Ability of a benign tumor to decrease spontaneous food intake and body weight in rats

Malignant tumors induce anorexia and decrease spontaneous food intake and weight loss. Whether these effects are in part due to the tumor's physical size was investigated by inducing a benign cystic tumor mass with carrageenan in rats and then studying them for 21 days. Forty-two control rats were given subcutaneous injection of 3 ml of normal saline. Fifty-six study rats were given 3 ml of a 1.5% carrageenan solution subcutaneously, both in the right flank. Daily spontaneous food intake, body weight, and tumor weight were measured. Eight study and six control rats were randomly sacrificed on days 1, 3, 5, 7, 10, 14, and 21. Blood was obtained by cardiac puncture for albumin determination, and the tumor, carcass, liver, and spleen were removed and weighed. Tumor and tissue samples were histologically examined. All rats injected with carrageenan developed a benign cystic tumor mass. Early cystic wall consisted mainly of foamy macrophages with a light lymphoplasmacytic chronic inflammatory infiltrate and moderate vascularization. At day 21, cystic wall was more compact. The vasculature had collapsed and there were more pronounced fibroblastic response and collagen bundles. Average tumor weight by day 21 was 41 g. Average spontaneous food intake was depressed by about 15% from day 8 on in study rats as compared to controls. A significant decrease in carcass weight of 15.2% was observed in study as compared to control rats at day 21. Serum albumin was significantly decreased in study rats after day 5. Liver weight was significantly lower and spleen weight higher in study rats as compared to controls. These data suggest that some characteristics associated with cancer anorexia can be found in the absence of malignancy.