Metastatic invasive lobular carcinoma (ILC) exhibits substantial patient-to-patient differences in key prognostic and predictive markers. This variability raises concerns about the accuracy of single-site biopsies for guiding treatment.
Research examining metastatic ILC through postmortem tissue donation programs revealed significant differences in stromal tumor infiltrating lymphocytes (sTIL), estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and KI67. A total of 306 metastases from 12 patients were analyzed.
Regression modeling showed significantly lower ER and PR expression in metastases compared to primary tumors. KI67 expression was notably higher in metastases. HER2 low metastases were identified in most patients, though the proportion varied widely.
Radiology and pathology reviews indicated moderate concordance in detecting metastatic ILC, with discrepancies between imaging and pathological assessments. This suggests potential implications for disease monitoring.
These findings imply that relying on a single metastatic biopsy may not fully represent the biological landscape of metastatic ILC. The observed heterogeneity in hormone receptor expression, proliferation index, and HER2 status necessitates more comprehensive strategies for detecting and monitoring metastases. Clinicians must consider tumor variability when planning therapeutic strategies for patients with metastatic ILC.