Orbital malignant schwannoma and embryonal rhabdomyosarcoma in rats caused byleakage of locally injected nickel subsulfide to the orbit

摘要

Nickel subsulfide (Ni3S2) is known to induce intraocular neoplasmswhen injected intravitreally into the eyes of rats. Here, we found two extraocular orbitalneoplasms in two different rat strains, presumably due to the leakage of locally injectedNi3S2 to the extraocular orbital tissues. In the F344/DuCrlCrljrat, an orbital mass arose at 30 weeks after injection, and invaded into the cranium.Histologically, the orbital mass was composed of areas arranged in parallel bundles formedby densely packed elongated or spindle-shaped cells with indistinct cytoplasmic borders,and of areas of hypocellular arrangement consisting of round cells in eosinophilicmyxoid-like substances. Metastases were observed in the right submandibular and cervicallymph nodes. The neoplastic cells were immunopositive for S-100 protein and vimentin.Transmission electron microscopy revealed that the neoplastic cells had cellular processesand pericytoplasmic basal laminae. In the RccHanTM:WIST rat, an orbital massarose at 36 weeks after injection. Histologically, the mass consisted of rhabdoid-likelarge round cells with proliferation of small round-to-polygonal cells, and theseneoplastic cells infiltrated into the extraocular muscles. Immunohistochemically, theneoplastic cells were positive for desmin and vimentin. Transmission electron microscopydetected immature myofibrils with Z-band structures in the cytoplasm of these neoplasticcells. Consequently, the tumors were diagnosed as an orbital malignant schwannoma in anF344/DuCrlCrlj rat and an orbital embryonal rhabdomyosarcoma in a RccHanTM:WISTrat. The results of this case report suggest that leakage of Ni3S2to the orbit caused the induction of orbital malignant schwannoma or rhabdomyosarcoma inrats.