Background: Interstitial fluid pressure (IFP) in rodent malignant tumors is reportedly much higher than in surrounding normal tissue. We hypothesized the same may be true in human invasive breast tumors. Methods: We measured IFP in the operating room in 25 patients undergoing excision breast biopsy under local anesthetic for diagnostic purposes. Results: In patients with invasive ductal carcinomas IFP was 29 +/- 3 (SE) mm Hg, compared with -0.3 +/- 0.1 mm Hg in those with normal breast parenchyma (p < 0.001), 3.0 +/- 0.8 mm Hg in those with benign tumors (p < 0.003), -0.3 +/- 0.2 mm Hg in those with noninvasive carcinomas (p < 0.034), and 0.4 +/- 0.4 mm Hg in those with other benign breast conditions (p < 0.002). There was a direct correlation between IFP and tumor size (R2 = 0.3977; p = 0.021). No correlation was found between IFP and nuclear grade, angiolymphatic invasion, systemic blood pressure, metastasis to lymph nodes, or estrogen and progesterone receptors. Conclusions: IFP measurements may facilitate radiographic or ultrasound localization of small or nonpalpable malignant tumors in those patients undergoing needle aspiration cytology or stereotactic core needle biopsy.
