BACKGROUND: The most common of the aggressive variant of papillary thyroid carcinoma (PTC) is the tall cell variant (TCV). Because there are serious prognostic and management implications to a diagnosis of TCV, we review the entity to inform clinicians about the many facets of TCV. SUMMARY: The TCV of PTC is characterized by cells having the nuclear features of PTC and whose height is at least twice or thrice their width. There is disagreement regarding the proportion of tall cells and the cell height required to diagnose TCV. In view of its blurred definition and rarity, studies have shown that TCV is still underdiagnosed. We propose that PTC be diagnosed as TCV if it is composed of > or =50% tall cells. The latter should have a height that is at least twice their width, an eosinophilic cytoplasm, and the nuclear features of PTC. Whatever its definition, there is a consensus that TCV has a higher recurrence and death rate than classical PTC. Most authorities believe that TCV's worse prognosis is related to its older age at presentation, larger tumor size, and high frequency of extrathyroid extension (ETE). However, in a recent article, TCV without ETE was shown to have a more aggressive behavior than classical PTC without ETE independent of age, gender, and tumor size. The aggressive behavior of TCV could be related to the high expression of Muc1 and matrix metalloproteinase and to the higher prevalence of B-RAF mutations when compared to classical PTC. The importance of TCV is accentuated by the fact that it is overrepresented in those fluorodeoxyglucose positron-emission tomogram (FDG-PET)-positive thyroid carcinomas that are refractory to radioactive iodine (RAI) therapy constituting 20% of these incurable tumors. Conclusion: TCV is a biologically and clinically aggressive form of PTC that is still underdiagnosed. TCV is overrepresented in patients with RAI refractory disease. It has a high prevalence of B-RAF mutations making the latter an attractive target in RAI refractory cases. Imaging modalities that can detect RAI refractory disease such as FDG-PET scanning are needed in many patients and a requirement in those with extensive ETE. More studies are needed to identify those TCV that become RAI refractory and develop effective target therapies against these incurable carcinomas.
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"The tall cell variant of PTC, in contrast to CMV-PTC, shows an increased number of papillae composed of typical columnar cells with prominent double height in comparison with width and the frequent expression (80%) of RET/PTC and BRAF mutation . The columnar cell variant of PTC may show some overlap with CMV-PTC, especially in terms of pseudostratified columnar cells. "
"A consensus was reached when there was discrepancy between the observers. We excluded any cases with tumor necrosis or marked mitotic activity (≥3 mitoses/10 high power field, 400×) because these pathologic features themselves could be related to tumor aggressiveness.5,6,19,20 In cases with multiple tumor foci, the largest tumors were selected as the primary lesions. "
[Show abstract][Hide abstract] ABSTRACT: Background
The tall cell variant of papillary thyroid carcinoma (TCVPTC) is more aggressive than classic papillary thyroid carcinoma (PTC), but the percentage of tall cells needed to diagnose TCVPTC remains controversial. In addition, little is known about the clinicopathologic features of classic PTC with tall cell features (TCF).
We retrospectively selected and reviewed the clinicopathologic features and presence of the BRAF mutation in 203 cases of classic PTC, 149 cases of classic PTC with TCF, and 95 cases of TCVPTCs, which were defined as PTCs having <10%, 10-50%, and ≥50% tall cells, respectively.
TCVPTCs and classic PTCs with TCF did not vary significantly in clinicopathologic characteristics such as pathologic (p) T stage, extrathyroidal extension, pN stage, lateral lymph node metastasis, or BRAF mutations; however, these features differed significantly in TCVPTCs and classic PTCs with TCF in comparison to classic PTCs. Similar results were obtained in a subanalysis of patients with microcarcinomas (≤1.0 cm in size).
Classic PTCs with TCF showed a similar BRAF mutation rate and clinicopathologic features to TCVPTCs, but more aggressive characteristics than classic PTCs.
Full-text · Article · Jun 2014 · The Korean Journal of Pathology
"Limited experience exists about the role of FDG-PET or PET/CT in patients with more aggressive histological subtypes of DTC, including case reports or small case series in patients with tall cell , diffuse sclerosing   , solid/trabecular  and insular variant  of DTC. These articles underlines that FDG-PET or PET/CT seem to be very useful tools for the staging and restaging of such tumours. "
[Show abstract][Hide abstract] ABSTRACT: Aggressive histological subtypes of thyroid cancer are rare and have a poor prognosis. The most important aggressive subtypes of thyroid cancer are Hürthle cell carcinoma (HCTC) and anaplastic and poorly differentiated carcinoma (ATC and PDTC). The American Thyroid Association recently published guidelines for the management of patients with ATC, but no specific guidelines have been done about HCTC. We performed an overview of the literature about the role of Fluorine-18-Fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography (FDG-PET or PET/CT) in aggressive histological subtypes of thyroid cancer. Only few original studies about the role of FDG-PET or PET/CT in HCTC, PDTC, and ATC have been published in the literature. FDG-PET or PET/CT seems to be useful in staging or followup of invasive and metastatic HCTC. FDG-PET or PET/CT should be used in patients with ATC in initial staging and in the followup after surgery to evaluate metastatic disease. Some authors suggest the use of FDG-PET/CT in staging of PDTC, but more studies are needed to define the diagnostic use of FDG-PET/CT in this setting. Limited experience suggests the usefulness of FDG-PET or PET/CT in patients with more aggressive histological subtypes of DTC. However, DTC presenting as radioiodine refractory and FDG-PET positive should be considered aggressive tumours with poor prognosis.
Full-text · Article · Apr 2013 · International Journal of Endocrinology