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Anaplastic thyroid carcinoma (ATC) is an aggressive thyroid malignancy with high mortality rate. This malignancy arises in thyroid follicular cells either denovo or with an associated differentiated thyroid carcinoma component. Clinically, it usually presents as a rapidly enlarging mass, pain and locally compressive symptoms. Histopathologic variability and heterogeneity often pose diagnostic challenges, especially in scant and paucicellular specimens. This article describes the clinical, histopathologic and molecular features of ATC and also addresses the associated diagnostic limitations and challenges.

The transcription factor Pax8 is already known to be essential at very early stages of mouse thyroid gland development, before the onset of thyroid hormone production. In this paper we show, using a conditional inactivation strategy, that the removal of the Pax8 protein late in gland development results in severe hypothyroidism, consequent to a reduced gland size and a deranged differentiation. These results demonstrate that Pax8 is also an essential player in controlling survival and differentiation of adult thyroid follicular cells. © 2014 Elsevier Ireland Ltd.

In order to assess morphological and functional plasticity of the thyroid gland in aging the effects of fasting and refeeding on the thyroid morphology and thyroid hormone serum levels were compared with morphometry and RIA in young and old rats. Young (4 months) and old (24 months) male Wistar rats were fasted for 40 h and sampled, or fasted and fed thereafter for 4 or 24 h. In control (fed) old animals the thyroid follicules were larger, the follicular epithelium was smaller and colloid resorption was smaller than in young rats. 'Thyroid activation index' (epithelial volume/colloid volume ratio) was almost twice lower in the thyroids of control old rats. As the result of fasting, height, surface area and volume of epithelial follicular cells decreased in the thyroids of fasted young rats but not in old ones. On the contrary, in thyroids of fasted old rats the dimensions of epithelial cells did not change and thyroid colloid resorption was increased. After 24 h of refeeding, thyroid morphology in both young and old rats did not differ significantly as compared with control animals. Upon fasting, serum levels of thyroxine (T4) and triiodothyronine (T3) decreased by 28 and 38% in young and by 35 and 46% in old rats, respectively. However, T4 and T3 serum concentrations did not differ significantly between age groups in both fed and fasted states. During refeeding the increase in serum thyroxine concentration was delayed in old rats as compared with young ones. The results of morphological, morphometric and hormonal investigations indicate the existence of age-related changes in the structure and function of thyroid follicular cells.

Biological similarities between dogs and humans make the dog an appropriate preclinical model for gene therapy of many human disorders. Retroviral and adenoviral vectors have been used to successfully transfer a variety of gene constructs to canine hematopoietic progenitor cells, fibroblasts, hepatocytes, thyroid follicular cells, and other cells. Canine hemophilia B and mucopolysaccaridosis I are currently being used as models for gene therapy of inherited diseases, and several other models are potentially available. Neoplastic diseases, including canine lymphoma, osteosarcoma, and melanoma are potential models for gene therapy of cancer. Cloned canine genes and reagents are becoming more available as models are developed. Collaborative efforts between basic scientists, physicians, and veterinarians, involving both academic and private sectors, will probably lead to significant advances in human gene therapy.

Summary The ultrastructure of experimentally induced thyroid follicular adenomas and carcinomas was studied in rats and hamsters by means of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Diaminobensidintetrachlorid (DAB) method was applied for cytochemical demonstration of the thyroid peroxydase activity. No significant difference was found in the ultrastructure between thyroid follicular adenomas and carcinomas in rats and hamsters. However, the ultrastructural organisation of tumor cells in carcinomas presuppose a more limited functional activity than in adenomas. The peroxydase activity of tumor cells was preserved, despite the presence of methylthiouracil (MTU) in the circulation. It was further noticed that malignant transformation of thyroid follicular cells does not lead to changes in the ultrastructural distribution of peroxydase activity. Scanning electron-microscopical examination of the thyroid tumors reveals significant changes in the structural organisation of tumor cells and follicles. The changes in the surface properties of thyroid gland in the course of malignant transformation should be considered as result of irregular cell proliferation, degenerative processes and functional heterogeneity of tumor cells.

Changes in the 3H-thymidine labeling index (LI), cell cycle time (TC) and growth fraction (GF) of the thyroid follicular cells were studied in 10 days old rats irradiated in the neck region with a single dose of 3 Gy X-rays. During the first 2 days after irradiation the number of proliferating follicular cells sharply increased, followed between the 2nd and 6th days by a phase of sharp decrease. Later, between the 10th and 16th days again an increase in the LI was observed. During the cell proliferation phase, the cell cycle was shortened from 79 hours in the control animals to 30.9 hours in irradiated animals. The GF was decreased from 40% in the former to 25% in the latter. S-phase duration (TS) was 1.6 hours longer in irradiated animals than in controls. The shortening of the cell cycle of irradiated animals is predominantly a result of diminishing G1-phase duration.

The action of thyrotropin on the rat thyroid follicular cell has been investigated using continuous transmembrane potential and input resistance recording from individual cells in in vitro preparations. The membrane potential in this study was −68.0 mV±0.6 (mean±S.E.). Over a wide range of concentrations (1.5–50 mU/ml), thyrotropin failed to affect membrane potential or input resistance while 20 mU/ml thyrotropin was shown to elicit complex time-dependent changes in tissue levels of both cyclic AMP and cyclic GMP. The present results reveal that thyrotropin-receptor interaction does not affect plasma membrane permeability, but is characterized by complex changes in endogenous cyclic nucleotide metabolism.

Microscopic concretions of barium and sulfur, mixed with natural radium were observed within the follicles of bovine thyroids from widely separated parts of the world. At least 80 per cent of bovine thyroids received from Nigeria, West Africa, and 60 per cent of those studied from Colorado, contained the radioactive concretions; their incidence has been less in other areas. The concretions probably consist of barium sulfate mixed with radium but the mechanisms for incorporation of these elements into thyroid follicles are unexplained. These radioactive bodies cause adjacent thyroid follicular cells to be exposed to relatively intense alpha radiation, but as yet, no biological effects have been ascribed to this radiation.