Tall cell variant of papillary thyroid carcinoma: Its characteristic features demonstrated by fine‐needle aspiration cytology and immunohistochemical study

Abstract

Tall cell variant (TCV) of papillary thyroid carcinoma is a rare tumor, which is usually associated with poor outcome, and pathologists often face the dilemma of proper diagnosis of TCV, not only by cytology but also histology. To allow surgeons to determine aggressiveness of the tumor before operation, it is important for pathologists to detect tall cell features correctly by fine-needle aspiration cytology (FNAC). However, the current criteria and definition of TCV are still controversial and confounded by another problem, the differential diagnosis from poorly differentiated thyroid carcinoma (PDC).In this report, we describe two cases of TCV and present characteristic FNAC findings. The tumor cells had a peculiar shape, which included tall, columnar, and oxyphilic cytoplasm with ''eccentric,'' basally located nuclei. We propose new terms for these cells, such as ''tail-like cells'' or ''tadpole cells. '' In the surgically-resected specimens, both cases exhibited remarkable extrathyroidal invasion accompanying prominent vascular invasions. They showed high Ki-67 (MIB-1) labeling index by immunohistochemistry, which indicated a higher proliferation activity of TCV than conventional form of papillary thyroid carcinoma.Furthermore, we discuss in this report the problematic issue of differential diagnosis of TCV from PDC and oxyphilic papillary thyroid carcinoma. Diagn. Cytopathol. 2009;37:732-737. ' 2009 Wiley-Liss, Inc.Key Words: thyroid; papillary carcinoma; tall cell variant; cytology; immunohistochemistry The tall cell variant (TCV) of papillary thyroid carcinoma has been recognized as a high-grade malignancy, which is usually associated with extrathyroidal invasion, vessel invasion, and local recurrence.1 It is an uncommon tumor, accounting for 1.3-12% of papillary thyroid carcinoma.1-11 Its disease-free 10-year survival rate is believed to be 10-15% lower than conventional form of papillary carcinoma (CPC). 2,3,5,6,11,12 By fine-needle aspiration cytology (FNAC) of the thyroid tumors, it is important to detect tall cell features before operation to predict aggressive clinical behavior. However, it is not so simple to make an accurate diagnosis of TCV by FNAC, because sometimes typical nuclear grooves and/or intracytoplasmic inclusions are not observed, while abundant oxyphilic cytoplasms are often shown. In addition, it is not uncommon that some cases of CPC include tall cell components to varying degrees. 13 Thus, during diagnosis of TCV by FNAC, special attention should be paid to the other types of histological variants of thyroid tumor or metastatic carcinoma from other organs as differential diagnoses.We report here two cases of TCV by FNAC, and describe their characteristic cytological features and histopathological findings. We also undertook an immunohistochemical study of these cases in this article. Materials and MethodsAspirates from the thyroid tumor of case 1 and from the lymph node of case 2 were studied. Each sample of alcohol-fixed smear was stained with Papanicolaou stain and air-dried s...

Can the Tall Cell Variant of Papillary Thyroid Carcinoma Be Distinguished from the Conventional Type in Fine Needle Aspirates? A Cytomorphologic Study with Assessment of Diagnostic Accuracy

“…While most cytopathologists are familiar with the features of cPTC, there are no widely accepted diagnostic criteria for TCV-PTC in FNAs [6,9,10,11,12,13,15,16,29,30,31,32]. Most authors report that compared to cPTC, TCV-PTC displays predominantly monolayer sheets with few papillary structures and rare psammoma bodies, relatively large cells with abundant oncocytic, finely granular cytoplasm and distinct cell borders, and prominent multiple INIs (‘soap bubble appearance').…”

“…The features of TCV-PTC have been described in the peer-reviewed literature, mainly in texts, case reports and small series [8,9,10,11,12,13,14,15,16,17]. However, unlike cPTC, the diagnostic criteria for TCV-PTC have not been clearly defined for FNA specimens.…”

Aggressive Variants of Papillary Thyroid Microcarcinoma Are Associated with Extrathyroidal Spread and Lymph-Node Metastases: A Population-Level Analysis

“…It accounts for approximately 2-6% of PTC, classically occurs in young women, and is reported to have increased rates of multifocality, bilaterality, extrathyroidal extension, recurrence, and nodal/distant metastasis (8)(9)(10)(11)(12)(13)(14)(15)(16)(17). TCV, first described in 1976, accounts for 3-12% of all PTC, and is characterized by a population of cells at least twice as tall as they are wide, comprising 30-70% of total tumor cells (8,(18)(19)(20)(21)(22). TCV has been reported to be larger than classic PTC on average, with higher rates of bilaterality, multifocality, extrathyroidal extension, recurrence, lymph-node/distant metastasis, and decreased survival (12,17,(23)(24)(25)(26)(27)(28)(29)(30).…”

“…Preoperative diagnosis of DSV and TCV is difficult (8,39). TCV and DSV have unique cytopathologic characteristics, and although diagnostic criteria have not been rigorously evaluated, several reports indicate that finding tadpole-shaped cells or inflammation and squamous metaplasia on FNA can raise preoperative suspicion of TCV or DSV (19,20,22,41,42). Nevertheless, preoperative diagnosis of variant histologies on fine needle aspiration (FNA) is limited, and it is more common for patients to be diagnosed postoperatively after histopathologic examination.…”

Classic Papillary Thyroid Carcinoma with Tall Cell Features and Tall Cell Variant Have Similar Clinicopathologic Features

“…The tall cell variant of PTC (TCVPTC) is the most common aggressive variant of PTC 2,3,4. The incidence of TCVPTC ranges from 4% to 17% of all PTCs, and its disease-free 10-year survival rate is believed to be 10% to 15% lower than that of classic PTC 5,6. The incidence of this disease in Korea has been reported to be up to 5%, although there are limited existing data 7,8.…”