Laser capture microdissection is a valuable tool in the preoperative molecular screening of follicular lesions of the thyroid: an institutional experience.

OBJECTIVES: The application of molecular tests to thyroid fine needle aspiration (FNA) has been shown to be a valuable tool to better refine the pre-operative malignant risk of patients with indeterminate cytology results. In this study, we investigated the feasibility of using the laser capture microdissection (LCM) technique to obtain DNA and RNA for molecular tests in routine thyroid FNA smears. METHODS: Nine coupled FNA and histological retrospective cases and 31 prospective FNA cases with a follicular neoplasm/suspicious for a follicular neoplasm (FN/SFN) diagnosis were included in this study. Both cytological and histological specimens were investigated by direct sequencing and reverse transcription-polymerase chain reaction (RT-PCR) for BRAF and RAS mutations and for PAX8/PPARG and RET/PTC rearrangements, respectively. RESULTS: LCM yielded good DNA and RNA quality in all cases (100%) in both series, irrespective of the staining used (Giemsa, Papanicolaou, immunostain for thyroglobulin) and the cytology technique (conventional or liquid-based preparations). Total mutations found in the FNA and in the corresponding histological specimen in both series were: one PAX8/PPARG rearrangement in a follicular carcinoma (FC), four NRAS mutations [in two FCs, one papillary carcinoma and one follicular adenoma (FA)] and one HRAS mutation in one FA. The sensitivity was 67% and the specificity was 91%. CONCLUSIONS: LCM is a valuable tool to obtain good quality DNA and RNA for molecular tests in cytological material from thyroid FNA, and can be a useful option in the management of patients with an FN/SFN FNA diagnosis.

A disproportionate accumulation of fibrous tissue is not a causal factor in human goitre growth.

Histological preparations from human nodular goitres reveal the presence of variable and sometimes considerable amounts of acellular material separating the individual follicles. Part of this interstitial tissue consists histologically of fibrous strands. However, quantitative data on the fibrous tissue content of goitres are scarce. In the present study the proportion of fibrous tissue in normal human thyroids and human goitres was determined biochemically by measuring their content of collagen, the predominant component of fibrous tissue. Total collagen content increased in parallel to thyroid weight. The relative collagen content, however, decreased slightly but significantly with increasing thyroid weight. The collagen/DNA ratio (= fibrous tissue/cell number ratio) was not higher in goitres than in normal human thyroids. These results indicate that in goitre growth, there is no disproportionate accumulation of fibrous tissue accompanying the multiplication of thyroid follicular cells. They are in line with the earlier findings that despite histological heterogeneity, the main component of nodular goitres is newly generated follicles.

The site of leakage of intrafollicular thyroglobulin into the blood stream in simple human goiter.

Serum thyroglobulin is increased in many thyroid diseases, including simple goiter. We followed thyroglobulin levels in 19 patients with diffuse and nodular euthyroid goiters by serial measurements of 80 samples over 2 yr. The large intraindividual variations suggested episodic release of thyroglobulin in this thyroid disease. To test the hypothesis that the phenomenon was due to sporadic release of colloid from diseased follicles, we studied 98 multinodular goiters by conventional histological techniques. Sixty-four surgical samples were auto-radiographed. Focal necrosis of single follicles as well as large necrotic areas, involving multiple follicles together with interstitial stroma, were found in 42% of the goiter specimens. The earliest stage of necrosis was focal death of epithelial cells, often followed by hemorrhages. Through the epithelial gaps, colloid leaked out into the interstitial space. In later stages, granulation tissue containing numerous macrophages invaded damaged follicles. Fibrous scars remained as ultimate witness of repair processes. In one chance observation, acute release of highly labeled thyroglobulin from follicular lumina into the interfollicular interstitium was autoradiographically documented. We conclude that the varying concentrations of thyroglobulin in serum of patients with simple goiter may result from episodic necrosis of follicles, permitting leakage of colloid into the interfollicular space.

[Autonomy and heterogeneity of the follicle in euthyroid and hyperthyroid human nodular goiter: answer to old riddles?]. / Autonomie und Heterogenität der Follikel in der euthyreoten und hyperthyreoten menschlichen Knotenstruma: die Lösung alter Rätsel?

The mechanisms responsible for the transformation of a morphologically and functionally normal thyroid into a heterogeneous eu- or hyperthyroid nodular goitre are summarized. The 3 basic processes of goitre pathogenesis are: 1. Each goitre develops from a normal thyroid gland by generation of new follicles. 2. New follicles are formed by multiplication of preferentially replicating cell clones of the follicular epithelium. Follicles already begin multiplying in response to a goitrogenic stimulus too weak to enhance metabolic functions other than replication. 3. The epithelial cells of normal follicles are not homogeneous and monoclonal, but belong to different populations with different metabolic equipment. Therefore, the daughter follicles may be metabolically different, e.g. in iodinating capacity. A certain degree of autonomous, i.e. TSH-dependent function is inborn to all follicles. The individual degree of autonomy of iodine turnover is not variable during goitrogenesis but determined by the metabolic individuality of the mother cell at the moment of folliculoneogenesis. These three basic processes explain the typical heterogeneity of nodular goitre. From autonomous highly iodinating cell families, autonomous "hot" daughter follicles arise which may be scattered all over the gland either as single follicles or as clusters of varying size (so-called "disseminated autonomy"). Particularly large clusters of "hot" follicles result in scintigraphically visible hot nodules, often called "toxic adenomas". Hyperthyroidism appears when the total joint autonomous hormone production of normal and "hot" follicles exceeds the requirements of the organism. The large majority of goitre nodules, including the so-called "toxic adenoma", are not true monoclonal benign neoplasias. Rather, they are built up by the same polyclonal heterogeneous follicles as extranodular goitre tissue. They have no choice but to expand in nodular fashion because they replicate within a poorly extensible network of connective tissue. This network of fibrous tissue results from scarring of multiple hemorrhagic necrosis occurring episodically during goitre growth.

Pathogenesis of thyroid nodules in multinodular goiter.

Pathogenesis of nodule formation was studied in over 100 nodular goiters from a subendemic area. 60 surgical specimens were autoradiographed. Only one classical, well-encapsulated adenoma was detected. All other nodules were incompletely encapsulated and consisted of follicles that were morphologically and functionally identical to those of nonnodular parenchyma. Most characteristic was the tremendous interfollicular heterogeneity appearing on autoradiographs. Nodular goiters contain multiple foci and strands of fibrous tissue, which result from scarring of multiple hemorrhagic necroses occurring during goiter growth. Therefore, the slowly growing number of newly formed follicles has to squeeze into the meshes of an inelastic network of connective tissue. Nodular growth pattern is the inevitable consequence. Some particular nodules expand because of excessive accumulation of colloid. We conclude that most thyroid nodules in long-standing goiters consist of ordinary, polyclonal goiter follicles which expand in nodular fashion because they replicate within a mold made out of a poorly extensible network of connective tissue.

[Treatment of hyperlipidemia type II with soybeans]. / Behandlung der Hyperlipidämie Typ II mit Sojabohnen.

15 outpatients with type II hyperlipoproteinemia (7 with type IIa and 8 with type IIb) were treated with soybean. This diet induced a significant decrease of plasma cholesterol levels from 314 +/- 24 to 267 +/- 30 mg/100 ml. Triglycerides levels remained unchanged. LDL-cholesterol decreased significantly from 241 +/- 26 to 194 +/- 32 mg/100 ml, whereas HDL-cholesterol increased only slightly and not significantly from 38 +/- 7 to 40 +/- 8 mg/100 ml. In our efforts to reduce hyperlipidemia the very low cost of these vegetable proteins is a further advantage. The hypocholesterolemic mechanism of soybean diet is unknown.