A 10 year old child develops a testicular mass and undergoes orchiectomy. On cut section, the mass shows a variety of appearances and colors. Histologically, many different tissues are seen, including cailage, thyroid, and neural tissue. A small focus of clear-cut squamous cell carcinoma is seen. Which of the following is the most appropriate classification for this tumor?

This is teratoma with malignant transformation. The possibility of malignant transformation is why even obvious mature teratomas with very well differentiated tissues should be completely excised. Malignant transformation is more common in teratomas in adults than in children or babies. Dermoid cyst is a cystic form of mature teratoma, usually found in the ovaries. Embryonal carcinoma is a type of adenocarcinoma rather than squamous cell carcinoma. Immature teratoma, while clinically malignant, shows embryonal tissues and often displays no clear-cut cytological evidence of malignancy. Ref: Hackam D.J., Grikscheit T.C., Wang K.S., Newman K.D., Ford H.R. (2010). Chapter 39. Pediatric Surgery. In F.C. Brunicardi, D.K. Andersen, T.R. Billiar, D.L. Dunn, J.G. Hunter, J.B. Matthews, R.E. Pollock (Eds), Schwaz's Principles of Surgery, 9e.