Sean Klepper M.D.
Stephen Lyle, M.D., ...
- Recurrent red to brown papules or plaques
- Most common on the upper extremities and trunk
- Possible association with Borrelia burgdorferi infection
- Excellent prognosis
- Nodular to diffuse lymphocytic infiltrate involving the dermis and upper subcutaneous fat
- The infiltrate is composed of small mature lymphocytes and monocytoid B-cells.
- Monocytoid B-cells are medium-sized lymphocytes with abundant clear-staining cytoplasm and indented nuclei.
- Reactive germinal centers are frequently present, and the neoplastic lymphocytes commonly encroach on the germinal centers.
- Focal to extensive plasma cell differentiation is common.
- The epidermis is characteristically spared.
- The immunophenotype is nonspecific, with positivity for pan-B-cell markers.
- If plasmacytic differentiation is present, immunohistochemical staining for immunoglobulin light chains may demonstrate kappa or lambda light chain restriction, proving the clonal nature of the process.