The Utility Of Congo Red Stain And Cytokeratin Immunostain In The Detection Of Primary Cutaneous Amyloidosis

摘要

Background: Primary cutaneous amyloidosis includes several forms of localized amyloidosis characterized by superficial amyloid deposits occurring at or near the dermal–epidermal junction. This type of amyloidosis is derived from keratin presents in basal keratinocytes.Aims: To compare the cytokeratin immunohistochemoical stain and Congo red stain for the detection of primary cutaneous amyloidosis.Methods: We examined 19 cases of cutaneous amyloidosis stained with hematoxylin–eosin, Congo red and the cytokeratin immunohistochemical stain.Results: Most of the cases (16/19) examined were negative for Congo red stain, but all of the cases were positive for the cytokeratin immunohistochemical stain.Conclusion: Congo red is not useful for the detection of cutaneous amyloidosis. The cytokeratin immunohistochemical stain is superior to Congo red and can detect very small amount of amyloid. Introduction Primary cutaneous amyloidosis can be easily diagnosed by a dermatopathologist on hematoxylin - eosin (H&E) stained slides. General pathologists can detect amyloid deposits as extracellular eosinophilic material, and Congo red staining is usually performed for confirmation. Primary cutaneous amyloidosis is derived from epidermal keratinocytes and is therefore positive for the cytokeratin immunohistochemical stain. In our experience, cases of primary cutaneous amyloidosis generally stain negative when using Congo red. In this study, we compare the cytokeratin immunohistochemical stain and Congo red stain for the detection of primary cutaneous amyloidosis. Materials and methods We retrieved the slides and blocks of 19 cases of primary cutaneous amyloidosis from our histopathology lab files at King Khalid University hospital. The cases included macular amyloidosis (16) and lichen amyloidosis (3). The clinical features of the cases were described. In all cases, we examined hematoxylin-eosin stained slides and slides stained with Congo red and the cytokeratin 5/6 immunohistochemical stain (CK5/6) (Roche, Germany). Congo red stained slides were also examined under polarized light. A positive control of non cutaneous amyloidosis was used for comparison. Results A total of 19 cases of primary cutaneous amyloidosis were identified. Of these, 16 were from women (84.2%) and 3 were from men (15.8%). The mean age was 39 years (range: 20-61 years). Among cases of macular amyloidosis (16/19), the back was the most common site of involvement (12/16); other sites included the leg (2 /16), forehead (1 /16) and arm (1 /16). The extensor surface of the leg was the site of involvement in the 3 cases of lichen amyloidosis.Histopathologically, all cases showed a homogenous esinophilic deposits within widened dermal papillae (Figure 1). However, the quantity of the deposits varied. In 2 of the cases, the deposits were very minimal and questionable. Congo red staining was positive in the positive control case (Figure 2), but it was negative in (16/19) cases (84.2%) (Figure 3A). Faint positivity was noted in (3/19) cases (15.8%) (Figure 3B). Only one case showed apple green birefringence under polarized light (Figure 3C).