Primary cutaneous marginal zone lymphoma with subclinical cutaneous involvement and biclonality

Primary cutaneous extranodal marginal zone lymphoma (MZL) of mucosa‐associated lymphoid tissue (MALT) represents a monoclonal B‐cell neoplasm that typically presents with papules, plaques or nodules. We describe a patient with a primary cutaneous MALT lymphoma with unusual clinical features and an unusual immunophenotype. Conventional microscopy together with immunohistochemistry and in‐situ hybridization showed the presence of lymphoma in normal‐appearing and minimally erythematous skin as well as in clinically involved skin. Furthermore, at least two distinct clones were shown, one of which had κ‐light chain restriction, and the other of which had λ‐light chain restriction. This case represents a newly described clinical appearance of primary cutaneous MZL and shows that some patients may have more than one neoplastic clone. Edinger JT, Lorenzo CR, Breneman DL, Swerdlow SH. Primary cutaneous marginal zone lymphoma with subclinical cutaneous involvement and biclonality.