Subclinical chronic lymphocytic leukemia with atypical cutaneous presentation.

Chronic lymphocytic leukemia (CLL) involving skin is a rare but well-documented occurrence, mainly reported in advanced disease. In contrast, CLL presenting with skin lesions is exceedingly rare, only few reports existing to date. We report a 70-year-old man who presented with two non-pruritic, papular lesions on the lower abdomen and proximal thigh. Biopsies showed dense lymphohistiocytic infiltrates involving the reticular dermis and subcutis without epidermotropism consisting mostly of small, CD20 and PAX-5-positive B-cells expressing CD5, CD23, CD43 and BCL2. Numerous large B-cells were present in a T-cell, histiocyte-rich background. A staging bone marrow biopsy showed a clonal B-cell proliferation with typical CLL flow cytometry immunophenotyping but neither lymphadenopathy nor absolute lymphocytosis was present. Numerous B and T-cell cutaneous lymphoproliferative disorders can be associated with increased numbers of histiocytes occasionally masquerading as benign disorders. This was the case with our patient's lesions, originally interpreted as cutaneous Rosai-Dorfman disease. A high index of suspicion from both the pathologist and the dermatologist is essential in identifying these rare but probably underrecognized occurrences of early systemic lymphoproliferative disorders presenting as cutaneous lesions with an unexpected cellular composition.