title: Unusual cytoplasmic inclusion bodies in medullary carcinoma of the thyroid gland.
abstract: Medullary carcinoma of the thyroid from a 43-year-old patient showed 4 types of unusual cytoplasmic inclusion bodies ultrastructurally. Type 1 inclusion is composed of rod and doughnut-shaped bodies aggregated in the cytoplasma and not enclosed by a limiting membrane. Typical neurosecretory granules are intermingled with the rod and doughnut-shaped bodies. The doughnut-shaped bodies often have an electron dense core which is similar to the neurosecretory granules. The rod-shaped bodies are bounded by trilaminar unit membrane and have a slightly electron dense matrix. A centriole is often found associated with this type of inclusion. Type 2 inclusion is composed of small secretory granules and clear vesicles. These inclusions can be found either with or without surrounding membrane. Type 3 inclusion is a large osmiophilic body, or secondary lysosome, in which some degenerated organelles are discernible. Type 4 inclusion is a fragmented nucleus with condensation and margination of the chromatin, so-called karyorrhexis. Routine hematoxylin and eosin sections did not show each type of inclusion but semithin sections stained with Paragon suggested 4 different types of inclusions. Type 3 and 4 inclusions represent forms of degeneration and cell death in the tumor cells and probably represent a remote effect of radiation. Type 1 inclusion is not commonly associated with cell death and may represent a unique organellar aberration in these tumor cells. Type 2 inclusion is simply an aggregation of secretory granules and clear vesicles.
mesh_terms: D000328:Adult; D002277:Carcinoma / Q000648:ultrastructure*; D002467:Cell Nucleus / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure*; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D006801:Humans; D002479:Inclusion Bodies / Q000648:ultrastructure*; D008247:Lysosomes / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D013194:Staining and Labeling; D013964:Thyroid Neoplasms / Q000648:ultrastructure*