PRL and neoplasm: The tumor cells were largely distinguished according to hormone-encoded genes: the cells with high expression of only somatotropin (T01, T02), high expression of only prolactin (T03, T04), and high expression of both hormones (T05, T06) were found in PIT1-positive tumors, while the cells with high expression of gonadotropin (T11) and melanocortin (T12) were found in PIT1-negative tumors (Fig. 2e, f).