Medullary Thyroid Carcinoma(MTC) was first described by Hazard et al.
and it is known to be C-cell origin and one of the members of APUDomas.
Recently we have studied ultrastructural characteristics of 17 cases of MTC
and this report describesultrastructural features of an unusual case in
which 4 types of cytoplasmic inclusions other than typical secretory
granules and ordinary cytoplasmic organelle were observed. The clinical and
histologic features of this case were typical of the MTC and the patient was
treated with Co radiation 90 days prior to the surgery.
Small pieces of the tumor tissues(lymph node metastasis) obtained from
43 year-old male patient at total thyroidectomy and left modified neck
disection were prepared for transmission electron microscopy by standard
methods.
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.
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