|
| | Diagnostic entity | Features | Immunohistochemistry/special stains |
|
| Neoplastic (monoclonal) | Marginal zone lymphoma | Plasma cells at periphery of germinal centers | CD20, CD79a, PAX5, BCL2+;
BCL6, CD10−
|
| Plasmacytoma | Large infiltrate of monoclonal plasma cells | CD79a+;
CD19, CD20− |
| Leukemia cutis (plasma cell leukemia) | Infiltrates of atypical-appearing plasmacytoid cells | CD38, CD138+;
CD20+/−;
CD19, CD49e− |
|
| Inflammatory (polyclonal) | Castleman’s disease (plasma cell variant) | Lymph nodes with hyperplastic follicles and interfollicular sheets of (lambda restricted) plasma cells | HHV-8+ |
| Pseudolymphoma | Circumscribed follicles of lymphocytic infiltrates with plasma cells at periphery; clinical correlation is paramount | Directed to rule out lymphoma, which is more likely BCL-6 and CD10+ outside follicle and BCL-2+ within follicle; Ki-67, more diffuse staining in reactive germinal centers than lymphoma |
|
| Infectious (polyclonal) | Borrelia (erythema migrans, acrodermatitis chronica atrophicans) | Perivascular lymphocytic infiltrate, rich in plasma cells | Wright-Giemsa, Warthin-Starry (silver stains) |
| Syphilis | Dense plasma cell predominant dermal infiltrate, elongated rete ridges, and endothelial swelling | Silver stains, T. Pallidum immunohistochemistry |
|
