Relevance of rosette patterns in variants of papillary thyroid carcinoma

Abstract

Introduction: The detection of rosette-like clusters (RLC) of follicular cells in thyroid carcinoma has been reported mostly in the columnar cell variant of papillary thyroid carcinoma (PTC). Despite the fact that diagnosing variants of PTC is no longer encouraged by The Bethesda System for Reporting Thyroid Cytopathology, the identification of cytomorphological features such as RLC linked with these tumours might help reduce possible misinterpretation in thyroid fine needle aspiration (FNA) cytology. We accordingly investigated the potential correlation of architectural patterns including RLC with PTC variants. Methods: We analysed 225 thyroid FNA cytology cases diagnosed as suspicious for malignancy (SFM) and positive for malignancy (M) over a 1-year time where all samples had corresponding histology. We also included 150 benign lesions from the same period. The presence of RLC vs similar appearing solid clusters, papillary structures and microfollicles were evaluated. We also performed immunocytochemistry and molecular testing for BRAFV600E. Results: We included 100 (44.4%) SFM favouring PTC and 125 (55.6%) M cases with cyto-histological correlation. On histology, all SFM and M cases showed malignancy including 140 (62.2%) classic PTC and 85 (37.8%) PTC variants. The cytomorphological patterns in all FNA samples included solid (74%), papillary (89%), microfollicular (70%), and pseudo-RLC morphology (25.7%). We identified only pseudo-RLC in 33 FNA specimens from PTC variant cases that included tall cell variant (42.4%), hobnail variant (21.2%) and miscellaneous variants (36.3%) of PTC. No definitive RLC were detected in our series. Immunocytochemistry and BRAFV600E were not specifically linked with an RLC pattern. Conclusions: These findings demonstrate that in our dataset the architectural pattern of RLC was not recognised within PTC variants. However, we did identify a pseudo-RLC pattern that was observed in association with tall cell variant and hobnail variant cases of PTC.

FNA cytology of columnar cell variant of papillary thyroid carcinoma: A case report with review of literature

“…Our case also displayed large RLCs of columnar tumour cells, similar to the Ylagen et al and Sen et al studies 12,14 . In their study, Dell'Aquila et al concluded that the presence of an RLC architectural pattern is most likely to be associated with malignant thyroid lesions and is seen in aspiration cytology samples, not in histological samples 16 . The RLC pattern may be seen in the tall cell subtype, hobnail subtype, and CCVPTC 16,17 .…”

“…16 The RLC pattern may be seen in the tall cell subtype, hobnail subtype, and CCVPTC. 16,17 In situations of thyroid FNAC with an equivocal interpretation or little neoplastic component, the identification of the RLC architectural pattern paired with the typical nuclear and cellular features of conventional PTC may raise suspicion for aggressive PTC subtypes. A close cytological mimicker of CCVPTC is a tall cell subtype of papillary carcinoma (TCV-PC) composed of respiratory-like tall columnar cells with eccentric basally located nuclei, granular cytoplasm, and distinct cell borders resembling Hurthle cells, prominent intranuclear inclusions, and typical nuclear features of PTC; however, nuclear pseudostratification is absent.…”

“…12,14 In their study, Dell'Aquila et al concluded that the presence of an RLC architectural pattern is most likely to be associated with malignant thyroid lesions and is seen in aspiration cytology samples, not in histological samples. 16 The RLC pattern may be seen in the tall cell subtype, hobnail subtype, and CCVPTC. 16,17 In situations of thyroid FNAC with an equivocal interpretation or little neoplastic component, the identification of the RLC architectural pattern paired with the typical nuclear and cellular features of conventional PTC may raise suspicion for aggressive PTC subtypes.…”