Primary cutaneous amyloidosis: A clinicopathological, histochemical, and immunohistochemical study

Abstract

Background: Primary cutaneous amyloidosis (PCA) comprises several forms of localized cutaneous amyloidosis characterized by amyloid deposits occurring at or near dermal–epidermal junctions. Immunohistochemical studies have shown the expression of cytokeratin (CK) suggesting that it has an epidermal origin. Objectives: To study the clinicopathological features of PCA and expression of CK5/6 and correlate it with Congo red stain. Materials and Methods: A total of 30 histologically proven cases of PCA were studied. Congo red staining and immunohistochemical expression of CK5/6 were analyzed. Statistical Analysis: The qualitative data has been expressed as proportions and the quantitative data has been expressed as mean ± SD. All data was analyzed using the Statistical Package for Social Sciences (SPSS) software version 22. Results: Deposits of amyloid in papillary dermis were seen in all 30 cases. Mild focal basal cell vacuolar degeneration and apoptotic bodies in epidermis were seen in six cases. The presence of pigment cells in dermis were seen in 26 cases. CK5/6 showed weak/mild immunopositivity in nine cases, moderate in 20 cases, and strong in one case. Conclusion: The presence of dermal melanophages interspersed within eosinophilic deposits gives a clue to the diagnosis. Congo red stain highlights the deposits and visualization under polarized light gives apple green birefringence which is diagnostic of amyloid. Staining of amyloid deposits by CK5/6 proves that the amyloid is of keratinocyte origin. There was 100% sensitivity with Congo red and CK5/6. Thus, CK5/6 can be used as an adjunct tool to Congo red stain in the diagnosis of primary cutaneous amyloidosis.

Keywords

• amyloidosis
• congo red
• immunohistochemistry