Immunohistochemical characterisation of a case of insular thyroid carcinoma

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 characteris ed by well-defined solid nests like insulae, including mature follicles con taining colloid and immature follicles without colloid. Immunohistochemical ly, tumour cells in follicular areas predominantly exhibited immunopositivi ty to antithyroglobulin antibody. On the other hand, diffuse immunoreaction s with anti-neuron-specific enolase (NSE), S-100 protein and Leu-7 were det ected mainly in the tumour cells of solid areas. In addition, clear cytopla smic immunoreactivity with anti-myelin basic protein (MBP) antibody was exh ibited in a number of tumour cells. Ultrastructurally, many tumour cells po ssessed dense vacuoles, apparently containing colloid material, but intracy toplasmic neurosecretory granules were absent. The histopathological and ul trastructural characteristics of the tumour as well as its anti-thyroglobul in antibody immunoreactivity support the classical hypothesis that this neo plasm is a variant of poorly differentiated thyroid carcinoma. The positive immunohistochemical reactions for NSE, S-100, MBP and Leu-7 raise the poss ibility of aberrant differentiation, for example neural.