Analytical and clinical performance of progesterone receptor antibodies in breast cancer.

OBJECTIVE: Comparison of analytical and immunohistochemical performance of progesterone receptor (PR) antibodies with correlation to recurrence of invasive breast cancer treated with endocrine therapy. METHODS: The binding-affinity kinetics of PR clones 1E2, 1A6, 16 and 636 were compared using synthetic peptides derived from identified epitopes on a Biacore T200. A cohort of 351 cases (Hormone Receptor (HR)+/HER2-) were stained for PR expression with immunohistochemistry (IHC) and scored according to ASCO/CAP criteria. RESULTS: The stability of the antigen/antibody complex was greater for the 1E2 clone compared to 1A6, 16 and 636 clones. PR IHC on archival tissue resulted in 94.3% (299/317) concordance with clones. CONCLUSION: Clones evaluated in this study had a high level of concordance with IHC despite PR (1E2) demonstrating higher analytical binding properties than other clones. In a minority of cases (1.3% for 1E2 and 2.5% for 636) IHC results could convert estrogen receptor (ER)-/PR- to ER-/PR+ tumors, making these patients potentially eligible for endocrine therapy.

A unique collision tumor in breast: invasive ductal carcinoma and mucosa-associated lymphoid tissue lymphoma.

We report an extraordinary case of a collision tumor consisting of invasive ductal carcinoma with adjacent malignant lymphoma presenting as a single mass in the breast. A 79-year-old woman presented with a breast mass. A core biopsy performed at an outside hospital was interpreted as medullary carcinoma. On review of the breast core biopsy, a diagnosis of a synchronous malignant lymphoma and invasive ductal carcinoma was rendered. The patient underwent lumpectomy and axillary dissection. The excised specimen revealed a 2.1-cm, moderately differentiated invasive ductal carcinoma, partially surrounded by malignant lymphoma with areas where both tumors were intermixed. All 27 axillary lymph nodes were extensively involved by lymphoma, and 1 lymph node demonstrated metastatic carcinoma. The morphology and results of immunohistochemistry, flow cytometry, and cytogenetic analysis were consistent with extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue.