Immunohistochemical characterisation of a case of insular thyroid carcinoma

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Abstract
Summary A case of insular thyroid carcinoma arising in the right lobe of a 54-year-old male is reported. The tumour exhibited an invasive growth pattern with regional lymph node metastasis. Microscopically, the tumour was characterised by well-defined solid nests like insulae, including mature follicles containing colloid and immature follicles without colloid. Immunohistochemically, tumour cells in follicular areas predominantly exhibited immunopositivity to anti-thyroglobulin antibody. On the other hand, diffuse immunoreactions with anti-neuron-specific enolase (NSE), S-100 protein and Leu-7 were detected mainly in the tumour cells of solid areas. In addition, clear cytoplasmic immunoreactivity with anti-myelin basic protein (MBP) antibody was exhibited in a number of tumour cells. Ultra-structurally, many tumour cells possessed dense vacuoles, apparently containing colloid material, but intracytoplasmic neurosecretory granules were absent. The histopathological and ultrastructural characteristics of the tumour as well as its anti-thyroglobulin antibody immunoreactivity support the classical hypothesis that this neoplasm is a variant of poorly differentiated thyroid carcinoma. The positive immu-nohistochemical reactions for NSE, S-100, MBP and Leu-7 raise the possibility of aberrant differentiation, for example neural.