Immunohistochemistry of thyroid gland carcinomas: clinical utility and diagnostic pitfalls

TERT accelerates BRAF mutant-induced thyroid cancer dedifferentiation and progression by regulating ribosome biogenesis

TERT reactivation occurs frequently in human malignancies, especially advanced cancers. However, in vivo functions of TERT reactivation in cancer progression and the underlying mechanism are not fully understood. In this study, we expressed TERT and/or active BRAF (BRAF V600E) specifically in mouse thyroid epithelium. While BRAF V600E alone induced papillary thyroid cancer (PTC), coexpression of BRAF V600E and TERT resulted in poorly differentiated thyroid carcinoma (PDTC). Spatial transcriptome analysis revealed that tumors from mice coexpressing BRAF V600E and TERT were highly heterogeneous, and cell dedifferentiation was positively correlated with ribosomal biogenesis. Mechanistically, TERT boosted ribosomal RNA (rRNA) expression and protein synthesis by interacting with multiple proteins involved in ribosomal biogenesis. Furthermore, we found that CX-5461, an rRNA transcription inhibitor, effectively blocked proliferation and induced redifferentiation of thyroid cancer. Thus, TERT promotes thyroid cancer progression by inducing cancer cell dedifferentiation, and ribosome inhibition represents a potential strategy to treat TERT-reactivated cancers.

Case Report: Next-Generation Sequencing Reveals Tumor Origin in a Female Patient With Brain Metastases

BACKGROUND

Brain metastasis mainly originates from lung cancer. Napsin A and TTF-1 factors have frequently been detected in lung adenocarcinoma cases. Brain metastasis tumors with napsin A and TTF-1 positive are easily classified as lung adenocarcinoma origin. However, some thyroid cancers also exhibit these clinical features. Besides, lung is the most common metastasis of undifferential thyroid cancer. Therefore, it requires development of novel diagnostic tools to aid in distinguishing between pulmonary and thyroid origin.

PATIENT FINDINGS

We reported a case that was initially diagnosed as brain metastatic lung cancer based on immunohistochemistry results. Analysis of next-generation sequencing (NGS) data from the brain lesion revealed that the cancer may have originated from the thyroid. We detected combo mutations in TERT promoter mutation, RET fusion and TP53, which are common in undifferential thyroid cancer (UTC), but rare for lung cancer. These results, coupled with identification of PAX8, indicated that this patient had UTC. Additionally, her three sons, despite being asymptomatic, were all diagnosed with papillary thyroid carcinoma.

SUMMARY

The patient received anlotinib treatment and showed good clinical outcomes. One month after anlotinib treatment, the pulmonary nodules were found to be controlled, and the thyroid tumor drastically reduced, and tracheal compression relieved. She continued anlotinib treatment for the following two months, but died one month later because the treatment stopped owing to financial reasons. All her sons underwent total thyroidectomy with lymph node dissection.

CONCLUSIONS

Although NGS has been reported to assist in diagnosis of the origin of some tumors, this is the first evidence of NGS for the determination of the origin of thyroid tumors. To our knowledge, this is the first time that a combination of multiple mutations has been used to help determine the origin of a tumor, compared with the previous single mutant gene. Moreover, this is the first evidence on the use of anlotinib for treatment of UTC with distant metastasis. Besides, all three sons of the patient had thyroid carcinoma in subsequent examinations, indicating high-risk for familial non-medullary thyroid cancer in UTC patients and necessity for performing thyroid ultrasound testing in other family members.

PAX8 expression in anaplastic thyroid carcinoma is less than those reported in early studies: a multi-institutional study of 182 cases using the monoclonal antibody MRQ-50

Anaplastic thyroid carcinoma (ATC) is an aggressive malignant tumor composed of undifferentiated thyroid follicular cells. Pathological diagnosis of ATC can be challenging as the tumor may show morphological overlap with other neoplasms with anaplastic morphology. Immunohistochemical demonstration of thyroid origin facilitates the diagnosis of ATC. Previous studies using the polyclonal anti-PAX8 antibody 10336-1-AP suggested that PAX8 was the most sensitive marker, expressed in up to 80% of ATC. According to a 2018 NordiQC report, the monoclonal anti-PAX8 antibody MRQ-50 has become the most commonly used anti-PAX8 antibody worldwide. However, validation of this antibody in ATC is lacking. In this study, we recruited 182 ATC cases from seven institutions. Pathology slides were subjected to histology review. PAX8 immunohistochemistry using the MRQ-50 antibody was performed in whole tissue slides (n = 147) or tissue microarray sections (n = 35). We found PAX8 expression in 54.4% of the cases, which was significantly lower than those reported in prior studies with the polyclonal antibody. PAX8 expression was positively correlated with the presence of an epithelial pattern (63.6% vs 37.5%, p = 0.0008) and a coexisting differentiated thyroid carcinoma component (71.6% vs 44.3%, p = 0.0004), but was not associated with age, gender, specimen type, or presence of giant cell and sarcomatoid patterns. In conclusion, we demonstrated PAX8 expression using the monoclonal antibody MRQ-50 in only half of the cases in a large ATC series. Pathologists should be aware that PAX8 expression in ATC is less than those reported in early studies to avoid misdiagnosis.

Development of a functional thyroid model based on an organoid culture system

The low turnover rate of thyroid follicular cells and the lack of a long-term thyroid cell culture system have hampered studies of thyroid carcinogenesis. We have now established a thyroid organoid culture system that supports thyroid cell proliferation in vitro. The established mouse thyroid organoids performed thyroid functions including thyroglobulin synthesis, iodide uptake, and the production and release of thyroid hormone. Furthermore, transplantation of the organoids into recipient mice resulted in the formation of normal thyroid-like tissue capable of iodide uptake and thyroglobulin production in vivo. Finally, forced expression of oncogenic NRAS (NRAS^Q61R) in thyroid organoids established from p53 knockout mice and transplantation of the manipulated organoids into mouse recipients generated a model of poorly differentiated thyroid cancer. Our findings suggest that this newly developed thyroid organoid culture system is a potential research tool for the study of thyroid physiology and pathology including thyroid cancer.

Elemental analysis of the thyroid by laser induced breakdown spectroscopy

The thyroid is an important hormone regulation organ. Laser induced breakdown spectroscopy (LIBS) is developed to assess iodine and other essential elements in the thyroid (of rats). Subjects are administered 0.05% iodine water for 0, 6, and 12 days before the thyroid is extracted. Pronounced iodine, sodium, calcium, and potassium emissions are observed at approximately 746, 589, 395/422, and 766/770 nm, respectively. Iodine emission is surprisingly highest in 0 day subjects, lowest after 6 days, and recovers by 12 days. This follows the Wolff-Chaikoff effect as ingestion of excess iodine reduces thyroid iodine and iodine is essential for hormone production. LIBS is a promising method for trace elemental analysis of the thyroid.