RESUMEN
Precocious thelarche usually results from a physiological process but can sometimes be the first sign of precocious pseudopuberty. Ovarian granulosa cell tumors are highly unusual in childhood, appearing as precocious puberty in most prepuberal patients. During adolescence these tumors may cause menstrual irregularities, virilization and abdominal pain. Their malignancy is low and surgical treatment is usually curative if the tumors are limited to the ovaries. More advanced stages require chemotherapy, are difficult to cure and produce high mortality. We present the case of a 16-month-old girl with a granulosa cell tumor who presented with progressive precocious thelarche over 1 month that was satisfactorily resolved after resective surgery. This case demonstrates that other causes of puberal development should be investigated when precocious thelarche with fast progression is observed, with special attention paid to tumoral disease in the differential diagnosis.