Apolipoprotein D (Apo D) is a protein component of the human plasma lipid transport system which is present in benign and malignant human breast tissues. This study analysed the expression of Apo D in men with gynaecomastia or breast cancer, and evaluated its use as a prognostic marker in breast cancer. Immunohistochemical expression of Apo D was examined in specimens from 15 men with gynaecomastia, two with in situ breast carcinoma and 68 with invasive male breast cancer. Median follow-up in patients with breast cancer was 44 months. All gynaecomastia specimens, both in situ carcinomas and 57 invasive carcinomas (84 per cent) stained positively for Apo D. Apo D values were significantly correlated with axillary node involvement and histological grade of the tumours. In men with breast cancer univariate analysis showed a statistical association between node status and Apo D content with relapse-free survival (P < 0.001) and overall survival (P < 0.05). Cox multivariate analysis showed that Apo D was a significant indicator of relapse-free survival (P = 0. 0089), but node status was the strongest factor able to predict both relapse-free (P = 0.0336) and overall (P = 0.0346) survival. Apo D was expressed in gynaecomastia and a high percentage of male breast carcinomas. There was a positive association of Apo D content in male breast tumours with favourable outcome. Apo D expression was a significant independent indicator of relapse-free survival in male breast cancer.
