How do cardiac allografts differ from renal allografts? a. Cardiac allografts are matched by HLA tissue typing and renal allografts are not b. Cardiac allografts can tolerate a longer period of cold ischemia than renal allografts c. One-year graft survival for cardiac allografts is substantially lower than that for renal allografts d. Cardiac allografts are matched only by size and ABO blood type e. Cyclosporine is a critical component of the immunosuppressive regimen for cardiac allografts but not renal allografts
The correct answer is D. An isolated thyroid nodule is a frequent finding in asymptomatic adults, and most of such nodules are benign. Fine needle aspiration allows a diagnosis in most cases. The material aspirated with a needle is smeared on a slide and stained. In only 15% of cases is the aspirated material "non-diagnostic." Suspicious cases are followed with repeated fine needle aspiration. Malignant nodules are usually large (>3 cm) and/or fixed to the surrounding parenchyma. Papillary carcinoma is the most common malignant thyroid neoplasm. Ultrasonography may also be of value in distinguishing solid from cystic nodules and is preferred to MRI scan (choice A) or CT scan (choice B) because of its high sensitivity and lower cost. However, CT and MRI are valuable in defining the extent of malignant tumor, once the diagnosis is made. Radioactive iodine scan (choice C) is needed when a solitary thyroid nodule is associated with symptoms of thyrotoxicosis. Radioactive iodine scan helps to distinguish a toxic adenoma from Graves disease, in which high uptake is seen in the whole gland. Excision of a thyroid nodule (choice E) is performed if it proves to be malignant, or in case of a hot (i.e., hyperfunctioning) nodule causing thyrotoxicosis.
