Transthyretin (Prealbumin) Immunoreactivity in Renal Cell Carcinoma and Other Neoplasms

Transthyretin (prealbumin) previously was identified immunohistochemically in a majority of primary and metastatic renal cell carcinomas, whereas its presence was not detected in other adenocarcinomas. These findings suggested that transthyretin may be useful in differentiating renal cell carcinoma from other morphologically similar neoplasms. To further explore the use of transthyretin as immunohistochemical tumor marker, 24 primary and metastatic renal cell carcinomas of varying architectural patterns, cytoplasmic types, and nuclear grades, as well as tumors of other types that may resemble renal cell carcinoma, were examined with an antitransthyretin antibody using an avidin-biotin-peroxidase complex technique. A variety of normal tissues also was examined to define further the normal spectrum of transthyretin immunoreactivity. Transthyretin was detected in the neoplastic cells of 9 of 13 (69.2%) primary and 10 of 15 (66.7%) metastatic renal cell carcinomas. Transthyretin immunoreactivity correlated with the tumor architectural pattern but not with the type of cytoplasm or nuclear grade. In particular, tumors with an alveolar growth pattern showed consistent staining, whereas tumors with papillary or sarcomatoid growth patterns were more likely to lack transthyretin. In addition, one collecting duct carcinoma lacked prealbumin immunoreactivity. Diffuse transthyretin immunoreactivity was also detected in three of four (75%) hepatocellular carcinomas, and focal staining was present in seven of eight (87.5%) adrenocortical neoplasms, two of two spinal cord hemangioblastomas, one of two papillary carcinomas of the thyroid, one large-cell carcinoma of the lung, and one of four neuroendocrine tumors of the duodenum and pancreas. Other neoplasms studied were negative. Among normal tissues, transthyretin was found in proximal renal tubules, hepatocytes, and pancreatic islets of Langerhans but not in adrenal cortex or medulla, thyroid gland, exocrine pancreas, lung, skin, breast, duodenum, and brain. In summary, these results indicate that immunoreactive transthyretin is widely distributed in normal and neoplastic tissues. Thus, the immunohistochemical detection of transthyretin is of limited use in differentiating renal cell carcinoma from other morphologically similar neoplasms. A recent study by Jacobssen et al. (Histopathology 26:559-564, 1995) suggests that transthyretin immunoreactivity in renal cell carcinomas is due to reabsorption from serum and is not the result of synthesis by renal tubules.