Cutaneous cylindromas are considered to derive from cells of the sweat gland apparatus. The composition of the thick hyaline eosinophilic basement membrane (BM)-like zone surrounding epithelial aggregates in cylindromas is similar to that of the dermo-epidermal junction. The presence of type IV collagen has been documented, but the distribution of the different constitutive a chains of collagen IV has not been studied so far. Alterations in the expression of these α chains have been described in some other conditions including basal cell carcinomas, testes with spermatogenic dysfunction and colorectal carcinomas. The aim was to study the distribution of the α1 (IV) and α5 (IV) collagen chains in cylindromas and malignant cylindroma, and to compare it with the BM of sweat glands. Seven cylindromas and one malignant cylindroma were studied. They were formalin-fixed and paraffin-embedded before processing for immunohistochemistry. Immunostaining was assessed using the avidin-biotin-peroxidase technique with antibodies directed to the α1 (IV) and α5 (IV) collagen chains. In all cylindromas, a thin continuous and sharply limited immunolabelling for the α1 (IV) collagen chain was abutted to the tumoral cell aggregates. A speckled immunoreactivity was found in the rest of the hyaline sheath. Globular structures encased in the cell aggregates also exhibited a thin peripheral rim positive for the α1 (IV) collagen chain. The immunoreactivity was faint and granular in the center of the globules. With the antibody directed against the α5 (IV) collagen chain, 3 cylindromas did not show any staining, 2 cases presented discrete focal positivity in the mid-part of the BM-like zone, and 2 cases exhibited a positive staining pattern similar to that observed for the α1 (IV) collagen chain, but with a focal and more discrete intensity. The malignant cylindroma showed a linear immunoreactivity for the α1 (IV) collagen chain undistinguishable from the pattern seen in the benign cylindromas. No immunoreactivity was present for the α5 (IV) collagen chain in the malignant neoplasm. As reported for other BM components, the expressions of the α1 (IV) and α5 (IV) collagen chains are altered in the BM-like zone surrounding the epithelial clumps in cylindromas. The molecular alteration is probably related to the ultrastructural particularities of this structure. The distinctive patterns of expression of the α1 (IV) and α5 (IV) collagen chains may be related to the histogenic sudoral origin of cylindromas without any relationship with the benign or malignant nature of the neoplasm.

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