Thesis (MScMed (Dept. of Biomedical Sciences. Anatomy and Histology) --University of Stellenbosch, 2007. / Thyroid nodules are a common clinical problem encountered by physicians, surgeons and radiologists who deal with the head and neck region. However, most follicular lesions of the thyroid are benign, so that the indications for surgery should be as accurate as possible. The morphological difficulty on fine-needle aspiration biopsy (FNAB) of reliably distinguishing preoperatively between benign and malignant lesions has led to a search for ancillary methods that can assist with the diagnosis. The aim of the first study was to develop a cytological scoring system to improve diagnostic accuracy of fine-needle aspiration biopsy of papillary carcinomas with special reference to the follicular variant of papillary carcinoma. The objective of the second study was the application of immunodiagnostic markers Galectin-3 and HBME-1 to histology tissue sections and their corresponding fine-needle aspiration cytology smears to assess their value in distinguishing benign from malignant thyroid lesions. In the first study 16 different cytological features such as background, architecture and cellular morphology were quantatively assessed and scored. Only 14 of the 16 variables were statistically significant. The statistical analysis demonstrated that a score ≥ 4 was indicative of a papillary carcinoma with a sensitivity of 96%. A score < 4 suggested a benign multinodular goiter with a specificity of 97%. In the second study Galectin-3 and HBME-1 were applied to histology tissue sections and their corresponding fine-needle aspiration cytology smears. Statistical analyses showed that the sensitivity of immunohistochemistry for diagnosing malignancy was better than the immunocytochemistry, but the specificity of immunocytochemistry was superior. Furthermore the diagnostic accuracy of immunohistochemistry (86%) and immunocytochemistry (88%) using co-expression of these two antibodies was excellent. In this study on immunocytochemistry, papillary carcinomas were clearly identified with a 100% co-expression in the classic and 71% in the follicular variant of papillary carcinoma. For the surgeon the identification of papillary carcinoma is critical, as this determines the extent of surgery. Similary, the confirmation of a non-neoplastic lesion may prevent surgery. In most cases follicular neoplasms, benign or malignant, will usually be excised for histopathology, prior to definite therapy. These studies show that the implementation of ancillary methods such as a scoring system and immunodiagnostic markers can improve the diagnostic accuracy of thyroid fine-needle aspiration biopsies in our laboratory. This may lead to better management of thyroid nodules. However, it is advisable that cytopathologists always take all the clinical features and image analyses into consideration before making a diagnosis.

INTRODUÇÃO: Cerca de 80% dos nódulos de tireóide com citologia indeterminada são benignos. É possível que a tomografia por emissão de pósitrons (PET) com 2-[18F]- fluoro-2-desoxi-D-glicose (FDG) ajude a identificar quais dessas lesões são malignas. A captação de FDG depende da expressão de GLUTs (transportadores de glicose transmembrana) e hexoquinases. Captação difusa de FDG no leito tireoidiano tem ainda sido associada à tireoidite autoimune crônica (TAC), embora haja evidências de que pacientes com parênquima tireoidiano aparentemente sadio possam ter essa alteração. OBJETIVOS: (1) Determinar a sensibilidade e especificidade da PET-FDG no diagnóstico pré-operatório de malignidade dos nódulos tireoidianos, especialmente daqueles com resultados citológicos indeterminados, e avaliar esse desempenho no subgrupo de pacientes com TAC. (2) Determinar a correlação entre o achado de captação difusa tireoidiana da FDG à PET com o diagnóstico histopatológico de TAC e compará-la às concentrações plasmáticas dos anticorpos antitireoidianos. (3) Determinar a correlação entre a expressão dos marcadores imuno-histoquímicos GLUT 1, GLUT 3, GLUT 12, hexoquinase 2 e hexoquinase 3 com o diagnóstico histopatológico dos nódulos e com a captação de FDG apresentada pelos mesmos. MÉTODOS: 56 pacientes com nódulo de tireóide (42 com citologia indeterminada, 10 compatíveis com carcinoma papilífero e 4 com citologia benigna) realizaram PET-FDG e foram submetidos à tireoidectomia. Os resultados da PET-FDG foram comparados com o diagnóstico histopatológico do nódulo, com o infiltrado linfocitário no parênquima tireoidiano, com o diagnóstico de TAC e com os resultados do estudo imuno-histoquímico de micromatriz tecidual de tecido correspondente ao nódulo tireoidiano puncionado e ao tecido tireoidiano não nodular. RESULTADOS: 1) Todos os 21 pacientes com câncer de tireóide (11 com citologia indeterminada) apresentaram captação focal de FDG na tireóide. 2) Captação focal de FDG correlacionou-se com maior risco de malignidade (p<0,001). 3) Dos 31 pacientes com nódulos benignos com citologia indeterminada, 12 não tinham captação focal de FDG (especificidade de 39%). 4) Captação difusa no leito tireoidiano à PET-FDG foi associada à presença de TAC no exame histopatológico (p=0,019). Porém, 5 pacientes, sem sinais de infiltrado linfocitário, apresentaram captação difusa à PET-FDG. 5) Imunoexpressão dos anticorpos contra GLUTs 1, 3 e 12 e hexoquinases 2 e 3 nas células epiteliais dos nódulos não esteve positivamente associada com captação de FDG e com malignidade. 6) Não houve associação entre captação difusa de FDG no leito tireoidiano e imunoexpressão desses marcadores no parênquima tireoidiano não nodular. CONCLUSÕES: 1) A PET-FDG tem alta sensibilidade para diagnóstico de lesões malignas de tireóide, com especificidade de 39% para nódulos com citologia indeterminada. 2) Captação difusa de FDG no leito tireoidiano está associada à presença de TAC, mas pode ocorrer em pacientes sem infiltrado linfocitário. 3) A imuno-histoquímica para os anticorpos contra GLUTs 1, 3 e 12 e hexoquinases 2 e 3 não contribui para a diferenciação de nódulos malignos dos benignos e não se associa com a captação de FDG pelos nódulos / INTRODUCTION: Around 80% of thyroid nodules with indeterminate cytological result are benign. Positron emission tomography (PET) with 2-[18F]-fluoro-2-deoxy- D-glucose (FDG) might help to identify malignant thyroid lesions. FDG uptake depends on GLUTs expression (transmembranous glucose transporters) and on hexokinases. Although diffuse FDG thyroid uptake has been associated with chronic autoimmune thyroiditis (CAT), there is some evidence that patients with apparently normal thyroid parenchyma can display this pattern of FDG uptake. OBJECTIVES: (1) To assess the sensitivity and specificity of FDG PET in identifying thyroid malignancy in the preoperative evaluation of thyroid nodules and evaluate these results in the subgroup of patients with indeterminate cytological results and in the subgroup with CAT. (2) To compare the finding of diffuse FDG thyroid uptake with the histopathologic diagnosis of CAT and with the serum levels of antithyroid antibodies. (3) To evaluate the immunoexpression by thyroid nodules of GLUT 1, GLUT 3, GLUT 12, hexokinase 2 and hexokinase 3 and to compare it with the histopathologic diagnosis of these nodules and with FDG uptake. METHODS: 56 patients with thyroid nodules (42 with indeterminate cytological result, 10 with papillary carcinoma and 4 with benign cytological result) underwent FDG PET and, subsequently, thyroidectomy. FDG PET results were compared with the histopathologic diagnosis of the nodule, lymphocytic infiltrate of thyroid parenchyma, CAT diagnosis and immunohistochemical results of tissue microarray of the tissue from the thyroid nodule and the normal thyroid parenchyma. RESULTS: 1) All the 21 patients with thyroid cancer (11 with indeterminate cytological result) had focal thyroid FDG uptake. 2) Focal FDG uptake was associated with malignancy (p<0.001). 3) From 31 patients with benign nodules whose cytological result was indeterminate, 12 did not display focal FDG uptake (specificity of 39%). 4) Diffuse FDG uptake in thyroid bed was associated with CAT in the histopathologic exam (p=0.019). However, 5 patients without lymphocytic infiltrate had diffuse FDG uptake. 5) Immunoexpression of GLUTs 1, 3 and 12 and hexokinases 2 and 3 by epithelial cells of thyroid nodules was not positively associated with FDG uptake and malignancy. 6) There was no association between diffuse FDG uptake in thyroid bed and immunoexpression of these markers in the normal thyroid tissue. CONCLUSIONS: 1) FDG PET has high sensitivity to the diagnosis of malignancy in thyroid bed, with a specificity of 39% for thyroid nodules with indeterminate cytological result. 2) Diffuse FDG uptake in the thyroid bed is associated with CAT, but can be found in patients without lymphocytic infiltrate. 3) Immunohystochemistry against GLUTs 1, 3 and 12 and hexokinases 2 and 3 does not add in the differentiation of malignant and benign thyroid nodules and is not associated with FDG uptake by these nodules

INTRODUÇÃO: Cerca de 80% dos nódulos de tireóide com citologia indeterminada são benignos. É possível que a tomografia por emissão de pósitrons (PET) com 2-[18F]- fluoro-2-desoxi-D-glicose (FDG) ajude a identificar quais dessas lesões são malignas. A captação de FDG depende da expressão de GLUTs (transportadores de glicose transmembrana) e hexoquinases. Captação difusa de FDG no leito tireoidiano tem ainda sido associada à tireoidite autoimune crônica (TAC), embora haja evidências de que pacientes com parênquima tireoidiano aparentemente sadio possam ter essa alteração. OBJETIVOS: (1) Determinar a sensibilidade e especificidade da PET-FDG no diagnóstico pré-operatório de malignidade dos nódulos tireoidianos, especialmente daqueles com resultados citológicos indeterminados, e avaliar esse desempenho no subgrupo de pacientes com TAC. (2) Determinar a correlação entre o achado de captação difusa tireoidiana da FDG à PET com o diagnóstico histopatológico de TAC e compará-la às concentrações plasmáticas dos anticorpos antitireoidianos. (3) Determinar a correlação entre a expressão dos marcadores imuno-histoquímicos GLUT 1, GLUT 3, GLUT 12, hexoquinase 2 e hexoquinase 3 com o diagnóstico histopatológico dos nódulos e com a captação de FDG apresentada pelos mesmos. MÉTODOS: 56 pacientes com nódulo de tireóide (42 com citologia indeterminada, 10 compatíveis com carcinoma papilífero e 4 com citologia benigna) realizaram PET-FDG e foram submetidos à tireoidectomia. Os resultados da PET-FDG foram comparados com o diagnóstico histopatológico do nódulo, com o infiltrado linfocitário no parênquima tireoidiano, com o diagnóstico de TAC e com os resultados do estudo imuno-histoquímico de micromatriz tecidual de tecido correspondente ao nódulo tireoidiano puncionado e ao tecido tireoidiano não nodular. RESULTADOS: 1) Todos os 21 pacientes com câncer de tireóide (11 com citologia indeterminada) apresentaram captação focal de FDG na tireóide. 2) Captação focal de FDG correlacionou-se com maior risco de malignidade (p<0,001). 3) Dos 31 pacientes com nódulos benignos com citologia indeterminada, 12 não tinham captação focal de FDG (especificidade de 39%). 4) Captação difusa no leito tireoidiano à PET-FDG foi associada à presença de TAC no exame histopatológico (p=0,019). Porém, 5 pacientes, sem sinais de infiltrado linfocitário, apresentaram captação difusa à PET-FDG. 5) Imunoexpressão dos anticorpos contra GLUTs 1, 3 e 12 e hexoquinases 2 e 3 nas células epiteliais dos nódulos não esteve positivamente associada com captação de FDG e com malignidade. 6) Não houve associação entre captação difusa de FDG no leito tireoidiano e imunoexpressão desses marcadores no parênquima tireoidiano não nodular. CONCLUSÕES: 1) A PET-FDG tem alta sensibilidade para diagnóstico de lesões malignas de tireóide, com especificidade de 39% para nódulos com citologia indeterminada. 2) Captação difusa de FDG no leito tireoidiano está associada à presença de TAC, mas pode ocorrer em pacientes sem infiltrado linfocitário. 3) A imuno-histoquímica para os anticorpos contra GLUTs 1, 3 e 12 e hexoquinases 2 e 3 não contribui para a diferenciação de nódulos malignos dos benignos e não se associa com a captação de FDG pelos nódulos / INTRODUCTION: Around 80% of thyroid nodules with indeterminate cytological result are benign. Positron emission tomography (PET) with 2-[18F]-fluoro-2-deoxy- D-glucose (FDG) might help to identify malignant thyroid lesions. FDG uptake depends on GLUTs expression (transmembranous glucose transporters) and on hexokinases. Although diffuse FDG thyroid uptake has been associated with chronic autoimmune thyroiditis (CAT), there is some evidence that patients with apparently normal thyroid parenchyma can display this pattern of FDG uptake. OBJECTIVES: (1) To assess the sensitivity and specificity of FDG PET in identifying thyroid malignancy in the preoperative evaluation of thyroid nodules and evaluate these results in the subgroup of patients with indeterminate cytological results and in the subgroup with CAT. (2) To compare the finding of diffuse FDG thyroid uptake with the histopathologic diagnosis of CAT and with the serum levels of antithyroid antibodies. (3) To evaluate the immunoexpression by thyroid nodules of GLUT 1, GLUT 3, GLUT 12, hexokinase 2 and hexokinase 3 and to compare it with the histopathologic diagnosis of these nodules and with FDG uptake. METHODS: 56 patients with thyroid nodules (42 with indeterminate cytological result, 10 with papillary carcinoma and 4 with benign cytological result) underwent FDG PET and, subsequently, thyroidectomy. FDG PET results were compared with the histopathologic diagnosis of the nodule, lymphocytic infiltrate of thyroid parenchyma, CAT diagnosis and immunohistochemical results of tissue microarray of the tissue from the thyroid nodule and the normal thyroid parenchyma. RESULTS: 1) All the 21 patients with thyroid cancer (11 with indeterminate cytological result) had focal thyroid FDG uptake. 2) Focal FDG uptake was associated with malignancy (p<0.001). 3) From 31 patients with benign nodules whose cytological result was indeterminate, 12 did not display focal FDG uptake (specificity of 39%). 4) Diffuse FDG uptake in thyroid bed was associated with CAT in the histopathologic exam (p=0.019). However, 5 patients without lymphocytic infiltrate had diffuse FDG uptake. 5) Immunoexpression of GLUTs 1, 3 and 12 and hexokinases 2 and 3 by epithelial cells of thyroid nodules was not positively associated with FDG uptake and malignancy. 6) There was no association between diffuse FDG uptake in thyroid bed and immunoexpression of these markers in the normal thyroid tissue. CONCLUSIONS: 1) FDG PET has high sensitivity to the diagnosis of malignancy in thyroid bed, with a specificity of 39% for thyroid nodules with indeterminate cytological result. 2) Diffuse FDG uptake in the thyroid bed is associated with CAT, but can be found in patients without lymphocytic infiltrate. 3) Immunohystochemistry against GLUTs 1, 3 and 12 and hexokinases 2 and 3 does not add in the differentiation of malignant and benign thyroid nodules and is not associated with FDG uptake by these nodules