The expression of
keratins was investigated immunohistochemically on
formalin-fixed and snap-frozen
primary cutaneous amyloidosis tissue with a panel of monospecific and polyspecific antikeratin
antibodies, with recognized
keratins K1, K5, K6, K7, K8, K10, K14, K16, K17,
K18 and K19.
Amyloid deposits in frozen sections of seven cases of macular
amyloidosis and lichen amyloidosus always reacted with
antibodies LP34 (labelling K5, K6 and
K18), MNF 116 (labelling K5, K6, K8, K10, K17 and
K18), and RCK 102 (labelling K5 and K8); frozen sections in one case each of the seven cases also reacted with
antibodies LL001 (labelling K14), LP1K (labelling K7 and K17), and LP2K (labelling K19). In
formalin-fixed sections of 13 cases of macular
amyloidosis and lichen amyloidosus,
amyloid deposits were labelled with LP34 in three sections, MNF 116 in four sections, LL020 (labelling
keratins K5 and K6) in one section, and LP2K in two sections. In nodular
primary cutaneous amyloidosis,
amyloid deposits were not labelled with any antikeratin
antibodies. These data confirm that
amyloid in macular
amyloidosis and lichen amyloidosus contains
keratin epitopes, and suggests derivation of the fibrillar component from
keratin intermediate filaments. Several different
keratins appear to undergo conversion to
amyloid. LP34, MNF 116 and RCK 102
antibodies, which have in common the labelling of
keratin K5, may be useful in the diagnosis of macular and papular
amyloidosis with frozen tissue sections.