Facilitation of tumor metastasis by operative stress and participation of cell-mediated immunity. Experimental study

5-week-old syngeneic female SD rats were inoculated subcutaneously at the dorsal flank with 200 mg of a metastasizing rat's mammary tumor, MRMT-1. A significantly higher incidence of lung metastasis was observed in the cases in which tumor excision on day 14 was accompanied by 30 min laparotomy than in the cases of simple tumor excision. PHA lymphoblastogenesis on day 17 was significantly lower in the cases of tumor excision plus laparotomy on day 14 than in the cases of simple tumor excision. Winn's assay using splenocytes revealed a postoperative enhanced suppressor activity in the cases undergoing laparotomy stress. Possible participation of the raised suppressor activity to facilitation of metastasis was discussed.