIs) in Hürthle cells (HC) across different thyroid conditions.
- To differentiate the cytomorphologic features of Hashimoto's thyroiditis (HT) with and without CIs.
- To assess the diagnostic implications of CIs in fine-needle aspiration (FNA) smears.
Main Methods:
- Examination of FNA smears from 120 HT, 101 colloid goiters, 11 hyperplastic nodules (HN), and 76 neoplastic goiters.
- Identification and quantification of CIs and empty ICL in epithelial cells.
- Statistical comparison of CIs frequency and cytomorphologic features using Fisher's exact test.
Main Results:
- CIs were found in 30% of HT, 34.2% of neoplastic goiters, 27.3% of HN, and 4% of colloid goiters.
- HCN showed a significantly higher frequency of CIs (75.0%) compared to papillary thyroid carcinoma (33.3%) and follicular neoplasms (14.3%).
- CIs were more prevalent in HC in HT and HCN, but in follicular cells (FC) in other lesions. HT cases with CIs exhibited distinct cytomorphologic differences.
Conclusions:
- Hürthle cell metaplasia in HT may be a survival response of FC, with CIs indicating limited colloid synthesis capacity.
- Careful evaluation of FNA smears is crucial to distinguish HT with Hürthle cell changes and CIs, and papillary thyroid carcinoma with Hürthlization and CIs, from true HCN.
- The presence of CIs in Hürthle cells warrants consideration in the differential diagnosis of thyroid lesions.
Introduction:
Intracytoplasmic lumens (ICL) with or without magenta material and transgressing vessels are features of Hürthle cell neoplasms (HCN). After detection of intracytoplasmic colloid inclusions (CIs) including targetoid (magenta) body-like structures in the Hürthle cells (HC) in a case of Hashimoto's thyroiditis (HT), we reviewed cases of HT, thyroid neoplasms, hyperplastic nodules (HN) and colloid goitres to determine the frequency of these structures. Further, an attempt was made to find out the significance of CIs.
Methods:
FNA smears of 120 HT, 101 colloid goitres, 11 HN, and 76 neoplastic goitres were examined. The presence of CIs and empty ICL were noted in epithelial cells in these lesions. An attempt was made to find out the difference between HT with and without CIs in respect of various cytomorphologic features. The groups were compared using the Fisher's exact test of probability.
Results:
The CIs were present in 36 (30.0%) of HT, 26 (34.2%) of neoplastic goitres, 3 (27.3%) of HN, and 4 (4.0%) colloid goitres. As compared to colloid goitres, CIs were present in a significant higher number of cases in HN (P = 0.0202), neoplastic goitres (P < 0.0001), and HT (P < 0.0001). Among neoplasms the frequency of CIs in HCN (75.0%) was significantly higher than that of papillary thyroid carcinoma (PTC) (33.3%, P = 0.0466), and follicular neoplasm (14.3%, P = 0.0083). The CIs were more frequent in HC in HT and HCN but in follicular cells (FC) in other lesions. The HT cases with CIs differed significantly from those without CIs in respect of HC and their cellularity, cellularity of reactive lymphoid cells, extracellular colloid and empty ICL.
Conclusion:
Care should be taken not to diagnose HT cases with an excessive Hürthle cell component and CIs, and PTC cases with Hürthlization and CIs, as HCN in FNA smears. Based on review of the literature and our findings, it is suggested that the Hürthle cell metaplasia in HT is a survival response of FC and the presence of CIs in Hürthle cell may represent their limited ability to synthesize colloid.
