A combination of abnormal immunoarchitecture and reproducible clonal bands identifies the biologic nature of cutaneous B-cell infiltrates.

In the multiparametric evaluation of cutaneous B-cell infiltrates (CBIs), immunoarchitectural features have been underused, and B-cell clonality alone has limited clinical usefulness. Our aim was to assess the usefulness of immunoarchitectural abnormalities (IAs) and clonality in the diagnosis of CBIs. On 39 CBIs, immunohistochemistry was performed using anti-CD45, anti-CD45RO, anti-CD3, anti-CD20, anti-CD21, and anti-CD35, and polymerase chain reaction was used to detect immunoglobulin heavy chain rearrangement. There were 33 cutaneous lymphoid hyperplasias (CLHs) and 6 cutaneous B-cell lymphomas. IAs were present in 9 lesions and clonal bands in 14 lesions. In 6 cutaneous B-cell lymphomas, IAs were associated with pure and reproducible clonal bands. IAs in 3 CLH lesions with a superficial infiltrate were not associated with clonal bands. Clonal bands in 8 CLH lesions without IAs were not reproducible from deeper sections; furthermore, in 5 of 8 cases, these were present against a background smear. A combination of IAs and clonality is a useful adjunct in the diagnosis of CBIs.