Yolk sac tumors and alpha-fetoprotein in first year of life.

Serum alpha-fetoprotein (AFP) levels are normally elevated in the first eight months of life. This is important information when using AFP as a tumor marker for patients in this age group. We report a case of a one-month-old boy with a yolk sac tumor of the testis. After radical orchiectomy and a negative workup for metastatic disease, his AFP level dropped, but remained mildly elevated over the normal range for six months. Using a half-life of five days it was predicted that it would fall into this range in eighty days. Although the elevated levels suggested residual tumor, they did continue to decline each month which led us to pursue some other explanation for this pattern. A literature search revealed the AFP levels are normally elevated in this age group. In retrospect, our patient's AFP was within this range less than sixty days after surgery. Dissemination of knowledge that the normal AFP ranges in young infants are higher than those in older patients will improve the clinical usefulness of AFP as a tumor marker in this age group.