TG2 expression in tumor tissue samples from patients with breast cancer. Paraffin-embedded tissues from the primary tumors were retrieved from the Tumor Tissue Bank in the Department of Pathology at The University of Texas M. D. Anderson Cancer Center. The tissue sections were processed for immunostaining as described in Materials and Methods. One hundred samples each from patients with or without lymph node metastasis were studied and independently scored by a pathologist and a laboratory technician for TG2 expression. The figure shows the extent of TG2 expression in the primary tumor cells and the stroma surrounding the tumor from eight representative patients. a and b, tumor samples from representative patients (14% of patients) in which TG2 expression was mainly localized in the stroma; c and d, tumor samples from representative patients (23% of patients) in which TG2 expression was mainly localized in the tumor; e and f, TG2 expression in some patients' tumor samples (13% of patients) was observed both in the tumor and the stroma; g and h, half of all patients (50%) showed almost a complete lack of TG2 in the tumor and the stroma. The TG2-positive cells in g and h were endothelial cells that had high constitutive TG2 expression.