Histochemical and immunohistochemical differential diagnosis of amyloidosis--a brief illustrated essay and personal experience with Romhányi's method.

The histochemical and immunohistochemical differential diagnosis of amyloidosis in surgical pathology in a referral center is presented. Different forms of amyloidosis are considered e.g. systemic generalized amyloidosis: secondary (AA), primary (AL), senile, hemodialysis-associated, hereditary and organ (tissue)-limited (localized) amyloidosis: cerebral, dystrophic (age-related, so-called "senile"), endocrine-related, localized to tumours, focal (concentrated secretion), and isolated plasma cell (solitary plasmacytoma, B-cell) dyscrasia related amyloidosis. The amyloid deposits were identified and characterized histochemically by Congo red staining after performate pre-treatment at 20 degrees C for 1, 3, 5, 10, 15, 20 or 25 sec, and with oxidation induced proteolysis by trypsin digestion at 20 degrees C for 5, 10, or 30 sec, 1, 2, 3, 4, 5, 6 or 10 min and covered with gum-arabic according to Romhányi, and confirmed by streptavidin-biotin-complex/horseradish peroxidase immunohistochemical reactions. The "sensitivity" or "resistance" to pre-treatment of amyloid deposits depends on the type of amyloid, and the length of pre-treatment. Secondary (AA) amyloid is sensitive to KMnO4 oxidation, followed by trypsin digestion (for 1 min), and its green birefringence under polarized light disappears, while primary (AL) (for 1-5 min), senile (for 1-10 min), and most forms of organ (tissue)-limited (localized) amyloid (for 1-10 min) are resistant. Performate pre-treatment is followed by pronounced congophilia. Secondary (AA) is sensitive to performate pre-treatment (for 1 sec), while primary (AL) amyloid (for 1-20 sec), senile (for 1-25 sec), and most forms of organ (tissue)-limited (localized, isolated) amyloid deposits (for 1-25 sec) are resistant, and are constantly positively birefringent. Early identification and differentiation of amyloid deposits is important for the prognosis and for the choice of therapy. The authors conclude that the presented classical histochemical methods are useful as first line screens for the histological identification of amyloidosis.