B-cell to T-cell ratio as a novel indicator in flow cytometry in the diagnosis of thyroid lymphoma.

Preoperative flow cytometry is recommended to prove the monoclonality and confirm the diagnosis of thyroid lymphoma. However, lymphoma cases without light chain restriction may also have monoclonality. The aim of our study was to identify a novel marker for thyroid lymphomas using aspirated materials for flow cytometry. We retrospectively analyzed 26 patients with primary thyroid lymphomas and 16 patients with benign lymphoproliferative lesions. The materials for flow cytometry were obtained by fine-needle aspiration cytology using a 22-gauge needle under ultrasound guidance. Light chain restriction was defined as a κ to λ ratio of less than 0.5 or more than 3.0. According to the light chain-positive rate, 25% or less and more than 25% were classified as the low and high light chain-positive rate groups, respectively. B-cell predominance was defined as a CD19 to CD4 ratio (B- to T-cell ratio) of more than 2.0. B-cell predominance was more frequently observed in lymphomas (88.5%) than in benign lymphoproliferative lesions (25.0%; p < 0.001). Light chain restriction based on the κ/λ ratio was detected in 69.2% of lymphomas, but not in benign lymphoproliferative lesions. Among lymphomas belonging to the low light chain-positive rate group, 88.9% did not exhibit light chain restriction and B-cell predominance was present. In contrast, benign lymphoproliferative lesions with B-cell predominance were not detected in the low light chain-positive rate group. B-cell predominance was a useful indicator for diagnosing thyroid lymphoma in the low light chain-positive rate group without light chain restriction.

Papillary Thyroid Carcinoma with Honeycomb-Like Growth: Clinicopathological Characteristics and Diagnostic Significance as a Novel Variant.

INTRODUCTION: We aimed to clarify the clinical and pathological characteristics of papillary thyroid carcinoma (PTC) with unique honeycomb-like growth (HLG) and discuss its diagnostic significance. METHODS: Among the 12,745 PTCs that were resected and histologically diagnosed, 28 PTC cases with HLG components (0.2%) were included. RESULTS: PTC-HLG was subclassified into pure (9 cases), which consisted of only HLG components, and mixed (19 cases), which consisted of conventional PTC and HLG components, types. HLG components were histologically characterized by (1) neoplastic cyst aggregation with intervening normal thyroid follicles, (2) the cyst wall composed of single-layered carcinoma cells, (3) low papillary growth, and (4) ball-like granulation tissues. Compared with the mixed type, the pure type occurred in older people (p < 0.05), had a smaller tumor size (p < 0.0001), was more interpreted as being benign by ultrasound (p < 0.05), and had a lower lymph node metastasis rate (p < 0.005). In the mixed type, 44.4% of conventional PTCs showed a Ki-67 labeling index of >5%. All and 10.5% of the mixed type showed lymph node and lung metastases, respectively. CONCLUSION: The pure type could be a nonaggressive variant of PTCs with a unique honeycomb growth pattern and tended to be clinically interpreted as benign. The mixed type is pathogenetically different from the pure type and is slightly aggressive compared with conventional PTCs.

Clinical significance and cytological detection of tracheal puncture following thyroid fine-needle aspiration: A retrospective study.

BACKGROUND: There have been no detailed reports on tracheal puncture after thyroid fine-needle aspiration (FNA). This study aimed to discuss the cytological differential diagnoses of tracheal puncture after thyroid FNA and clarify its clinical significance. METHODS: Tracheal puncture was defined as aspiration of tracheal components, including ciliated cells, chondrocytes, and goblet cells. A history of air suction or cough during aspiration was also considered tracheal puncture. Among the 18,480 nodules from 13,813 patients that underwent thyroid FNA, 70 (0.38%) nodules with tracheal puncture were retrospectively examined. Eleven thyroglossal duct cysts (TGDCs) and seven bronchial cysts that could exhibit ciliated cells were included in the study to compare the cytological findings. RESULTS: Sixty-six (94.3%) nodules had no clinical evidence of complications during and after FNA. Of the nodules with tracheal puncture, 64.3%, 48.6%, and 51.4% nodules were <1.0 cm in size, located in the isthmus, and associated with calcification. Cytological examination showed that chondrocytes and ciliated cells were present in 94.3% and 32.9% nodules, respectively. Ciliated cells seen in nodules with tracheal puncture and TGDCs were non-degenerative, whereas those in bronchial cysts were degenerative. CONCLUSION: Tracheal puncture after thyroid FNA is rarely noticed clinically, does not cause serious conditions, and spontaneously resolves. This complication more likely occurs in small-calcified nodules in the isthmus. Chondrocytes are more reliable diagnostic clues than ciliated cells to indicate tracheal puncture cytologically.

Evaluation of E-Cadherin and ß-Catenin Immunoreactivity for Determining Undifferentiated Cells in Anaplastic Thyroid Carcinoma.

INTRODUCTION: An immunohistochemical study has occasionally been performed to diagnose anaplastic thyroid carcinoma (ATC). However, antibodies to confirm the undifferentiated nature of ATC have not yet been evaluated. The aim of this study was to evaluate E-cadherin and ß-catenin expressions in immunoreactivity to determine undifferentiated carcinoma cells in the diagnosis of ATC. METHODS: We immunohistochemically examined 29 ATCs, 30 poorly differentiated thyroid carcinomas (PDTCs), 22 well-differentiated thyroid carcinomas (WDTCs), and 3 squamous cell carcinomas. Antibodies for thyroid transcription factor-1 (TTF-1), paired-box gene 8 (PAX8), ß-catenin, and E-cadherin were used. RESULTS: All WDTCs tested positive for TTF-1, PAX8, and E-cadherin. The positive rates of TTF-1, PAX8, and E-cadherin were 93.3, 93.3, and 100%, respectively, in PDTCs and 17.2, 51.7, and 10.3%, respectively, in ATCs. WDTC expressed the lateral cell membrane staining for ß-catenin and E-cadherin, whereas PDTC showed circumferential cell membranous expression (fishnet pattern). ß-catenin cell membrane expression in ATCs is lost or discontinuous. Carcinoma cells with ß-catenin nuclear expression without cell membranous expression were scattered in 72.4% of ATCs but were not observed in the other carcinomas. CONCLUSION: We propose 3 immunohistochemical findings to determine undifferentiated carcinoma cells in the diagnosis of ATC: (1) ß-catenin nuclear expression with no or reduced cell membranous expression, (2) the loss or discontinuous pattern of E-cadherin expression, and (3) the loss of PAX8 nuclear expression.

Potential role of mobile rapid on-site evaluation® in thyroid fine-needle aspiration cytology to reduce delayed repeated aspiration.

Rapid on-site evaluation of fine-needle aspiration cytology is time-consuming and requires specialized cytopathology staff. Mobile Rose® is a newly developed device for rapid on-site evaluation of fine-needle aspiration cytology. This study aimed to investigate the potential role of Mobile Rose® in reducing delayed repeated aspiration of the thyroid. A total of 120 cytological samples were collected and observed using Mobile Rose® after fine-needle aspiration cytology between September and October 2020, with immediate assessment of minimal or no cell clusters after conventional smear preparation. After qualifying and scoring, needle washout materials were prepared using the BD CytoRichTM method and correlated with cytology results. The average turn-around time of Mobile Rose® was found to be 1.5 minutes. Sensitivity, specificity, positive predictive value, and negative predictive value were 94.4%, 100%, 100%, and 57.1%, respectively. False-negative results were attributed to small aggregates of cells that were difficult to distinguish from the background and artifacts. Mobile Rose® may represent an important innovation for rapid on-site evaluation that is fast, has high diagnostic performance, does not require the presence of specialized cytology staff, and can reduce delayed repeated aspiration of the thyroid gland. However, further minor improvements and confirmation are required.

Histological alterations following fine-needle aspiration for parathyroid adenoma: Incidence and diagnostic problems.

This study aimed to clarify the histological alterations following fine-needle aspiration for parathyroid adenoma and discuss the occurrence of diagnostic problems. Among the 392 patients with parathyroid adenoma who underwent resection, fine-needle aspiration was performed for 21 (5.1%) parathyroid adenoma nodules. Histological findings that were significantly more frequent in cases that underwent fine-needle aspiration were considered histological alterations following fine-needle aspiration for parathyroid adenoma, including the following six findings: thick fibrous capsule (71.4%), multilayered fibrous capsules (14.3%), capsular pseudo-invasion (42.9%), fibrous bands (57.1%), hemosiderin deposition (14.3%), and tumor implantation (14.3%). Eighteen parathyroid adenoma nodules (85.7%) exhibited one or more of the six findings. Tumor cells and adipocytes entrapped within the thick fibrous capsule were occasionally observed. The fibrous bands were frequently connected to the thick fibrous capsule. The number of passes, duration between fine-needle aspiration and resection, tumor size, and purpose of fine-needle aspiration were not related to the incidence of histological findings. Because of the histological alterations following fine-needle aspiration for parathyroid adenoma that can be easily mistaken for signs of atypical adenoma or parathyroid carcinoma, we recommend that the six findings be excluded from pathological findings indicating atypical adenoma or parathyroid carcinoma in patients with preoperative fine-needle aspiration.

Fine-needle aspiration of parathyroid adenomas: Indications as a diagnostic approach.

BACKGROUND: We aimed to determine the indication of fine-needle aspiration (FNA) for parathyroid adenoma (PA)-suspected nodules and the cytological features of PA, and to discuss the ancillary techniques for diagnostic confirmation. METHOD: Clinical, cytological, and histological examinations of 15 PA patients (4.0% of all PA resected patients) were conducted through FNA on 16 nodules. We also examined the cytological preparations of 10 follicular neoplasms (FNs) and 10 poorly differentiated thyroid carcinomas (PDTCs). RESULTS: FNA was performed to detect PA in nine (56.3%) nodules. The remaining seven (43.8%) nodules underwent FNA for lesions considered as thyroid nodules or lymph nodes. The levels of parathyroid hormone (PTH) in the aspiration needle washout fluid were observably high, except for that from one nodule with unsatisfactory FNA. Cytologically, the incidences of wedge pattern (86.7%) and salt and pepper chromatin (86.7%) in PAs were significantly higher than in FNs and PDTCs. In contrast, the appearance of colloid globules and nuclear grooves was less frequent than that of FNs and PDTCs. GATA-3 expression was intense in all PAs that immunocytochemistry were performed. Histologically, capsular invasion and/or laceration, tumor seeding, granulation tissue, and fibrosis were observed. CONCLUSIONS: When PA localization is unusual or inconclusive despite extensive imaging, FNA may be performed. We asserted that wedge pattern, salt and pepper chromatin, and the absence of colloid globules and nuclear grooves are diagnostic cytological indicators of PA rather than of FN or PDTC. We recommend PTH measurements using needle washout fluid for PA-suspected nodules, and immunocytochemistry with the GATA-3 antibody for cytologically PA-suspected nodules.

The Japanese reporting system for thyroid aspiration cytology 2019 (JRSTAC2019).

We introduce the Japanese reporting system for thyroid aspiration cytology 2019 (JRSTAC2019) proposed by the Japan Association of Endocrine Surgery and the Japanese Society of Thyroid Pathology. Pathological classification and recommended clinical management for thyroid nodules in Japan are different from those described in the World Health Organization classification or the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC). Therefore, it was necessary to develop a reporting system adapted for Japan. JRSTAC2019 is a modified version of TBSRTC. Currently, JRSTAC2019 is widely used in Japan, although the details of the system have not been introduced in English. JRSTAC2019 comprises seven categories: (I) unsatisfactory, (II) cyst fluid, (III) benign, (IV) undetermined significance, (V) follicular neoplasm (FN), (VI) suspicious for malignancy (SFM), and (VII) malignant. "Cyst fluid" nodules are classified as an independent category, and "recommended management" is in the same category as "benign" nodules. Surgical resection for FN nodules is decided upon by considering several parameters, and the decision is made without performing gene analysis. Non-invasive follicular thyroid neoplasm with papillary-like nuclear features tends to be more often diagnosed as papillary carcinoma. The risk of malignancy of SFM in Japan is higher than that in Western countries, and resection rates of SFM and malignant tumors are lower owing to active surveillance for low-risk papillary microcarcinoma. We recommend that each country should develop its reporting system, suitable for its medical and social needs. However, it should be easily compatible with TBSRTC for the ease of academic data sharing.

Prevalence and diagnostic significance of noninvasive follicular thyroid neoplasm with papillary-like nuclear features among tumors previously diagnosed as follicular adenoma: a single-institutional study in Japan.

The incidence of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in papillary thyroid carcinoma (PTC) is significantly lower in Asian countries than Western countries; however, the difference remains unexplained. This study aimed to evaluate the incidence of NIFTP in tumors diagnosed as follicular adenoma (FA) in a Japanese institution and discuss the significance of NIFTP. In this study, 44 tumors were investigated, which were histologically diagnosed as FA at the Kuma Hospital in 2008. Of the 44 tumors, 13 (29.5%) were revised as NIFTP. In the remaining 31 tumors, the FA diagnosis was reconfirmed. On aspiration cytology, most of the NIFTPs were categorized into follicular neoplasm or suspicious for a follicular neoplasm. On histological examination, 9 (29.0%) of 31 FA nodules showed a nuclear score of 1. Twelve (92.3%) of 13 NIFTP nodules showed a nuclear score of 2, and the remaining nodule had a nuclear score of 3. No metastasis of FA or NIFTP was detected. There were no evidences of distant metastasis during follow-up. This is the first study to describe that NIFTP is more frequently included in tumors diagnosed as FA rather than PTC in Japan. As clinical management of FA and NIFTP is the same, in Japan, there is no reason to distinguish between FA and NIFTP. Conclusively, the necessity of using the disease entity "NIFTP" is not found in Japan.

Clinicopathological features of primary thyroid Burkitt's lymphoma: a systematic review and meta-analysis.

BACKGROUND: Primary thyroid Burkitt's lymphoma (BL) is an extremely rare and highly aggressive form of non-Hodgkin's lymphoma; only isolated case reports are available for patients with this disease. METHODS: We analyzed the clinicopathological features of thyroid BL by conducting a meta-analysis of 21 known patients (including ours) and compared them to those of extrathyroidal BL. RESULTS: There were 13 men and 8 women with a median age of 39.3 years (range, 6-75 years). The median follow-up was 46.5 months (range, 0.5-361 months). Six patients (28.6%) had stage I disease, 2 (9.5%) had stage II, 2 (9.5%) had stage III, and 11 (52.4%) had stage IV. Five of 7 tested patients with thyroid BL (71.4%) had histological evidence of underlying Hashimoto's thyroiditis. Ki-67 labeling indices exceeding 90% in all 19 patients tested (100%). Fluorescence in situ hybridization performed on 12 patient samples revealed that all (100%) had MYC rearrangement. Among the 16 patients for whom follow-up data were available, 4 died of disease-related causes. Kaplan-Meier analysis revealed that the 12- and 60-month overall survival rates for patients with thyroid BL were 87.5 and 70.7%, respectively. CONCLUSIONS: Ours was the largest study of thyroid BL and its detailed clinicopathological features to date. Thyroid BL is not associated with underlying Epstein-Barr virus infection but is closely linked to Hashimoto's thyroiditis; patients generally have good overall survival and respond well to intensive chemotherapy. The correct pathological diagnosis is essential for treatment selection and outcome improvement.

Risk of malignancy and clinical outcomes of cyst fluid only nodules in the thyroid based on ultrasound and aspiration cytology.

BACKGROUND: The number of extensive studies focusing on cyst fluid only (CFO) thyroid nodules is limited, and the risk of malignancy (ROM) in CFO nodules has not been well-established. Thus, the purpose of this study was to investigate CFO nodules using cytology and ultrasound. In addition, we sought to define the ROM and determine the recommended clinical management of CFO nodules. METHODS: We retrospectively reviewed cytological preparations of 678 nodules that were originally identified as CFO nodules, including conventional specimens in 209 nodules, liquid based cytology (LBC) specimens in 221 nodules, and both conventional and LBC specimens in 248 nodules. Ultrasound reports with representative photographs were also reviewed. RESULTS: Of the 678 CFO nodules, 214 (31.6%) were reclassified into other categories, including non-diagnostic/unsatisfactory (ND/UNS) except for CFO (n = 15), benign (n = 198), and malignant (n = 1). Conventional preparations (33.5%) were more frequently reclassified than LBC preparations (13.6%; P < .0001). Re-aspiration for diagnosis was performed for only one calcified nodule. The rates of surgical resection and malignancy were 3.0% and 0.2%, respectively. Based on American Thyroid Association guidelines and the Kuma Hospital ultrasound classification, worrisome sonographic features were identified in 5.8% and 0% of CFO nodules, respectively. CONCLUSION: We propose that CFO nodules should be classified as separate from ND/UNS nodules; they should be categorized as a subtype of benign nodules. However, it is essential that fine-needle aspiration cytology be performed under ultrasound-guided real-time visualization of needle placement in the target nodule in all cases.

Flow cytometric, gene rearrangement, and karyotypic analyses of 110 cases of primary thyroid lymphoma: a single-institutional experience in Japan.

Ancillary studies for primary nodal lymphomas have been well documented; however, studies of primary thyroid lymphoma (PTL) are limited. Here, we aimed to clarify the clinicopathological, flow cytometric, gene rearrangement, and karyotypic characteristics of PTL by investigation of a large series at a single institute. We performed flow cytometric, IgH rearrangement, and karyotypic analyses of 110 PTL tissues surgically resected at Kuma Hospital between January 2012 and April 2017. All PTLs were of B-cell origin, including mucosa-associated lymphoid tissue lymphoma (MALTL; 89 patients, 80.9%), diffuse large B-cell lymphoma (DLBCL; 18 patients, 16.4%), and follicular lymphoma (FL; three patients, 2.7%). In 96 (87.3%) patients, anti-thyroid antibodies were positive. For flow cytometry using aspirated and resected materials, light chain restriction was observed in 73.7% and 69.2% of examined cases, respectively. Heavy chain JH DNA rearrangement was observed in 65.4% of PTLs (58.1% of MALTL cases, 100% of DLBCL cases, and 100% of FL cases). Chromosomal abnormalities were detected in 49.0% of PTLs, and translocation was most frequently detected (24.0%), followed by addition (20.8%) and trisomy (18.8%). The most frequent (9.4%) karyotype was t(3;14)(q27;q32). Both FLs harbored t(14;18)(q32;q21), and the karyotype was not detected in patients with MALTL and DLBCL. The negative rate for all three examinations was 3.8%. We concluded that thyroid MALTL was cytogenetically different from that in other organs. Our results suggested that pre-operative flow cytometry analysis using aspirated materials was as reliable as that using resected materials.

Optimal needle size for thyroid fine needle aspiration cytology.

Concerning the needle size for thyroid fine needle aspiration cytology (FNAC), 25-27-gauge needles are generally used in Western countries. However, in Japan, the use of larger needles (21-22-gauge needles) is common. The aim of our study was to determine the optimal needle size for thyroid FNAC. We performed ultrasound-guided FNAC for 200 thyroid nodules in 200 patients using two different-sized needles (22 and 25 gauge). For each nodule, two passes with the different-sized needles were performed. The order of needle sizes was reversed for the second group of 100 nodules. The second aspiration was more painful than the first, regardless of the needle size. An association with more severe blood contamination was more frequently observed with the use of 22-gauge needles (32.0%) than with the use of 25-gauge needles (17.5%) and in the second aspiration (37.5%) than in the initial aspiration (12.0%). The initial aspiration samples were more cellular than the second aspiration samples. Regarding the unsatisfactory and malignancy detection rates, there was no statistical difference between the needles. In three of seven markedly calcified nodules, it was difficult to insert 25-gauge needles into the nodules. In terms of the diagnostic accuracy and pain, either needle size can be used. We recommend using 22-gauge needles for markedly calcified nodules because 25-gauge needles bend more easily in such cases. We demonstrated that the initial aspiration tended to obtain more cellular samples and to be less contaminated. Thus, the initial aspiration is more important and should be closely attended.

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

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.

Impact of the modification of the diagnostic criteria in the 2017 Bethesda System for Reporting Thyroid Cytopathology: a report of a single institution in Japan.

The Bethesda System for Reporting Thyroid Cytopathology has recently been revised in 2017 (TBSRTC 2017). This study aimed to evaluate the impact of modifying the diagnostic criteria in TBSRTC 2017 at a single institute. We retrospectively reviewed cytological specimens of 10,399 thyroid nodules submitted for thyroid fine-needle aspiration cytology. Among them, 56 atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) nodules, 16 suspicious for malignancy (SFM) nodules, and 8 malignant nodules were re-categorized into follicular neoplasm or suspicious for a follicular neoplasm (FN/SFN). The incidence of FN/SFN was increased by 0.8%, while that of AUS/FLUS, SFM, and malignant nodule was decreased by 0.5%, 0.2%, and 0.1%, respectively. In nine (60%) of the 15 nodules that were re-classified from AUS/FLUS to FN/SFN nodules and re-aspiration was performed, it was possible to judge whether they were benign or malignant. Of the 24 patients with FN/SFN nodules originally diagnosed with SFM or malignant, 16 were followed up without surgical resection. In conclusion, TBSRTC 2017 only caused minor changes in the incidence of each diagnostic category. TBSRTC 2017 was revised to avoid false positives owing to noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) that account for >10% of papillary thyroid carcinomas; however, it is not necessary in low frequency NIFTP institutes or countries. In Japan, we propose active surveillance as an accepted option for clinically managing AUS/FLUS, FN/SFN, SFM, or malignant nodules having favorable benign clinical findings or being part of the low-risk group.

Utility of monoclonal PAX8 antibody for distinguishing intrathyroid thymic carcinoma from follicular cell-derived thyroid carcinoma.

Follicular cell-derived thyroid carcinomas, including thyroid squamous cell carcinomas (SCCs) and anaplastic carcinomas, are immunoreactive for paired-box gene 8 (PAX8), while non-follicular cell-derived thyroid carcinomas stain negative for the PAX8 antibody. Intrathyroid thymic carcinoma (ITTC) arising from the intrathyroidal ectopic thymus exhibits moderate-to-strong nuclear reactivity for polyclonal PAX8. This is difficult to understand given that PAX8 is not associated with embryonic thymic development. We aimed to determine the diagnostic significance of monoclonal PAX8 antibody in distinguishing ITTCs from follicular cell-derived thyroid carcinomas. Ten ITTCs, 14 poorly differentiated thyroid carcinomas (PDTCs), 14 thyroid SCCs, 7 thymic tissue specimens, 7 thymomas, and 1 thymic carcinoma were analyzed using antibodies against polyclonal and monoclonal PAX8, thyroid transcription factor-1, p63, and CD5. Four ITTCs (40.0%) stained positive for polyclonal PAX8; none stained positive for monoclonal PAX8. All PDTCs and 92.9% of SCCs were immunoreactive for both polyclonal and monoclonal PAX8. All PDTCs, 46.2% of SCCs, and none of the ITTCs were immunoreactive for thyroid transcription factor-1. Eight ITTCs (80.0%), but none of the PDTCs and SCCs, were immunoreactive for CD5. We are the first to show that ITTCs stain negative for monoclonal PAX8. Monoclonal PAX8 is a more reliable marker than polyclonal PAX8 for determining follicular cell origin. We conclude that monoclonal PAX8 is a useful marker for distinguishing ITTCs from PDTCs and SCCs. Monoclonal PAX8 negativity is additional evidence in support of ITTCs not being follicular cell-derived thyroid carcinomas, but having a thymic origin.

Derivation of thyroid lymphoepithelial cysts from follicular cells.

The pathogenesis of thyroid lymphoepithelial cysts is controversial, and two hypotheses have been proposed, namely derivation from branchial-derived remnants or from squamous metaplasia of the follicular cells. The aim of this study was to clarify the pathogenesis of thyroid lymphoepithelial cysts. We performed pathological and immunohistochemical examination of 21 thyroid lymphoepithelial cysts, 13 non-neoplastic squamous metaplasia samples without thyroid carcinoma, 13 solid cell nests, and 14 lateral cervical cysts. On ultrasound, half of thyroid lymphoepithelial cysts were interpreted as calcified nodules regardless of no calcification. Thyroid lymphoepithelial cysts and squamous metaplasia tended to be located in the central and lower portions of the thyroid, while solid cell nests were located in the upper and central portions (p < 0.05). In 95.2% of patients with thyroid lymphoepithelial cysts and all patients with squamous metaplasia, lesions were histologically associated with chronic thyroiditis forming lymph follicles. Hashimoto's disease was serologically confirmed in 18 patients with lymphoepithelial cysts (85.7%) and 10 patients with squamous metaplasia (76.9%). Immunohistochemically, lymphoepithelial cysts showed nuclear positivity for PAX8, thyroid transcription factor 1, and p63. One lateral cervical cyst (7.1%) showed positive staining for PAX8, while solid cell nests were PAX8-negative. In three (14.3%) cases of thyroid lymphoepithelial cysts, squamous cells located on the superficial layer were focally and weakly positive for CEA. We concluded that thyroid lymphoepithelial cysts originate from follicular cells and are unrelated to solid cell nests and lateral cervical cysts arising from branchial-derived remnants.

Identification of Cytological Features Distinguishing Mucosa-Associated Lymphoid Tissue Lymphoma from Reactive Lymphoid Proliferation Using Thyroid Liquid-Based Cytology.

OBJECTIVE: To identify cytological differences between mucosa-associated lymphoid tissue lymphoma (MALT-L) and nonneoplastic lymphocytes using thyroid liquid-based cytology (LBC). STUDY DESIGN: We observed LBC and conventional specimens from 35 MALT-L cases, 3 diffuse large B-cell cell lymphoma (DLBCL) cases, and 44 prominent nonneoplastic lymphocytic infiltration cases. RESULTS: In MALT-L cases, the incidence of lymphoglandular bodies in the LBC specimens was lower than that in the conventional specimens (p < 0.001). Moreover, the nuclear sizes in LBC specimens were larger than those in conventional specimens. In 62.9% of the MALT-L and all DLBCL specimens, large nuclei were present in > 10% of the lymphoid cells in LBC specimens. Two cases with prominent nonneoplastic lymphocytic infiltration also exhibited these findings. In LBC specimens, swollen naked nuclei with less punctate chromatin patterns and thin nuclear margins were observed in 92.1% of lymphoma and 20.5% of prominent nonneoplastic lymphocytic infiltration. Elongated nuclei were significantly more apparent in thyroid lymphoma than in prominent nonneoplastic lymphocytic infiltration (p < 0.001), with a significantly higher incidence in LBC specimens than in conventional specimens (p < 0.001). CONCLUSIONS: Lymphoglandular bodies are not reliable markers for lymphoma diagnosis using LBC specimens. Large, swollen naked, and elongated nuclei are useful in distinguishing thyroid lymphoma from nonneoplastic lymphocytes in LBC specimens.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features: a single-institutional experience in Japan.

Noninvasive encapsulated follicular variant of papillary thyroid carcinoma (PTC) was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). To date, no studies on NIFTP have been reported in Japan. This study aimed to evaluate the clinical, cytological, and pathological findings of 54 cases of NIFTP from a single center in Japan, and compare them with those in the western countries. There were no significant differences in age, sex, or tumor size between patients with NIFTP and those with invasive encapsulated follicular variant -PTC. Ultrasound investigation showed a high suspicion lesion in 6.5% of NIFTP and 44.1% of invasive encapsulated follicular variant -PTC (p<0.001). On fine needle aspiration cytology, 75.7% of NIFTP cases were reported as suspicious for malignancy or malignant. Nuclear grooves and irregular-shaped nuclei were observed in 94.6% of cases of NIFTP. Pathologically, 27.8% cases of NIFTP and 13.0% cases of invasive encapsulated follicular variant -PTC had been originally diagnosed as macrofollicular variants of PTC. There were no NIFTP cases with nodal metastasis. We concluded that NIFTP should be renounced noninvasive encapsulated follicular variant -PTC, and should be considered as a malignant tumor with exceeding indolent behavior, and lobectomy alone should be satisfactory for the diagnosis and treatment.

Fine-needle aspiration cytology for medullary thyroid carcinoma: a single institutional experience in Japan.

Many cytological studies on medullary thyroid carcinoma (MTC) have been reported; however, such studies in large series of patients with MTC have not been performed. We investigated MTC at a single institution in Japan using fine-needle aspiration cytology (FNAC), and aimed to establish a preoperative diagnostic algorithm for MTC. FNAC was performed in 119 of 149 patients with MTC (79.9%) who ultimately underwent surgical resection. Moreover, 22 of 56 hereditary MTC (39.3%) were diagnosed preoperatively without FNAC by their high serum calcitonin levels or increased response to calcium stimulation (11 cases each), as well as RET mutation analysis. On FNAC, 76.5% of nodules were categorized as 'malignancy' or 'suspicious for malignancy'. The sensitivity and specificity of calcitonin measurement in aspiration needle wash-out fluid and in immunocytochemical staining for calcitonin were 96.3% and 92.3% respectively. We proposed an algorithm for preoperative diagnosis of MTC utilizing FNAC: When thyroid nodules are highly suspicious for MTC by their clinical and ultrasonographic features, serum calcitonin measurement with or without a calcium stimulation test is required. Furthermore, FNAC should be performed for patients who do not have those findings. When there is a possibility of MTC at the time of FNAC, calcitonin measurement using needle wash-out fluid is a reliable diagnostic tool. When MTC is suspected on cytological examination, immunocytochemical staining for calcitonin is useful for confirming MTC diagnosis.