Neoplastic epithelial cells in a subset of human thymomas express the B cell-associated CD20 antigen.
A series of 36 human thymomas have been immunohistochemically analyzed using a panel of antibodies recognizing B-cell markers including CD20. Most thymomas exhibiting the cortical pattern, according to the criteria of Marino and Muller-Hermelink, were characterized by areas of medullary differentiation containing variable numbers of CD20+ B lymphocytes, thus mimicking the medulla of normal thymus. On the other hand, B cells were absent or rare in thymomas recognized as mixed using the same morphological criteria. Surprisingly, we observed in most mixed thymomas variable numbers of CD20+ spindle cells, characterized by long slender processes. Using double-marker analysis we could demonstrate the epithelial nature of these cells (expression of keratin and lack of lymphoid and B-cell-related markers). The immunoreactivity of thymoma epithelial cells with L26, an antibody widely used in the characterization of B-cell lymphomas, can represent a drawback of practical relevance in the differential diagnosis of mediastinal tumors.
Chilosi
M
M
Istituto di Anatomia Patologica, Università di Verona, Italy.
Castelli
P
P
Martignoni
G
G
Pizzolo
G
G
Montresor
E
E
Facchetti
F
F
Truini
M
M
Mombello
A
A
Lestani
M
M
Scarpa
A
A
D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000032:analysis*; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis*; D001402:B-Lymphocytes / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D013945:Thymoma / Q000276:immunology* / Q000473:pathology; D013953:Thymus Neoplasms / Q000276:immunology* / Q000473:pathology
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte