Angiogenesis of human parathyroid tissue.

The etiology of parathyroid disease remains obscure. The terms "adenoma" and "hyperplasia" imply neoplastic and nonneoplastic processes, respectively. Angiogenesis, the ability of transplanted tissue to evoke new blood vessel formation by the host, is a property generally attributed to neoplastic tissue. We tested human parathyroid tissues from six patients with clinical diagnoses of adenoma and four patients with hyperplasia for their ability to evoke angiogenesis in an established in vivo model. Six to 12 small pieces of parathyroid tissue from each patient were placed on the iris of New Zealand white rabbits, three pieces per eye. Macroscopic assessment of angiogenesis was performed on days 2 through 5 after implantation by a noninformed observer. Microscopic assessment of implant viability was made after the animal was killed on day 5. Some implants were lost to infection, necrosis, and failure to attach to the iris. Both adenomatous and hyperplastic human parathyroid tissue demonstrated angiogenesis, and with approximately the same frequency. However, there was considerable variation in response of tissue from the same patient and between patients with the same clinical diagnosis. The ability of human parathyroid tissue to evoke angiogenesis may help explain its relative ease of transplantation.