Immunocytochemical and serological expression of CA 125: a clinicopathological study of 40 malignant ovarian epithelial tumours

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Abstract
Elevated serum levels of the tumour‐associated antigen CA 125 occur in more than 80% of cases of ovarian carcinoma. The antigen can be demonstrated in formalin‐fixed tissue using the monoclonal antibody OC 125, which localizes it to the surface membrane or cytoplasm. This study was performed to determine the relationship between pre‐operative serum levels of CA 125 and the subsequent immunocytochemical findings in the surgical specimen. Paraffin‐wax embedded sections from 40 consecutive borderline and frankly malignant ovarian epithelial tumours were stained with OC 125. The pattern and distribution of immunostaining were investigated in relation to histological appearances. Serous tumours showed a 100% correlation between immunocytochemical findings and elevated serum levels of CA 125. Amongst the other histological types, correlation was less good; mucinous tumours and undifferentiated carcinomas showed a poor correlation. Immunostaining within tumours was heterogeneous and only loosely related to morphological appearances. Our finding suggests that, with the exception of serous tumours, immunolocalization of CA 125 is insufficiently sensitive to provide reliable clinical guidance to the likely value of serum CA 125 monitoring on follow‐up.