Shadow cell differentiation in testicular teratomas. A report of two cases.

Two cases of adult testicular teratoma with shadow cell differentiation (SCD) similar to that seen commonly in pilomatrixoma are presented. The patients aged 21 and 27 years, and both tumors were limited to the testis. The differentiation of squamous epithelium toward shadow cells is well known in cutaneous pilomatrixoma and related lesions, some odontogenic tumors, craniopharyngeoma, and it was recently observed in several visceral carcinomas. In testicular location, SCD was so far described in benign dermoid cyst but not in teratoma, suggesting that the occurrence of shadow cells could help in differential diagnosis between these lesions. This is, however, not the case and the distinction of teratoma from dermoid cyst must be based on other morphological findings.