A case of primary testicular germ cell tumor with rhabdomyosarcoma metastases as an example of applying the FISH method to diagnostic pathology.

We present the interesting case of a 38-year-old man with a primary malignant tumor of the right testis that metachronously metastasized to the urinary bladder and the stomach. Histologically, the testicular tumor was a mixed germ cell tumor composed of teratoma and embryonal carcinoma, but it also contained a sarcoma component of somatic type malignancy. Metastases showed rhabdomyoblastic differentiation histologically identical to the sarcoma component of the testicular tumor that was diagnosed as rhabdomyosarcoma. By applying fluorescence in situ hybridization (FISH) to the cytogenetic examination of cells taken from the periventricular lymph node metastases, we demonstrated a structural chromosomal aberration characteristic of testicular neoplasms, i.e. the presence of isochromosome 12p (i(12p)). Additionally, the diagnosis was supported by immunohistochemistry.