MAML2 gene rearrangement occurs in all Warthin-like mucoepidermoid carcinoma: A reappraisal in a series of 29 cases.

Background: Warthin-like Mucoepidermoid carcinoma (MEC) is a new and rare morphological variant of MEC, with only a few case reports in the literature. The clinicopathological, molecular features and bio-behaviors of Warthin-like MEC has not been studied extensively. We reappraisal all Warthin-like MEC patients diagnosed and treated at our hospital. Methods: Patient characteristics including clinicopathological features, genetic aberrations, treatment, and prognostic information were assessed and evaluated. Results: Twenty-nine Warthin-like MEC patients were identified, 19 patients were female (65.5 %), and 10 were male (34.5 %). The patients' age varied widely from 8 to 68 years (mean 42.3 years). Genetic aberrations of MAML2 rearrangement were detected in all Warthin-like MEC patients, which suggesting this genetic event is the unique feature of Warthin-like MEC. Twenty-five patients (86.2 %) were assessed as having a low-stage disease (I/II), and four (13.8 %) as having high-clinical stage disease (III/IV). More than half of the patients (16/29) underwent only partial sialoadenectomy; 2 patients underwent extended sialoadenectomy, and 11 patients underwent extended sialoadenectomy with cervical lymph node dissection. After a median follow-up time of 73 months (5-128 months), Twenty-eight patients were alive without recurrence at the end of the follow-up period, one patient died 1 year after surgery due to lung metastasis. Conclusion: Our data suggested that most Warthin-like MEC exhibited mild clinicopathological course and less aggressive bio-behavior, and an aggressive bio-behavior seemed to be very rare. In addition, in the salivary gland, MAML2 rearrangement seems to be a unique molecular feature of salivary Warthin-like MEC.

Warthin-like variant of papillary thyroid carcinoma with lymph node metastases: a case report and review of the literature.

BACKGROUND: We present a rare case of thyroid lesion marked as the Warthin-like variant of papillary thyroid carcinoma (WLV-PTC) with lymph node metastases. A proper preoperative identification is difficult because of unspecific cytology features and common ultrasound characteristics of this malignant tumor. The long-term prognosis cannot be thoroughly described due to the scarcity of data. The purpose of the presentation is to show common characteristics and long-term survival rates of an uncommon variant of differentiated thyroid cancer (DTC). Therefore, the data represented in this article can make a significant contribution to future investigations. CASE PRESENTATION: A 40-year-old Ukrainian woman had a lesion in the thyroid gland, which was accidentally diagnosed during medical checkup. Ultrasound (US) features were similar to the common suspicious nodule. It had typical signs of suspicion for malignancy (TI-RADS-4) on the background of thyroiditis. A thorough investigation of the neck showed lymph nodes with nonspecific US features on both lateral compartments. Lymph nodes were hypoechoic, oval-shaped and 10 mm wide, with regular contours, low central vascularity, with preserving hilar fat, without cystic formation. The patient did not have any complaints or changes in the hormone status. No hereditary findings linked with cancer were discovered. The woman had been living for a long time in the country with a high level of insolation, which was atypical for the ordinary environment of the patient. Fine-needle aspiration (FNA) of the lesion was done and the Bethesda system 6 result was obtained. Total thyroidectomy with central lymph node dissection was accomplished. The histological conclusion was WLV-PTC on the background of lymphocytic infiltration of the gland with metastasis to the lymph nodes. The inpatient radioactive iodine (RAI) ablation (100 mCi) was subsequently performed. Hormone withdrawal was used followed by RAI. In one year after the surgery the level of thyroglobulin (Tg) was 0.2 ng/ml. Up to the present time the five-year follow-up has not demonstrated any signs of recurrence relying on a level of Tg (< 0.04 ng/ml), Tg antibodies (< 14 IU/ml), neck US without any structural disease. CONCLUSION: WLV-PTC resembles salivary gland tumors with similar histological features. This variant is not well known, but often associated with a stroma lymphocytic infiltration and a low risk of lymph node metastases. It is regarded that this rare subtype has similar long-term survival rates as classic papillary thyroid cancer (PTC).

Heterogeneity in PD-L1 expression in MAML2-rearranged mucoepidermoid carcinoma.

OBJECTIVE: Mucoepidermoid carcinoma (MEC) is a malignant tumor with diverse morphologies, some of which have poor prognostic indicators and others that challenge the grading system. This study investigated the expression of PD-L1 in different grades and phenotypes of MEC. METHODS: The present study was carried out on twenty-four archival formalin-fixed, paraffin-embedded blocks of salivary MEC. Fluorescence in situ hybridization was used to detect MAML2 rearrangement in MEC cases to be included. The studied cases were then subcategorized based on their grading and phenotype and immunohistochemically stained for PD-L1. RESULTS: PD-L1 expression in MEC varied, with some variants showing moderate to strong immunoexpression, while others did not express it at all. In the Warthin-like MEC, some tumors show high expression of PD-L1, while in the same pattern, a few cases showed low or no expression. Intraosseous MEC exhibited moderate PD-L1 expression. Sclerosing MEC featured lower PD-L1 expression, from weak to moderate. Oncocytic MEC displayed relatively low PD-L1 expression levels (weak to moderate). CONCLUSION: The histomorphologic features of MEC may predict clinicopathologic behavior, and subtyping MEC may pose a significant therapeutic value, particularly for intraosseous MECs and clear-cell MECs. PD-L1 expression is a good predictor of survival outcomes in MECs.

Warthin-like papillary renal cell carcinoma: A case report.

BACKGROUND: Warthin-like papillary renal cell carcinoma (WPRCC) has been described as a rare pathological subtype of papillary renal cell carcinoma in the 2022 World Health Organization Classification of the Urinary and Male Reproductive System. Herein we report a case of WPRCC in the left kidney. CASE SUMMARY: Physical examination of a previously healthy 47-year-old woman revealed a lump in her left kidney, 4.5 cm × 3.5 cm × 3.5 cm in size. Based on the clinical information, imaging data, histmorphological features, and immunohistochemistry results, the pathological diagnosis was WPRCC in left kidney. CONCLUSION: Resection of the mass in the left kidney was performed and her postoperative course was uneventful.

Warthin-like papillary carcinoma thyroid.

Solitary thyroid nodule should raise a suspicion of malignancy, which is very common in middle-aged females. Papillary carcinoma thyroid is the most common thyroid malignancy. Warthin-like papillary carcinoma is one of its rare variants. It has a frequent association with Hashimoto's thyroiditis. Here, we report a case of 43-year-old female who presented with swelling in the anterior aspect of neck for 1 month. Fine-needle aspiration cytology features were suggestive of papillary carcinoma thyroid and biopsy confirmed the diagnosis of Warthin-like papillary carcinoma thyroid. This variant is of great clinical and prognostic significance as it carries an excellent prognosis.

Warthin-like papillary thyroid carcinoma: a case report and comprehensive review of the literature.

Background: Papillary Thyroid Carcinoma (PTC) is the most frequent endocrine malignancy with a variety of histological presentations. Warthin-like Papillary Thyroid Carcinoma (WLPTC) is an uncommon neoplasm that is recognized as a distinct subtype of PTC in the WHO classification of thyroid tumors. In this report, we present a novel case of WLPTC in a female patient and provide an in-depth review of the available literature on its clinical, pathological, and therapeutic characteristics. Case presentation: A 27-year-old female patient was referred for neck swelling. Ultrasound showed two suspicious thyroid nodules leading to a thyroidectomy. She was diagnosed with intermediate-risk bifocal foci of classic PTC and WLPTC, arising from a background of chronic lymphocytic thyroiditis (CLT). This pT1b(m) N1b M0 malignancy was treated with adjuvant isotopic ablation and suppressive thyroxine therapy. The 1-year outcomes were favorable. Literature review: It covered articles published from 1995 to 2022, by searching PubMed and Google Scholar using specific terms. Out of 148 articles reviewed by two authors, 25 relevant articles were selected, including 13 case reports and 12 case series. The study included 150 cases of WLPTC. Data related to clinical presentation, imaging, histological features, management, and outcomes, were extracted. The mean age of diagnosis was 39 years, with a female predominance. The most common clinical presentation was neck swelling. Thyroid autoimmunity was positive in 71.6% of patients. Lymph node metastases were present in 28% of cases, with no reported distant metastases. Overall, the outcomes were favorable. Conclusion: WLPTC shares similar clinical and radiological presentations as classic PTC. The hallmark histological features of WLPTC are papillae lined with oncocytic tumor cells with papillary nuclear changes and lymphoid stroma. WLPTC is almost constantly associated with CLT. The management of WLPTC aligns with that of classic PTC with comparable stage and risk category, often resulting in favorable outcomes.

Warthin-like papillary carcinoma: Case report.

Warthin-like papillary thyroid carcinoma is a rare variant of papillary carcinoma with a very good prognosis. It is often associated with lymphocytic thyroiditis. Due to its typical histological picture resembling Warthin's salivary gland tumor, the histological diagnosis is not difficult, usually does not require an accompanying immunohistochemical examination and is based on the presence of nuclear features typical of papillary carcinoma and the presence of oncocytes in a background of rich lymphocyte infiltrate. The preoperative cytologic examination is challenging, as many other lesions may have a similar picture. Women are more likely to get affected. It appears a decade earlier than the classic variant. Clinically, it presents similarly to a conventional papillary carcinoma. In our case report, we would like to present the case of a 56-year-old woman with non-toxic multinodular goiter, in whom the presence of this rare variant of papillary carcinoma was revealed by histological examination.

Proceedings of the North American Society of Head and Neck Pathology, Los Angeles, CA, March 20, 2022: Emerging Entities in Salivary Gland Tumor Pathology.

Salivary gland tumor pathology is one of the most challenging areas in all head and neck surgical pathology. Compounding its inherent difficulty are numerous novel entities, variants and concepts, most of which have been based on recent molecular discoveries. This review will serve to update the practicing pathologist on a selected group of emerging entities in salivary gland tumor pathology.

Warthin-Like Mucoepidermoid Carcinoma: A Morphological Spectrum - A Report of 3 Cases with Histological and Cytological Findings and Review of the Literature.

BACKGROUND: Mucoepidermoid carcinoma (MEC) showing Warthin's tumor (WT)-like features is a low-grade malignancy which should be differentiated from WT. Morphological features may be distinctly different in each case, causing diagnostic difficulties. CASE PRESENTATION: Three cases were presented and discussed with their morphologies. All cases that presented with a mass in the parotid gland went to parotidectomy, and all had preoperative fine-needle aspirations (FNAs). Case 1 was a 16-year-old female; FNA was suggestive of WT and initially interpreted as WT histologically. Case 2 was a 27-year-old male; FNA was interpreted as noninformative due to the presence of cyst fluid only. Case 3 was a 53-year-old male and cytologically was found to be suspicious for MEC which contained squamous and goblet cells on a mucoid background. On histopathological examination, case 2 and case 3 were morphologically consistent with low-grade MEC with WT-like features. Prominent lymphoid stroma and the cystic pattern were the characters of these tumors. Case 1 had the classical WT appearance with some mucinous and squamous metaplasia which could only be interpreted as MEC after the detection of MAML2 rearrangement by FISH. The other 2 showed either focal or relatively diffuse usual low-grade MEC findings, and case 3 was also confirmed by MAML2 rearrangement. CONCLUSION: Cytological and histopathological features revealed a spectrum. Differentiating WT-like MECs from ordinary WTs may be challenging. On the one end of the spectrum, they may look very much like WT, and on the other end, even though usual MEC features are present, still, WT-like appearance may pose diagnostic difficulty. Showing MAML2 rearrangement in these cases is very helpful. The presence of mucinous and squamous cells in an otherwise WT-like looking tumor should be alarming for MEC, and if possible, each case should be analyzed for MAML2 rearrangement.

Warthin like Variant of Papillary Carcinoma Thyroid with BRAF Mutation.

Warthin like papillary carcinoma of thyroid (WLPTC) is a distinct entity and rare variant of papillary thyroid carcinoma (PTC). Here we report two cases of WLPTC with clinical, pathological and molecular characteristics.

Fine-needle aspiration cytology of Warthin-like mucoepidermoid carcinoma: A case report with cytological review.

Warthin-like mucoepidermoid carcinoma (MEC) is a novel and rare subtype of MEC and is characterized histopathologically by the presence of abundant lymphocytic infiltration and cystic changes. A small number of cytological reports of this MEC variant is currently available. The present study reported on the sixth cytological case of Warthin-like MEC, reviewed the cytological features of the tumour and discussed the cytological differential diagnosis. A 16-year-old Japanese female presented with a painful mass in the left parotid gland. Fine-needle aspiration for cytological examination of the parotid gland tumour was performed, followed by partial parotidectomy. Cytological examination revealed sheet-like and folded epithelial cell clusters in a mucinous background accompanying abundant lymphocytic infiltration. Epithelial clusters comprised round cells with mildly enlarged round to oval nuclei, polygonal cells with relatively rich cytoplasm and slightly enlarged round to oval nuclei. Certain polygonal cells contained intracytoplasmic mucin. Histopathological examination of the resected parotid gland tumour indicated multiple cystic lesions with abundant lymphocytic infiltration accompanying lymphoid follicle formation. The cysts were lined by intermediate cells with occasional mucinous cells. Fluorescence in situ hybridization using the surgically resected specimen indicated mastermind-like transcriptional coactivator 2 (MAML2) rearrangement, a characteristic of Warthin-like MEC. Consequently, the patient was diagnosed with Warthin-like MEC. The literature review revealed that the characteristic cytological features of Warthin-like MEC are the presence of intermediate cells and lack of oncocytic cells in the mucinous material under an abundant lymphocytic background. Clinicopathological features may help with a differential diagnosis, particularly from Warthin's tumour, and detection of MAML2 rearrangement is able to improve the accuracy of diagnosis.

Primary Warthin's-like adenocarcinoma of the lung: A clinicopathological, immunohistochemical, and molecular analysis of three cases.

Three cases of primary pulmonary adenocarcinoma with prominent lymphoid stroma and papillary features mimicking Warthin's tumor are presented. The patients are two women and one man ages 52, 62, and 74 years respectively. Clinically, the patients presented with non-specific symptoms of cough, dyspnea, and chest pain. Imaging showed the presence of an intrapulmonary mass in the right lower, right upper and left lower lobe. All patients underwent lobectomy. Histologically, the tumors were characterized by the presence of and oncocytic papillary growth pattern embedded in a lymphoid rich background. Immunohistochemical stains for TTF-1, keratin 7, and beta-catenin were positive in the epithelial component, while CD20 showed strong positive staining in the lymphoid component. In addition, CD4 and CD8 also showed positive staining in a ratio of 3-4:1, EBER was negative. Kras mutations with wild type EGFR were identified in one case. Clinical follow-up ranging from 8 to 24 months was obtained showing that all patients are alive without recurrence. The cases herein presented represent an unusual histological variant of primary lung adenocarcinoma, which closely mimics Warthin's tumor.

Thyroid Warthin-Like Cancer Concurrent With Multiple Sclerosis: A Case Report.

Warthin like-papillary thyroid cancer (WL-PTC) is a rare malignancy; it is difficult to distinguish preoperatively a WLPTC from a classic PTC. Often it is associated with Hashimoto thyroiditis (HT) that determines a better prognosis with a very low probability of recurrence. The case concerns a 43-year-old female with a single thyroid nodule suspected for cancer; and she had multiple sclerosis (MS) from the age of 19. Thyroid hormone levels were normal such as thyroid antibodies. Total thyroidectomy with lymphadenectomy of central compartment was performed. Histological examination revealed a Warthin like-PTC without Hashimoto thyroiditis. The mechanisms involved in pathogenesis of thyroid cancer in patients with autoimmune disease are not completely clear. We hypothesized that not only a local autoimmune response, such as HT, could contribute to the determination of this type of cancer but also a systemic autoimmune disease such as MS.

Warthin-like and classic papillary thyroid cancer have similar clinical presentation and prognosis.

OBJECTIVE: Warthin-like papillary thyroid cancer (WL-PTC) is an uncommon variant of PTC, usually associated with lymphocytic thyroiditis. Scarce evidence suggests that WL-PTC has similar clinical presentation to classic PTC (C-PTC), with no studies comparing risks of recurrence and response to treatment between both variants. Our objective was to describe the clinical presentation and prognosis of WL-PTC and compare it to C-PTC. METHODS: Retrospective analysis of a prospective cohort, including 370 (96%) patients with C-PTC and 17 (4%) with WL-PTC, consecutively treated with total thyroidectomy with or without RAI, followed for at least 6 months. We compared clinical presentation, risk of mortality and recurrence, as well as response to treatment between both variants. RESULTS: Of the total cohort: 317 (82%) female, 38 ± 13.5 years, median follow-up 4 years (0.5-28.5); most of them stage I and low/intermediate risk of recurrence. We found no differences regarding clinical-pathological data and risk of recurrence. WL-PTC was associated with a higher rate of anti-thyroglobulin antibodies (TgAb) (65% vs. 36%, p = 0.016) and lymphocytic thyroiditis (59% vs. 34%, p = 0.03). The rates of biochemical and structural incomplete responses were similar in both variants. WL-PTC had a lower rate of excellent response (23% vs. 54%, p = 0.01), which became non-significant when performing analysis by TgAb presence (50% vs. 67%, p = NS). CONCLUSION: WL-CPT and C-CPT have similar clinical presentation and rate of recurrence. The lower rate of excellent response to treatment in WL-PTC is due to a higher frequency of TgAb. WL-PCT should not be considered an aggressive variant of PTC.

Warthin-like variant of Papillary thyroid carcinoma-Case report of an uncommon tumour with review of literature.

BACKGROUND: Warthin-like variant of Papillary thyroid carcinoma (WLPTC) is an uncommon variant of PTC. They resemble Warthin tumour of salivary gland. Microscopically the tumour shows presence of papillae lined by oncocytic cells with typical nuclear features of PTC. The stalks of papillae were filled up with lymphoplasmacytic cells. WLPTC have good prognosis. CASE REPORT: A 45-year-old lady presented with thyromegaly. She underwent total thyroidectomy with bilateral selective neck dissection (level II - level VI). Her final histopathology report was WLPTC, Right lobe with lymph nodal metastasis. Post-operatively, she received I131 radio-iodine therapy. She is under follow-up for last four years and is doing well. CONCLUSION: Diagnosing WLPTC, a rare variant of PTC can be challenging. Definitive diagnosis helps in management.

Warthin-like and classic papillary thyroid cancer have similar clinical presentation and prognosis

ABSTRACT Objective Warthin-like papillary thyroid cancer (WL-PTC) is an uncommon variant of PTC, usually associated with lymphocytic thyroiditis. Scarce evidence suggests that WL-PTC has similar clinical presentation to classic PTC (C-PTC), with no studies comparing risks of recurrence and response to treatment between both variants. Our objective was to describe the clinical presentation and prognosis of WL-PTC and compare it to C-PTC. Subjects and methods Retrospective analysis of a prospective cohort, including 370 (96%) patients with C-PTC and 17 (4%) with WL-PTC, consecutively treated with total thyroidectomy with or without RAI, followed for at least 6 months. We compared clinical presentation, risk of mortality and recurrence, as well as response to treatment between both variants. Results Of the total cohort: 317 (82%) female, 38 ± 13.5 years, median follow-up 4 years (0.5-28.5); most of them stage I and low/intermediate risk of recurrence. We found no differences regarding clinical-pathological data and risk of recurrence. WL-PTC was associated with a higher rate of anti-thyroglobulin antibodies (TgAb) (65% vs. 36%, p = 0.016) and lymphocytic thyroiditis (59% vs. 34%, p = 0.03). The rates of biochemical and structural incomplete responses were similar in both variants. WL-PTC had a lower rate of excellent response (23% vs. 54%, p = 0.01), which became non-significant when performing analysis by TgAb presence (50% vs. 67%, p = NS). Conclusions WL-CPT and C-CPT have similar clinical presentation and rate of recurrence. The lower rate of excellent response to treatment in WL-PTC is due to a higher frequency of TgAb. WL-PCT should not be considered an aggressive variant of PTC.

The significance of mucinous metaplasia in Warthin tumor: a frequent occurrence and potential pitfall.

Mucinous metaplasia in Warthin tumor (WT) is a recognized phenomenon. Nevertheless, its presence can create a diagnostic challenge in the distinction from the newly proposed variant of mucoepidermoid carcinoma (MEC), Warthin-like MEC. In this study, we evaluated the significance and diagnostic relevance of mucinous metaplasia in WTs. A total of 30 WTs diagnosed based on resection specimens formed the basis of this retrospective study. Mucicarmine staining was performed to identify mucinous metaplasia, and fluorescence in situ hybridization (FISH) analysis was used to detect MAML2 gene rearrangement. After review, one MAML2 rearranged case was reclassified as Warthin-like MEC as the classic bilayered epithelium in WT was not identified. The diagnosis of WT was confirmed in the remaining 29 cases. Mucinous metaplasia was encountered in 24 WTs (83%), with 14% (4/29) having an abundant amount. We found that mucinous metaplasia correlated with tumor size (p < 0.05). Age and sex distribution were similar in WT cases with or without mucinous metaplasia. In addition, neither the presence of squamous metaplasia nor the time interval between fine-needle aspiration and surgery was related to mucinous metaplasia (p > 0.05). The MAML2 FISH analyses performed in 18 WTs with variable amounts of mucinous metaplasia were negative for rearrangement. In conclusion, mucinous metaplasia is fairly common in WTs and shows a significant correlation with tumor size. Therefore, caution should be taken to avoid overinterpretation of WT with mucinous metaplasia as MEC in cases showing the classic bilayered oncocytic lining epithelium.

Pediatric Warthin-like Mucoepidermoid Carcinoma: Report of Two Cases with One Persistent/Recurrent as Conventional Mucoepidermoid Carcinoma.

Mucoepidermoid carcinoma (MEC) is the most common primary salivary gland malignancy. While salivary gland neoplasia is rare in children, MEC is much more likely to occur in the pediatric population than Warthin tumor, a common benign salivary gland neoplasm associated with smoking and older age. The recently-reported Warthin-like variant of MEC bears a striking histologic resemblance to Warthin tumor, representing a potential diagnostic pitfall. Therefore, low-power observation of Warthin-like features in pediatric salivary gland tumors should prompt careful diagnostic consideration of Warthin-like MEC. Two cases of Warthin-like MEC in the parotid glands of teenaged patients were identified in the archives of the Department of Pathology at Children's Medical Center in Dallas, Texas. Surgical material for each case was reviewed and both diagnoses were verified. Fluorescence in situ hybridization (FISH) for CRTC1-MAML2 fusion was performed in both cases. Histologically, neither tumor exhibited the classic bilayer of oncocytic epithelial cells characteristic of Warthin tumor. Instead, the neoplastic epithelial cells exhibited architectural and cytologic atypia, with mucous cells interspersed. CRTC1-MAML2 gene fusions were identified via FISH and confirmed the diagnosis of MEC in both cases. Of note is that the second patient's tumor recurred with features of conventional MEC, indicating the potential for Warthin-like MEC to undergo this morphologic change. The present cases illustrate that Warthin-like MEC, like conventional MEC, may occur in the pediatric population. Pediatric and head and neck pathologists must be aware of this variant's existence and diagnostic criteria to avoid misdiagnosis as benign Warthin tumor.

MAML2 rearrangement as a useful diagnostic marker discriminating between Warthin tumour and Warthin-like mucoepidermoid carcinoma.

Warthin tumour is the second most common benign neoplasm of salivary glands. Despite its relatively characteristic histology, it may sometimes mimic other lesions. Here, we report two female non-smoker patients diagnosed with low-grade mucoepidermoid carcinoma with oncocytic epithelium and prominent lymphoid (Warthin-like) stroma and with molecularly confirmed MAML2 rearrangement. In addition, we screened a consecutive series of 114 Warthin tumour cases by means of MAML2 break apart fluorescence in situ hybridization to assess its value in differential diagnosis. MAML2 rearrangement was detected in both mucoepidermoid carcinoma cases, while all Warthin tumours were negative. Taking into account the literature data, Warthin-like mucoepidermoid carcinomas are more frequently observed in women, while a slight male predominance and smoking history are typical for Warthin tumour. In addition, the patients with Warthin-like mucoepidermoid carcinoma were significantly younger than those with Warthin tumour. To conclude, Warthin-like mucoepidermoid carcinoma may usually be suspected based on histology, while the diagnosis can be confirmed by means of molecular assays such as FISH. The investigation of MAML2 status is particularly advised when Warthin tumour is considered in a young, non-smoking, female patient.

Preoperative Cytologic Diagnosis of Warthin-like Variant of Papillary Thyroid Carcinoma.

BACKGROUND: Warthin-like variant of papillary thyroid carcinoma (WLV-PTC) is a relatively rare variant of papillary thyroid carcinoma with favorable prognosis. However, preoperative diagnosis using fine-needle aspiration (FNA) specimens is challenging especially with lymphocytic thyroiditis characterized by Hürthle cells and lymphocytic background. To determine a helpful cytological differential point, we compared WLV-PTC FNA findings with conventional papillary thyroid carcinoma with lymphocytic thyroiditis (PTC-LT) and conventional papillary thyroid carcinoma without lymphocytic thyroiditis (PTC) regarding infiltrating inflammatory cells and their distribution. Preoperative diagnosis or potential for WLV-PTC will be helpful for surgeons to decide the scope of operation. METHODS: Of the 8,179 patients treated for papillary thyroid carcinoma between January 2007 and December 2012, 16 patients (0.2%) were pathologically confirmed as WLV-PTC and four cases were available for cytologic review. For comparison, we randomly selected six PTC-LT cases and five PTC cases during the same period. The number of intratumoral and background lymphocytes, histiocytes, neutrophils, and the presence of giant cells were evaluated and compared using conventional smear and ThinPrep preparations. RESULTS: WLV-PTC showed extensive lymphocytic smear with incorporation of thyroid follicular tumor cell clusters and frequent histiocytes. WLV-PTC was associated with higher intratumoral and background lymphocytes and histiocytes compared with PTC-LT or PTC. The difference was more distinct in liquid-based cytology. CONCLUSIONS: The lymphocytic smear pattern and the number of inflammatory cells of WLV-PTC are different from those of PTC-LT or PTC and will be helpful for the differential diagnosis of WLV-PTC in preoperative FNA.