Peritoneal sarcomatosis associated with telemetry implants in Sprague Dawley CD rats: a review of eight cases.

Surgical implantation of radiotelemetric transmitters is a current practice to collect a variety of physiological parameters in unrestrained laboratory animals, and in rodents in particular. In this study, the incidence of peritoneal sarcomatosis arising secondary to surgically implanted telemetry devices (< 15% of implanted Sprague Dawley rats) is considered to represent a significant issue for both animal welfare and data validity in affected animals. Macroscopically, the telemetry-associated fibrosarcomas spread along the visceral and parietal peritoneum and mesentery surrounding abdominal organs. The histologic morphology of these sarcomas was typically an undifferentiated sarcoma, although well-differentiated fibrosarcomas and telangiectatic and pleomorphic variants were noted. Using special stains such as Masson's Trichrome demonstrated a collagenous extracellular matrix in 50% of these rats, which is consistent with a fibroblastic origin. Immunohistochemical studies clearly delineated the mesenchymal components of the sarcomas (fibroblasts and smooth muscle cells); one case, however, was diagnosed as an osteosarcoma.