Basal cell carcinoma possibly originates from the outer root sheath and/or the bulge region of the vellus hair follicle.

In the present study, the immunophenotype of basal cell carcinoma was analysed in comparison with human vellus hair follicular keratinocytes. We also established the lectin binding profile of basal cell carcinoma and human vellus hair follicles (VHF), using several lectins with different sugar specificities. Our findings showed an almost identical immunohistochemical profile for basal cell carcinoma and the suprabulbar region of the outer root sheath of VHF, whereas other follicular compartments such as the bulbar, the isthmus or the supraseboglandular regions did not correlate. In particular, homogeneous and constant expression of the basal differentiation markers CK 5 and CK 14 were found in both specimen, with no expression of the simple epithelium type keratin CK 8 and the suprabasal differentiation markers CK 1 and CK 10. CK 19 showed variable expression in basal cell carcinoma, with constant expression in the outer root sheath and the follicular bulge regions, but was always absent in interfollicular epidermal keratinocytes. In addition, the lectin binding profiles of basal cell carcinoma and the outer root sheath in the suprabulbar region of human VHF were comparable, with the presence of binding sites for PNA, Con A and WGA. These findings provide evidence for a histochemical relationship between basal cell carcinoma and the follicular epithelium of VHF which is closer than that with the epidermis, and suggest its possible origin from or possibly its differentiation pattern towards the cells of the outer root sheath and/or the follicular bulge region of the VHF.