Expression of amine oxidase-related proteins in breast phyllodes tumor.

Bacground: Breast phyllodes tumors (BPTs) are difficult to differentiate from other tumor types. In-depth research is needed due to the insufficient description of the amine oxidase protein family, particularly in BPTs.

Objective: This study investigated the expression and clinical implications of amine oxidase-related proteins in BPTs.

Methods: Tissue microarrays were constructed (n=181), and amine oxidase-related proteins of monoamine oxidase (MAO) A, MAOB, lysyl oxidase (LOX), and primary-amine oxidase 3 (AOC3) were assessed using immunohistochemical staining. Staining patterns of these proteins were compared and analyzed with clinicopathologic parameters.

Results: In all, 149, 27, and 5 cases were classified as benign, borderline, and malignant, respectively. A higher grade of BPT was associated with increased MAOB (P<0.001), LOX (P=0.035), and AOC3 (P<0.001) expression. BPT cases with tumor recurrence and distant metastasis had higher proportions of MAOB positivity in stromal components (P=0.002 and 0.018, respectively). During follow-up, there was a significant association between MAOB positivity in the stromal component and shorter disease-free survival (DFS) (P=0.001) as well as overall survival (P=0.003). Moreover, MAOB positivity emerged as an independent factor for shorter DFS (hazard ratio: 4.253, 95% confidence interval: 1.034-17.49, P=0.045).

Conclusions: Higher MAOB, LOX, and AOC3 expression were observed in higher-grade BPTs, and MAOB expression was identified as a significant prognostic factor.