Neuroendocrine differentiation in hyalinizing trabecular tumor of the thyroid.

The presence of neuroendocrine cells is putative in thyroid hyalinizing trabecular tumor (HTT), although this entity requires a differential diagnosis from paraganglioma or medullary carcinoma of the thyroid, due to similarity of the growth pattern of the cells. Here, we present a case of HTT with a mixture of endocrine cells stained positive for somatostatin, chromogranin A and Grimelius' silver impregnation. The histology and results of other immunostainings were consistent with the features typical for HTT. In the world literature to date, only two cases of HTT with endocrine cells, including the current case, have been reported. Nevertheless, the cases may indicate the diversified differentiation of cells in HTT and may, in part, account for the resemblance of HTT to paraganglioma and medullary carcinoma.

Localized amyloidosis at the site of repeated insulin injection in a diabetic patient.

A 60-year-old woman diabetic patient presented with a subcutaneous mass in right lower abdominal quadrant where recombinant human insulin or insulin analogue had been injected for 16 years. Her diabetes has been insulin resistant with insufficient blood glucose control. The mass was extirpated under the suspicion of neoplasm but it was found to consist of diffuse deposition of eosinophilic amorphous materials mixed with inflammatory change. Congo-red staining demonstrated positive red color and yielded green birefringence by polarized microscopy. Pre-digestion with potassium permanganate was incomplete to quench positive Congo-red stains. Immunostains with insulin antibody were positive for this deposition but not so with amylin or AA or AL amyloid. Thus, the mass was considered to be localized amyloidosis composed of iatrogenic A-Ins type amyloid. Thus, the case suggested that her insulin resistance, i.e. refractoriness of insulin treatment, may be ascribed to poor penetration of injected insulin and human insulin itself or its analogue is amyloidogenic to form a local mass.