Immunohistology, light microscopy, and ultrastructural morphology of transplantable rat medullary thyroid carcinomas
Mcmillan, P.J.; Thaete, L.G.; Hooker, W.M.; Roos, B.A.
Cancer Research 40(5): 1419-1426
1980
ISSN/ISBN: 0008-5472 PMID: 7370980 Document Number: 164245
Three stable MTC production were used for immunohistological, light microscopic and ultrastructural analyses. The fastest growing MTC series (designated 1-1-2) has the lowest CT content. The 2 other MTC series, 1-2-4 and 2-2-10, have somewhat slower growth and 10- to 20-fold higher CT content. Descriptive light microscopic analyses of the tumors distinguished the 1-1-2 series by the presence of active necrosis and scar tissue and by generalized low-intensity immunoperoxidase staining (CT antibodies). Descriptive ultrastructural analyses revealed high concentrations of secretory granules in each of the 3 MTC series. The highest CT-producers (MTC Series 2-2-10) had, in addition to mature secretory granules, a number of less mature, more electron-dense, prosecretory-type granules near the Golgi apparatus. Secretory granules in the 2-2-10 series tumor cells were distributed more peripherally than in the 1-2-4 series. Compared to the 2-2-10 series, the 1-2-4 series exhibited a similar number of coated and prosecretory-type vesicles in the Golgi region. The uniform staining and distribution of mature secretory granules and dilated rough endoplasmic reticulum with few attached ribosomes characterized the 1-2-4 series. The low-CT, fast-growing 1-1-2 tumors exhibited decreased mitochondria, increased lysosomes, increased microfilaments and had features of cells actively elaborating secretory products such as peripheral secretory granules with varying density and prominent dilated Golgi profiles. The prosecretory-type granules occupied a similar volume in this series as in 1-2-4 and 2-2-10. The type of secretory products and their rate of synthesis may differ among the MTC tumors, making these tumors an excellent model system for studying tumor growth and function.