Histophotometry of protein thiols and disulphides in tissue samples from the human uterine cervix and the skin reveals a "field effect" as well as an "extended field effect" of malignant tumours.

Fresh frozen and fixed serial sections were stained with 2,2'-dihydroxy-6,6'-dinaphthyldisulfide (DDD) and Fast blue B for reactive protein thiols (PSHr) and total reactive protein sulfur (TRPS). The mean optical densities of PSHr and TRPS determined histophotometrically at a distinct part of a tissue were related to each other (PSHr: TRPS). If this quotient has been determined, e.g. for normal epithelium and the adjacent stroma, both quotients can be related to each other by a double quotient (Q PSHr: TRPS). With the aid of the double quotient highly significant differences could be found between tumours and normal tissue from patients without tumour of the human uterine cervix. Similar differences exist between normal skin from healthy patients and skin tumours. Q PSHr: TRPS revealed similar differences to exist between normal tissue of patients without tumour and apparently normal tissue in the neighbourhood of tumours of the uterine cervix and of skin ("field effect" of tumours). Histophotometric investigations on abdominal skin (and skin of breast) showed highly significant differences between normal skin of patients without tumour and patients with various kinds of tumours of the uterine cervix, ovaries, liver and breast ("extended field effect" of tumours).