Diagnostic clues indicating tall cell variants of papillary thyroid carcinoma in fine needle aspiration

Abstract

Background The definition of tall cell variant of papillary thyroid carcinoma (TCV‐PTC) depends on the articles, and the defined cytological findings characteristic of TCV‐PTC have not yet been fully analyzed. This study aimed to establish the cytological characteristics of TCV‐PTC. Methods We retrospectively analyzed the smears of 19 TCV‐PTC and 50 conventional PTC (C‐PTC) cases. Results Palisaded pattern with the nuclei locating at the base of tall columnar carcinoma cells was seen in 94.7% of TCV‐PTCs, and the incidence was significantly higher than that of C‐PTCs ( P < .0001). The palisaded pattern tended to appear at the periphery of the cell clusters. Isolated tall columnar carcinoma cells were present in 89.5% of TCV‐PTCs. The incidence was significantly higher than that of C‐PTC ( P = .0001). Tombstone appearance was identified in 78.9% of TCV‐PTCs, but not in C‐PTCs. Spindle‐like carcinoma cells with tapering cytoplasmic end appeared in 68.4% and 12.0% of TCV‐PTC and C‐PTC, respectively ( P < .0001). The cytoplasm of TCV‐PTC was densely stained and its cell border was distinct. Cytoplasmic elongation toward an outside of the cell clusters was observed in 89.5% of TCV‐PTCs. Conclusion It is the most important to identify the presence of the tall columnar carcinoma cells on the cytological preparations, in order to distinguish TCV‐PTC from C‐PTC. We propose five cytological findings indicating TCV‐PTC, (1) palisaded pattern, (2) tall columnar cells with the heights of at least three times their widths, (3) tombstone appearance, (4) spindle‐like carcinoma cells, and (5) cytoplasmic elongation.

Indications and Strategy for Active Surveillance of Adult Low-Risk Papillary Thyroid Microcarcinoma: Consensus Statements from the Japan Association of Endocrine Surgery Task Force on Management for Papillary Thyroid Microcarcinoma

“…Key point: Chest CT is not indicated at initiation of AS but may be indicated if there is disease progression. 20.9% in the 40s, 10.3% in the 50s, 8.2% in the 60s, and 3.5% in the 70s (34). Other studies have also demonstrated a lower rate of PTMC progression in older patients (15)(16)(17)35).…”

“…In addition, FNAC features suggestive of aggressive subtypes of PTC, such as tall cell variant, are recommended for immediate surgery, although direct evidence for this is lacking, and suspicion of such subtypes based on FNAC alone is not easy to diagnose in practice (20,21). Kuo et al investigated surgical cases of 18,260 conventional PTMCs and found 97 tall cell variant of PTMCs, and 90 diffuse sclerosing variant of PTMCs (22).…”

Active Surveillance as an Effective Management Option for Low-Risk Papillary Thyroid Microcarcinoma

“…Aggressive cytologic or histopathologic tumor characteristics have been demonstrated as contraindications to AS in previous studies [ 7 , 12 , 15 ]. Even though Tanaka et al [ 34 ] suggested five cytological findings indicating the tall-cell variant of PTC, the cytohistological findings might be different from final histologic findings because the proportion of tall columnar cells in the final histology is important for diagnosing the tall-cell variant of PTC. Furthermore, the cytohistological findings of other aggressive variants are not known.…”

Case for staged thyroidectomy

“…Classically for these tumors that are considered as "intermediate risk" according to the ATA, the option of a total thyroidectomy is generally retained. [29][30][31] In particular, the tall-cell variant of PTC is more likely to present with multifocal and bilateral disease, thus the indication becomes more compelling under such circumstances. 32 The removal of all thyroid tissue is justified for most tall-cell and other aggressive variants based on a higher likelihood for ETE.…”

“…However, such variants are more often diagnosed on histopathology. Classically for these tumors that are considered as “intermediate risk” according to the ATA, the option of a total thyroidectomy is generally retained 29‐31 . In particular, the tall‐cell variant of PTC is more likely to present with multifocal and bilateral disease, thus the indication becomes more compelling under such circumstances 32 .…”