A Case Report of a Spontaneous Gastrointestinal Stromal Tumor (GIST) Occurring in a F344 Rat

• Published in: Toxicologic pathology 2006-01, Vol.34 (2), p.164-167
• Main Authors: Fujimoto, Hitoshi, Shibutani, Makoto, Kuroiwa, Keiko, Inoue, Kaoru, Woo, Gye-Hyeong, U, Mami, Hirose, Masao
• Format: Article
• Language: English
• Subjects: Actins - analysis; Animals; Antigens, CD34 - analysis; Gastrointestinal Neoplasms - chemistry; Gastrointestinal Neoplasms - diagnosis; Gastrointestinal Neoplasms - pathology; Gastrointestinal Neoplasms - veterinary; Gastrointestinal Stromal Tumors - chemistry; Gastrointestinal Stromal Tumors - diagnosis; Gastrointestinal Stromal Tumors - pathology; Gastrointestinal Stromal Tumors - veterinary; Immunohistochemistry; Male; Neoplasm Metastasis; Proto-Oncogene Proteins c-kit - analysis; Rats; Rats, Inbred F344; Rodent Diseases - diagnosis; Rodent Diseases - metabolism; Rodent Diseases - pathology; S100 Proteins - analysis; Vimentin - analysis
• ISSN: 0192-6233; 1533-1601
• DOI: 10.1080/01926230600588588

We report a case of gastrointestinal stromal tumor (GIST) that developed in a male F344 rat at week 101 of an experiment in a carcinogenicity study. Macroscopically, the primary tumor, which measured 1 cm in diameter, involved the submucosal tissue of the forestomach at the lesser curvature extending to the glandular stomach and esophagus. Histopathologically, the tumor was composed of neoplastic cells with small- to medium-sized spindle-shaped single nuclei and fibrillary cytoplasm lacking distinct cell borders. It invaded extensively into the tunica muscularis and subserosa, further extending to the lamina propria mucosa and serosal surface. A few densely proliferating portions showed a tendency to storiform pattern. Metastatic tumor nodules were found in the liver, spleen, and femur bone marrow, with multiple nodules, up to 1 cm in diameter, apparent in the liver. Immunohistochemically, diffuse, but weak cytoplasmic immunoreactivity for KIT was evident, and most neoplastic cells also exhibited strong immunoreactivity for α-smooth muscle actin and vimentin. Sparse nuclear S-100-immunoreactive cells were further observed, but none of neoplastic cells were immunoreactive for CD34, caldesmon, desmin, cytokeratin, or synaptophysin. Collectively, these features meet the criteria for a GIST, with limited potential for differentiation to smooth muscle and neural cells.