Focal lobular spermatogenesis and pubertal acceleration associated with ipsilateral Leydig cell hyperplasia.

Leydig cell tumors of the testis are the underlying cause in about 10% of the cases of precocious puberty in boys. Leydig cell hyperplasia is a less well-characterized cause, with an undocumented frequency. We describe a boy with precocious puberty associated with ipsilateral testicular enlargement and focal Leydig cell hyperplasia with spermatogenesis limited to the local adjacent testicular tissue.