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ABSTRACT Thyroid disorders can manifest in several forms, including follicular cell hyperplasia (goitre), follicular cell adenoma and follicular cell carcinoma. Following the detection of large and gradually increasing tumour‐like masses in the gular region of wild fourlined terapons (Pelates quadrilineatus) housed in various tanks in a public aquarium in June 2022, September 2022 and October 2023, several fish displaying clinical signs were transported to the Ornamental Fish Clinic at the Faculty of Veterinary Medicine, University of Tehran. Upon clinical inspection, the fish had prominent tumour‐like masses in the gular area, located beneath the operculum. Upon histological examination of the first series, the masses revealed thyroid well‐differentiated hyperplastic follicles that contained colloid and were lined by cuboidal epithelial cells. There were no signs of cellular atypia or mitotic figures. The study of the second series also revealed the existence of cellular atypia, but still no mitotic figures. In the examination of the third series, apart from the earlier lesions, there was evidence of neoplastic cell invasion into adjacent structures such as the adipose tissue and subepithelial layer. In addition, there was moderate cellular pleomorphism and a limited number of mitotic figures. Although the termination of water ozonation and the addition of potassium iodide to the feed were effective in treating thyroid hyperplasia, the treatment for thyroid neoplasia was not successful. The present study provides the evidence of clinical and histopathological findings of follicular cell hyperplasia, adenoma and adenocarcinoma of the thyroid gland in fourlined terapon. [ABSTRACT FROM AUTHOR]

Chlorine dioxide (ClO[sub 2]) is an effective drinking water disinfectant, but sodium chlorate (NaClO[sub 3]) has been identified as a potentially harmful disinfection by-product. Studies were performed to describe the development of thyroid lesions in animals exposed to NaClO[sub 3] in the drinking water. Male and female F344 rats and B6C3F[sub 1] mice were exposed to 0, 0.125, 0.25, 0.5, 1.0, or 2.0 g/L NaClO[sub 3] for 21 days. Additional male F344 rats were exposed to 0, 0.001, 0.01, 0.1, 1.0, or 2.0 g/L NaClO[sub 3] for 90 days. Female F344 rats were exposed to 0, 0.5, 1.0, 2.0, 4.0, or 6.0 g/L of NaClO[sub 3] for 105 days. Thyroid tissues were processed by routine methods for light microscopic examination, and follicular cell hyperplasia was diagnosed using a novel method. Thyroid hormone levels were altered significantly after 4 and 21 days. NaClO[sub 3] treatment induced a concentration-dependent increase in the incidence and severity of thyroid follicular cell hyperplasia. Male rats are more sensitive to the effects of NaClO[sub 3] treatment than females. Follicular cell hyperplasia was not present in male or female B6C3F[sub 1] mice. These data can be used to estimate the human health risk that would be associated with using ClO[sub 2], rather than chlorine, to disinfect drinking water. [ABSTRACT FROM AUTHOR]

BRAF exon 15 mutations are the most common molecular alterations found in papillary thyroid carcinoma (PTC). To date, there is no information regarding BRAF alterations in the thyroid parenchyma surrounding the tumor. To explore the early events associated with the development of PTC, we used massively parallel sequencing to investigate BRAF exon 15 in 30 PTCs and in 100 samples from the thyroid parenchyma surrounding the tumor. BRAF p.V600E was identified in 19/30 PTCs (63.3%). BRAF p.V600E mutations were identified in the tissue adjacent the PTC only in samples containing psammoma bodies. The other samples were either BRAF wild type (WT) or carried BRAF non p.V600E mutations. Specifically, BRAF p.G593D, -p.A598T, -p.V600M, -p.R603Q, -p.S607F, and -p.S607P were identified in 4 of 36 (11.1%) samples with follicular cell atypia, in 2 of 16 (12.5%) with follicular cell hyperplasia, and in 1 of 33 (3.0%) histologically normal samples—Only in tissue surrounding BRAF p.V600E mutated PTCs. These mutations are predicted to affect protein function in silico but, in vitro, have kinase activity and BRAF phosphorylation levels similar to BRAF WT. No BRAF exon 15 mutations were identified in samples adjacent to PTCs that were BRAF WT. A mutagenic process affecting BRAF exon 15 occurs in a subset of thyroid glands that develop BRAF p.V600E mutated PTCs. [ABSTRACT FROM AUTHOR]