IMMUNOHISTOCHEMICAL DEMONSTRATION OF CHROMOGRANIN-A, CHROMOGRANIN-B, AND SECRETONEURIN IN MERKEL CELL-CARCINOMA OF THE SKIN

Using immunohistochemistry the distribution of chromogranins A and B a nd secretoneurin (a biologically active neuropeptide endoproteolytical ly processed from secretogranin II) was investigated in routinely proc essed tissues from 18 Merkel cell carcinomas. The immunolocalization o f these proteins was compared with cytokeratin 20 and epithelial membr ane antigen (EMA) immunostaining. Chromogranin B was present in all ca ses, chromogranin A in 12/18, secretoneurin in 4/18, cytokeratin 20 in 17/18, and EMA in 14/18 cases. Chromogranin A immunoreactivity was st atistically significantly correlated with EMA positivity (p < 0.001) a s well as secretoneurin negativity (p < 0.01), Chromogranin B may thus be proposed as a useful marker for Merkel cell carcinomas. Immunoreac tivity of chromogranins A and B and secretoneurin was mainly found in the characteristic dot-like juxtanuclear pattern. Our observation that chromogranin A is associated with EMA but not with secretoneurin expr ession suggests two different types of Merkel cell carcinoma.