Detection of Ig heavy and light chain transcripts in classical HD by in situ hybridization using radioactively labeled probes for the according constant region.

(A) IgL kappa; (B) IgL lambda; (C) IgH mu; (D) IgH delta; (E) IgH gamma. HRS cells are negative for all types of Ig expression (→) whereas plasma cells are intensively labeled; normal B-cells are weakly or moderately positive.