S_lThe retrospective analysis of 250 breast cancer patients with disseminated disease provided evidence that the increase in CA 125 serum levels in these patients was caused by lung metastases or pleural effusions. Seven patients with lung metastases and pleural involvement had elevated CA 125 levels, while in four patients with lung metastases but without pleural effusions CA 125 levels remained normal. In patients with only bone or liver metastases ResultsOf a group of 250 patients with disseminated breast cancer, only 26 fulfilled the inclusion criteria. Most patients were excluded because multiple metastases were detected or could not be ruled out within 6 months after the detection of the first metastases. The final distribution of isolated metastases in these 26 patients was as follows: bone = nine patients (premenopausal: two patients), liver = six patients (premenopausal: four patients) and lung= 11 patients (premenopausal: five patients).The CA 125 levels at the time of detection of these metastases are shown in Figure 1. As can be seen, 7 of the 11 patients with lung metastases had elevated CA 125 serum levels (three premenopausal and four post-menopausal patients), while only one of nine patients with bone metastases (post-menopausal patient) and one out of six patients with liver metastases had high CA 125 levels (post-menopausal patient). Of the seven patients with lung metastases and elevated CA 125 levels, five had pleural effusions when the metastases were detected. The other two patients developed a pleuritis carcinomatosa with pleural effusions within 4 weeks of the diagnosis of the lung metastasis. The remaining four patients with normal CA 125 levels did not develop pleural effusions. The patient with high CA 125 levels and bone metastasis was shown post mortem (7 months later) to have pleuritis carcinomatosa, which had not been previously detected. The serial CA 125 measurements showed that in some patients the CA 125 concentration increased months before the detection of the metastasis (Figure 2). In the one patient with a liver metastasis and elevation of CA 125, the endocrine and metabolic function of the liver was impaired. In this patient serum aspartate transaminase (AST), serum alanine transaminase (ALT) and serum glutamyl transferase (GGT) were elevated.