We recently described a patient with chronic lymphocytic leukemia who presented with a breast carcinoma that stained positive for CD5 using a commercially available antibody (CD5-4C7, Novocastra, Newcastle upon Tyne, UK).
To study the distribution of CD5 immunoreactivity in tissue sections of a variety of benign and malignant breast lesions using the antibody CD5-4C7 and to compare the results with those obtained with 2 other commercially available CD5 antibodies (CD5/54/F6, Dako, Ely, Cambridgeshire, UK, and CD5/54/B4, Novocastra).
Paraffin sections of 102 breast biopsy specimens with various diagnoses were examined using the avidin-biotin immunoperoxidase complex technique.
The histopathology department of a tertiary referral teaching hospital.
The staining results obtained with CD5-4C7 were different from those obtained with the other 2 antibodies. With 4C7, the normal and benign biopsy specimens showed varying numbers of positive epithelial cells and lymphocytes. Heterogeneous positive staining was also present in 47 (78%) of 60 invasive female breast carcinomas and in all 3 male breast carcinomas examined. A statistically significant correlation was found between CD5 positivity and tumor grade, with grade 3 tumors being less likely to be CD5 positive than grades 1 and 2 (P =.0035). No correlation was found between CD5 positivity and patient's age, tumor histologic type, axillary lymph node status, or progesterone receptors. On the other hand, the CD5/54/F6 and CD5/54/B4 antibodies only stained lymphocytes and occasional normal breast ducts, mostly those showing apocrine metaplasia. All other normal benign and malignant epithelial cells were negative.
Positive staining for CD5 using the antibody 4C7 is seen in normal and benign breast tissue and 78% of invasive breast carcinomas. The positivity is more common in low-grade tumors. No significant staining was seen with the 2 other CD5 clones used in this study. The significance of the positive staining obtained with CD5-4C7 is not obvious, but this clone may be more sensitive than the others, or it may be recognizing an epitope shared by another antigen.