Amyloid deposits in basal cell carcinoma of the skin. A pathologic study of 199 cases.

Deposits of amyloid were detected in 101 of 199 basal cell carcinomas (51%). The frequency of amyloid deposits in solid, adenoid, and cystic histologic subtypes was slightly higher than overall, whereas in partial sclerosing and morphea-like tumors the frequency was much lower. The amyloid of basal cell carcinoma showed histochemical characteristics that were different from those of locally deposited amyloid in endocrine tumors such as medullary carcinoma thyroid and from those of "secondary" amyloid. No major differences in the histochemical characteristics, however, were observed between amyloid associated with basal cell carcinoma and myeloma-associated or "primary" amyloid. Nevertheless, immunohistochemical staining with rabbit antihuman keratin antibodies by the peroxidase antiperoxidase technique demonstrated positivity only in amyloid deposits associated with basal cell carcinoma and not in those of myeloma-associated amyloid. This evidence supports the concept that amyloid of basal cell carcinoma is produced in the stroma from degenerated epithelial cells through filamentous degeneration or apoptosis.