Blood muramidase activity in colorectal cancer.

The serum muramidase levels were measured in 128 patients with primary or metastatic colorectal cancer, 166 tumour-free patients after resection of a colorectal cancer, and 172 controls. Muramidase levels over 10 mug/ml were detected in 30%-39% of the tumour-bearing patients, in 8.2% of the tumour free, and in only 1.7% of the controls (normal level 6.68 +/- 1.42 mug/ml). Long-term follow up indicated that raised levels may occur as a transient phenomenon in recurrent or metastatic disease. The likely relation of abnormal serum muramidase activity and stimulation of the reticuloendothelial system is discussed.