Intratumour amyloidosis in Malaysians: an immunohistochemical study.

Congo red screening of tumour material examined at the Department of Pathology, University of Malaya revealed intratumour deposits of amyloid in 12% of nasopharyngeal carcinomas, 66% of basal cell carcinomas, 100% of medullary carcinomas of the thyroid, 56% of islet cell tumours of the pancreas, 1 out of 16 carcinoids and 1 out of 100 thyroid adenomas. All the deposits were permanganate resistant and did not contain AA protein, indicating that what was encountered was not secondary amyloid. The deposits showed variable staining for immunoglobulin light chains and amyloid P component with a standard peroxidase antiperoxidase method. The possibility that intratumour amyloid has a neoplastic origin is discussed.