A spontaneous testicular teratoma in an ICR mouse.

A spontaneous teratoma was detected in the left testis of a 7-wk-old male ICR (Crj:CD-1) mouse. The tumor was composed of a variety of well-differentiated tissue elements from all 3 germ layers including neuronal tissue and stratified epithelium as ectoderm-derived tissues, bone, cartilage, striated muscle, and adipose tissue as mesodermal tissues, and respiratory columnar epithelium as endoderm-originated tissue. No tumor metastasis was detected. It may be of congenital origin as in strain 129 mice. To the best of our knowledge, this is the first report concerning spontaneous testicular teratoma in a strain ICR mouse.