QBEND 10 (ANTI-CD34 ANTIBODY) IN EXTERNAL ROOT SHEATH-CELLS AND FOLLICULAR TUMORS/

The human hematopoietic progenitor cell antigen (CD34) is a cell surfa ce protein expressed by human hematopoietic progenitor cells, vascular endothelium, and many mesenchymal tumors. Sections from six samples o f normal skin and from 41 epithelial tumors of the skin were studied. Immunostaining of epithelial cells from the external root sheath below the attachment of the arrector pili muscle and above the matrix cells was noted in normal samples. Tumors derived from or differentiated to ward cells of the outer sheath, especially trichilemmomas, were immuno stained with QBEND/10 (anti-CD34 antibody), whereas other epithelial t umors studied were negative. CD34 could serve as a marker of outer she ath cell derivation and may well be of value in the distinction betwee n trichilemmomas and other lesions with similar histopathological feat ures.