Host origin of lymphoid cells in thymomas developed from subcutaneous thymus grafts in Buffalo rats.

Ten out of 31 male Buffalo rats developed thymomas, 18 months after birth, from the subcutaneous thymuses grafted neonatally either from female or male litter mates. Most of them were of lymphoid cell type and contained numerous lymphoid cells within the network composed of neoplastic epithelial cells, as mediastinal thymomas. Lymphoid cells in the subcutaneous thymomas had normal diploid karyotype and were of host type with the Y chromosomes. These facts may indicate that lymphois cells intermingled in the network of neoplastic epithelial cells are non-neoplastic in nature.