Introduction In breast cancer, attention has focused on the prognostic value of tumor- stroma ratio (TSR), mainly in the triple-negative subtype, which generally has a poor prognosis.

Little prognostic data are available for other carcinoma types.

Objective To determine the prognostic value of TSR in estrogen receptor (ER) positive invasive breast carcinomas.

Methods TSR was measured in hematoxylin and eosin-stained surgical specimens of 70 consecutive EP positive breast carcinomas. Tissue from the most invasive part of the tumor was used. A part of the sample was selected where both tumor and stromal tissue were available. Scoring percentages were given per 10-fold per image field.

Tumors with a low ratio had ≥50% of stroma and a high ratio had <50% of stroma.

The relationship of TSR to routinely used prognostic histopathological parameters (tumor size, grade, mitotic activity index, lymph-node status, vascular invasion, and HER2 status) was analyzed.

Results All tumors were of no special type. The mean age of patients was of 65 years. There was no multifocality. Sixty percent of tumors had a high ratio and 40% a low ratio.

High ratio tumors were significantly correlated with large size (p=0.02), grade 3 (p=0.045), presence of vascular invasion (p=0.0034) and lymph node metastasis (p=0.0012). No significant association was found with the mitotic activity index and HER2 status.

Conclusion High TSR was related to poor histopathological parameters in EP positive breast carcinomas, contrasting data in triple-negative breast cancer, and highlighting the importance of considering ER status when interpreting the prognostic value of TSR.