Intrathyroid thymic carcinoma: A clinicopathological analysis of 22 cases.

OBJECTIVE: Intrathyroid thymic carcinoma (ITTC) is a rare malignancy. The current understanding of ITTC is inadequate, and there is no standard treatment for ITTC. In the present study, we aimed to explore the clinicopathological characteristics of ITTC and identify potential therapeutic targets. METHODS: The clinicopathological characteristics of 22 ITTC patients at our institution were reviewed. The expression of DNA mismatch repair (MMR) proteins and PD-L1 in ITTC were assessed by immunohistochemistry (IHC). RESULTS: All patients underwent surgery. There were nine females and 13 males, with a slight male predominance. Their ages ranged from 42 to 79 years (average, 54. 1 years). The diameters of the neck masses ranged from 10 to 100 mm (average, 39 mm). Ipsilateral lymph node (LN) dissection was performed in 18 patients: 12 demonstrated LN metastasis, six showed no LN metastasis, and no lymph nodes were dissected in four. One patient had liver metastasis. CK5/6, P63, CD5, and CD117 were expressed in all cases. All cases were negative for TTF1, PAX8, thyroglobulin, and BRAF V600E. DNA MMR protein expression was retained in all tested tumors, and EBV-encoded small RNA (EBER) in situ hybridization was consistently negative. The Ki67 proliferation index ranged from 10 to 70 %. All patients were followed-up for 14-134 months, four died, six were lost to follow-up, and the remaining patients survived without disease. The PD-L1 combined positive score ranged from 10 to 80 (average: 40). CONCLUSION: Our results confirm that CD5 and CD117 co-expression support a diagnosis of ITTC. All tumors in this cohort were DNA MMR-proficient and were not associated with Epstein-Barr virus (EBV) infection. A high CPS for PD-L1 suggests that immune checkpoint inhibitor therapy may be worthy of further exploration in patients with ITTC.

Clinicopathological features and outcomes of intrathyroidal thymic carcinoma: a single institution study.

Intrathyroidal thymic carcinoma (ITTC) is a rare malignancy of the thyroid. It is thought to originate from ectopic thymic tissue or embryonic thymic rest, in, or adjacent to, the thyroid. We analyzed the backgrounds, clinicopathological features, and prognosis of 20 patients with ITTC, treated at our hospital. Thirteen of the 15 patients (86%) who underwent ultrasonography were diagnosed as malignant, based on imaging findings. 16 of the 17 patients (93%) who underwent cytology, were diagnosed or suspected to be malignant. Locally curative surgery (thyroidectomy and lymph node dissection) was performed for 19 patients. Large tumor size (>4 cm) was positively related to pathological node metastasis (p = 0.0389). Fourteen patients, including nine Ex-positive patients, underwent adjuvant external beam radiotherapy (EBRT) of the neck after surgery. Two patients showed recurrence of thyroid bed after and neither of them underwent adjuvant EBRT after surgery. Two patients who underwent EBRT showed recurrences of the lateral nodes (level V and level II), but they were easily dissected by re-operation. Ten- and 20-year local recurrence-free survival rates were 84.9% and 60.6%, respectively. To date, four patients showed distant recurrence, and 10- and 20-year distant recurrence-free survival rates were 75.0% and 75.0%, respectively. Our findings indicate that 1) the prognosis of ITTC is generally favorable, and 2) large tumor size is significantly related to lymph node metastasis. Two patients showing recurrence of the central region did not undergo EBRT; thus, further comparative studies are desirable to elucidate whether EBRT can prevent significant local recurrence.

[Clinicopathological Features of Intrathyroid Thymic Carcinoma].

Objective To investigate the clinicopathological features,immunohistochemical characteristics,diagnosis,treatment and prognosis of intrathyroid thymic carcinoma.Methods Clinical data of 7 patients with intrathyroid thymic carcinoma were retrospectively reviewed.Histological examination and immunohistochemical staining were performed on the surgically resected tumors.The infection of Epstein-Barr virus(EBV)was detected by EBER in situ hybridization.Results The 7 patients included 5 males and 2 females.The age ranged from 40 to 71 years,with a median of 54 years.The tumors were located in the thyroid gland,with the maximum diameter ranging from 2.2 cm to 6.0 cm and the average maximum diameter of(4.0±1.2)cm.All the patients underwent thyroid gland resection and local lymph node dissection.After operation,all the cases were treated with radiotherapy and five of them additionally received chemotherapy.Six patients were followed up for 10-163 months,all of whom were still alive,including 2 patients with recurrence in situ,1 patient with homolateral cervical lymph node metastasis and the rest with no recurrence or metastasis.CK-pan,P63,CD5 and CD117 were expressed in all the cases,while TTF-1,TG,CT and PAX8 were negative.One case of them expressed SYN and CgA.Ki-67 proliferation index ranged from 10% to 90%.EBER in situ hybridization showed negative results in all 7 cases.Conclusions Intrathyroid thymic carcinoma is a relatively low-grade malignant tumor.The combination of immunohistochemical CD5,CD117 and monoclonal PAX8 is helpful in the diagnosis and differential diagnosis of intrathyroid thymic carcinoma.EBV may not be involved in the development of intrathyroid thymic carcinoma.Thyroid gland resection plus central lymph node dissection is an important treatment measure for intrathyroid thymic carcinoma.For patients with regional lymph node metastasis and obvious peripheral tissue invasion,postoperative radiotherapy with/without chemotherapy can effectively delay the disease progression.

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.

[A Case of Carcinoma Showing Thymus-Like Differentiation (CASTLE) of the Thyroid].

The case presented herein was a 70-year-old woman who had no compliant, but had a mass in the lower part of the right lobe of the thyroid detected by ultrasound (US). The US image of the tumor, measuring 13 mm in diameter, showed a low and heterogeneous internal echo level with calcification and an irregular margin. The tumor appeared to extend to the adjacent sternothyroid muscle, and cervical lymph node swelling was detected in a computer tomography (CT) image, but no metastatic lesion was found by positron emission tomography (PET)-CT. In a fine needle aspiration cytology of the tumor, papillary thyroid carcinoma was suggested because of the atypical epithelial cells having some changes other than intranuclear inclusion bodies. A subtotal thyroidectomy and central neck lymph node dissection were performed. The excised tumor was histologically composed of irregular nests or sheets of atypical squamoid epithelial cells with some ductal structures that leached to the sternothyroid muscle and involved the right lower parathyroid gland. Carcinoma showing thymus-like differentiation (CASTLE) was diagnosed histopathologically and immunohistochemically with the following immunohistochemical results: Cluster of differentiation 5 (CD5) (+), tumor protein p63 (p63) (+), KIT proto-oncogene receptor tyrosine kinase (c-KIT(CD117)) (+), thyroglobulin (-), and thyroid transcription factor-1 (TTF-1) (-). CASTLE is a rare carcinoma of the thyroid that architecturally resembles thymic epithelial tumors. Many CASTLE patients have been misdiagnosed as other carcinomas, such as anaplastic carcinoma, poorly differentiated carcinoma or squamous cell carcinoma of the thyroid. Immunohistochemical examination, including CD5 played an important role in the final diagnosis of CASTLE, although the distinction from diagnosis as squamous cell carcinoma or mucoepidermoid carcinoma in Hematoxylin-Eosin staining was challenging in our case. Nodal metastasis and perithyroidal tumor extension of CASTLE can predict its worse prognosis. Thus, at least careful follow-up studies are mandatory in cases of CASTLE.

Coexistence of intrathyroid thymic carcinoma and papillary thyroid carcinoma: a case report and literature review.

Background: Intrathyroid thymic carcinoma (ITTC) is a rare neoplasm of the thyroid, which accounts for less than 0.15% of all thyroid malignancies. The coexistence of ITTC and papillary thyroid carcinoma (PTC) is an extremely rare condition reported only in a limited number of cases. Case summary: A 26-year-old female presented with a growing neck mass, hoarseness, and dysphagia over four months. Ultrasonography revealed that the entire left lobe and the isthmus of the thyroid were replaced with a hypoechoic mass. Moreover, it revealed two hypoechoic nodules in the right thyroid. The patient underwent a total thyroidectomy and paratracheal lymph node dissection. Histopathological examinations revealed the coexistence of ITTC and PTC in the same thyroid. In immunohistochemical analyses, the ITTC was positive for CD5, P63, CD117, and CK 5/6 and negative for thyroglobulin, calcitonin, and TTF 1. At the same time, PTC was positive for TTF 1 and thyroglobulin and negative for CD5, P63, and CK 5/6. The patient received postoperative radiotherapy and remained well with no evidence of recurrence during one month follow-up. Conclusion: Distinguishing ITTC from other thyroid malignancies before the surgery is challenging due to its non-specific presentations. Therefore, the diagnosis relies on postoperative studies, especially immunohistochemistry. The recommended treatment approach to improve survival in ITTC cases is total thyroidectomy combined with cervical lymph node dissection, followed by postoperative radiotherapy. The coexistence of ITTC and PTC may indicate the similarity in the underlying mechanisms of these tumors. However, further investigations are needed to understand this potential correlation.

Intra thyroid thymic carcinoma: A case report and literature review.

INTRODUCTION AND IMPORTANCE: Intrathyroid thymic carcinoma (ITC) is a malignant epithelial tumor with thymic differentiation within the thyroid gland. Its frequency is up to 0.15 % of all malignant thyroid tumors. It is frequently a low-grade tumor. The clinical status is often misleading to other more advanced tumors like cervical lymph node metastasis of nonkeratinizing squamous cell carcinoma, undifferentiated variant, dedifferentiated carcinoma, and medullary carcinoma of the thyroid. CASE PREPARATION: The patient came to us with the diagnosis of cervical lymph node metastasis of undifferentiated carcinoma. This patient was first diagnosed with cervical lymph node metastasis in the previous hospital. After having an ITC diagnosis, the patient was operated on the rennet of thyroid glands and had a low dose of radio-chemotherapy for recurrent prevention purposes. It is the first case of such a disease diagnosed at our hospital and also the first case reported in Vietnam. CLINICAL DISCUSSION: ITC is rare and appears similar to all thymic carcinoma variants. The most popular type is squamous carcinoma. Immunohistochemical stains are typical for thymic origin tumors with CD5, CD117 positive. ITC is often negative for monoclonal PAX8 but positive in this case (MRQ-50 clone, Sigma-Aldrich). This finding is an exciting one that should considered. CONCLUSION: Reporting the case increases the awareness of the disease, especially among Vietnam Doctors and patients.

Intrathyroid thymic carcinoma: clinicopathological features and whole exome sequencing analysis.

Intrathyroid thymic carcinoma (ITC) is a rare malignant tumour. We present nine cases of ITC that were analysed by immunohistochemical staining, of which five were analysed using whole exome sequencing (WES). These cases included six women and three men with an age range of 31-66 years. The average postoperative follow-up term was 37.8 months (range, 7-95 months), and all patients survived well except for one case with lung metastasis. Microscopically, ITC showed solid islands of tumour cells separated by fibrous connective tissue containing lymphocytes and other inflammatory cells. Tumour cells strongly expressed Ckpan (AE1/AE3), P63, and CD117. And all cases but one were positive for CD5. The median value of Ki-67 was 32% (range 10-60%). We observed partial positivity of Syn and CgA in only one case. ITC shares morphological and immunohistochemical similarities with thymic squamous cell carcinoma. In situ hybridization of EBER showed negative results. All cases were microsatellite stable, and the tumour mutational burden of the 5 cases was all < 1 mutations/Mb. WES showed higher mutation rates for N4BP1 (2/5), and many genetic alterations were related to the NF-kB signalling pathway, which is crucial for insight into the molecular mechanisms of the occurrence and development of ITC.

Case report and literature review: thyroid carcinoma showing intrathyroid thymic carcinoma.

Background: Intrathyroid thymic carcinoma (ITTC) is a rare malignancy of the thyroid gland with histological and immunophenotypic resemblance to thymic carcinoma. Surgery combined with adjuvant radiotherapy improves the survival of patients with ITTC. However, for patients with extensive metastases, there is currently no effective treatment. Chemotherapy is an option but has not demonstrated improved patient survival. Methods and results: A female patient presented with metastases to the pleura, lung, and bone 16 years after surgery for ITTC. As radiotherapy and chemotherapy failed to control the recurrent disease, lenvatinib treatment was initiated. After 3 months, positron emission tomography/computed tomography showed a substantial reduction of all metastatic lesions and decreased tumor metabolism. The patient continues to receive lenvatinib and remains well and symptom-free. Conclusion: For patients with ITTC who have progressive, life-threatening metastases, lenvatinib represents a valuable salvage therapy that may offer a sustained reduction in tumor burden and maintenance of quality of life.

Genomic and immune microenvironment profiling in a case of metastatic intrathyroid thymic carcinoma.

Metastatic intrathyroid thymic carcinoma (ITTC) is a rare cancer with no effective drugs for controlling. This case report has shown genomic and immune microenvironment profiles in metastatic ITTC and emphasized an immunosuppression via a PD-1/PD-L1 pathway, possibly strengthening the rationale for immune checkpoint blockade as a novel treatment.

Identification of Recurrent TERT Promoter Mutations in Intrathyroid Thymic Carcinomas.

Intrathyroid thymic carcinoma (ITTC) is a rare malignant neoplasm considered to be a eutopic thymic carcinoma (TC) arising ectopically in the thyroid. Histopathologically, ITTC resembles squamous cell carcinoma of the thymus with positive TC markers such as CD5 and c-KIT. Despite these similar histological findings, ITTC is clinically less aggressive than TC. In this study, we compared clinical, histological, and genetic characteristics of ITTCs and TCs. We collected 9 ITTCs and 8 TCs with their clinicopathological profiles. Immunohistochemistry for CD5, p63, CD117/c-KIT, Ki-67, p53, TTF-1, thyroglobulin, PAX8, EGFR, and PD-L1/CD274 plus in situ hybridization for EBER was performed. We further investigated mutation status of KIT, EGFR, BRAF, and TERT promoter using Sanger sequencing. In our study, ITTCs affected significantly younger patients than TCs. After a mean follow-up of 86 months, all patients with ITTC were alive, while two patients with TC had died. Immunohistochemistry showed ITTCs and TCs had a similar immunophenotype except for EGFR and p53. Genetic analysis did not identify KIT or BRAF mutations in any ITTCs or TCs. EGFR mutations were positive in 11% (1/9) of ITTCs and 25% (2/8) of TCs. Notably, TERT promoter C228T mutation was identified in 22% (2/9) of ITTCs but none of the TCs. There were no significant differences in age, tumor size, or sex between TERT-mutated and TERT-wild-type ITTCs. Collectively, ITTC and TC have similar histopathologic and immunophenotypic features but different clinical outcomes. Recurrent TERT promoter mutation may be a key event related to cancer progression in ITTCs and warrants further investigation.

Clinicopathological Features of Intrathyroid Thymic Carcinoma / 中国医学科学院学报

Objective To investigate the clinicopathological features,immunohistochemical characteristics,diagnosis,treatment and prognosis of intrathyroid thymic carcinoma.Methods Clinical data of 7 patients with intrathyroid thymic carcinoma were retrospectively reviewed.Histological examination and immunohistochemical staining were performed on the surgically resected tumors.The infection of Epstein-Barr virus(EBV)was detected by EBER in situ hybridization.Results The 7 patients included 5 males and 2 females.The age ranged from 40 to 71 years,with a median of 54 years.The tumors were located in the thyroid gland,with the maximum diameter ranging from 2.2 cm to 6.0 cm and the average maximum diameter of(4.0±1.2)cm.All the patients underwent thyroid gland resection and local lymph node dissection.After operation,all the cases were treated with radiotherapy and five of them additionally received chemotherapy.Six patients were followed up for 10-163 months,all of whom were still alive,including 2 patients with recurrence in situ,1 patient with homolateral cervical lymph node metastasis and the rest with no recurrence or metastasis.CK-pan,P63,CD5 and CD117 were expressed in all the cases,while TTF-1,TG,CT and PAX8 were negative.One case of them expressed SYN and CgA.Ki-67 proliferation index ranged from 10% to 90%.EBER in situ hybridization showed negative results in all 7 cases.Conclusions Intrathyroid thymic carcinoma is a relatively low-grade malignant tumor.The combination of immunohistochemical CD5,CD117 and monoclonal PAX8 is helpful in the diagnosis and differential diagnosis of intrathyroid thymic carcinoma.EBV may not be involved in the development of intrathyroid thymic carcinoma.Thyroid gland resection plus central lymph node dissection is an important treatment measure for intrathyroid thymic carcinoma.For patients with regional lymph node metastasis and obvious peripheral tissue invasion,postoperative radiotherapy with/without chemotherapy can effectively delay the disease progression.

Ultrasonographic and clinical pathological features of intrathyroid thymic carcinoma / 中华超声影像学杂志

Objective To investigate the ultrasonographic and clinical pathological features of intrathyroid thymic carcinoma( IT TC) . Methods T he ultrasonographic and clinical pathological features of 11 cases of pathologically confirmed intrathyroid thymic carcinoma were analyzed retrospectively . T he size , shape ,boundary ,internal echo ,calcification ,cystic change ,blood flow of the lesion and lymph nodes of the neck were recorded . T I‐RADS classification was performed on the lesion ,and the medical history ,clinical symptoms and treatment process of the patients were recorded . Results T he lesions of all 11 patients were solid and located in the lower pole or middle‐lower part of the thyroid ,8 cases were located in the right lobe of the thyroid gland ( 8/11 ,72 .7% ) ,and 3 cases were located in the left lobe ( 3/8 ,27 .3% ) . T he maximum diameter diameter of the lesions was ( 3 .55 ± 0 .51 ) cm . All the lesions were hypoechogenicity or marked hypoechogenicity and ill‐defined margin . T he internal echo of the lesions were heterogeneous . Ten lesions were characterized by striped hyperechogenicity interiorly on ultrasonograms . According to T I‐RADS classification ,2 cases were class 4a ,3 cases were class 4b ,2 cases were class 4c and 4 cases were class 5 . T here was no cystic component or calcifcation in all lesions ,and there was no taller‐than‐wide shape . T hree of 11 cases were accompanied by Hashimoto′s thyroiditis . Postoperative pathology showed that 5 cases had cervical lymph node metastasis ,5 had perithyroidal soft tissue in ltration ,of them , 3 cases had recurrent laryngeal nerve ,2 cases invaded the esophageal wall ,and 3 cases invaded the striated muscle of the neck . Immunohistochemistry showed that CD5 and CD117 of all lesions were positive . All patients underwent surgery ,and 3 of them underwent radiotherapy and chemotherapy after surgery . Conclusions There are common sonographic features of intrathyroid thymic carcinoma ,which are located at the lower pole or middle‐lower of the thyroid gland ,presenting a solid hypoechogenicity or marked hypoechogenicity ,with ill‐defined margin and striped hyperechogenicity interiorly on ultrasonograms . T hese sonographic features are helpful for the diagnosis of IT TC .

Clinicopathological analysis of five cases of intrathyroid thymic carcinoma / 上海交通大学学报（医学版）

Objective: To investigate the clinicopathological features of intrathyroid thymic carcinoma. Methods: Clinical data of 5 patients with intrathyroid thymic carcinoma were retrospectively reviewed. Histological examination and immunohistochemical staining were performed on the surgically resected tumors. The infection of EB virus (EBV) was detected by in situ hybridization of EBV-encoded RNAs (EBER). BRAF V600E mutation was examined by amplification refractory mutation system. Results: There were 3 males and 2 females with age between 51 and 69 years (average of 60.8 years). All 5 cases were intrathyroid tumors. The tumors were 2.0-3.5 cm in diameter. All 5 cases showed positive staining for CK, CK19, P40, CD5, CD117, Bcl-2, and Ki-67 at protein level, and negative staining for other related differential diagnosis markers including 34βE12, TPO, TG, TTF1, SYN, EBV, and BRAF. In situ hybridization of EBER showed negative results and no BRAF V600E mutation was found. Conclusion: Intrathyroid thymic carcinoma is a low-grade malignant tumor. Expressions of CD5 and CD117 in tumor cells play a very important role in the differential diagnosis.