Histology Course A III 29 Department of Pathology, University of Zurich Histology Course

A III 29 medullary thyroid carcinoma (c-cell carcinoma) with amyloid Congored  
  ICD-10: C73; ICD-O: 8345/3
40-year-old female underwent thyreoidectomy because of an isolated 'cold' nodule of the thyroid. She had suffered of diarrhea for months. Serum levels of calcitonin and carcino-embryonic-antigen (CEA) were elevated.
- The thyroid parenchyma is destroyed by a nodular tumor.
- The tumor exhibits an infiltrative and destructive growth pattern, is irregularly delimited and shows vascular invasion.
- The tumor cells are arranged in sheets, nests and trabeculae.
- Tumor cells are round to oval or spindle-shaped with elongated nuclei.
- Nuclei show a punctuate chromatin pattern and little variation in size.
- Mitotic figures are frequent.
- Nests of tumor cells are separated by various amounts of stroma staining intensely with Congo red.

Amyloid in medullary thyroid cancer is composed of procalcitonin and possibly of amylin. The latter is also observed in insulinoma.