Tumour pH in human mammary carcinoma

Human tumour pH was investigated using the new Philips C902S tissue pH electrode. In 22 mammary carcinomas a pH of 7.29 +/- 0.050 (S.E.M.) was observed, whereas in the human subcutis this value was 7.63 +/- 0.034. Tumour pH in some experimental rat tumours was slightly lower than in humans, 7.15 +/- 0.029 in rhabdomyosarcoma BA1112 and 7.07 +/- 0.024 in a small group of other miscellaneous rat tumours. Rat skeletal muscle was found to have a pH of 7.59 +/- 0.070. It is concluded that a small but highly significant (P less than 0.0001) pH difference exists between human mammary carcinoma and human subcutis. This difference is smaller than expected on the basis of animal studies.