This is a 74 year old lady who noticed a pruritic reddish skin lesion that was about the size of a dime with a midline dot that was thought to be a spider bite. She tried an antibiotic with no relief. This lesion was biopsied. She had no B-symptoms.

The morphologic findings seen in the biopsy depicted is fairly characteristic for a cutaneous extranodal marginal zone lymphoma (cENMZL). These lymphomas are often rich in background T-cells and histiocytes and may contain reactive follicles in the background with variable numbers of reactive large B-immunoblasts. While cutaneous lymphoid hyperplasia may look very similar, the infiltrative nature and the restricted plasmacytic population depicted below allow classification as CMZL.

Notably, this case was initially interpreted at the originating institution to be a possible T-cell/histiocyte rich large B-cell lymphoma. Likely, the large reactive B-lineage immunoblasts were interpreted to be neoplastic large B-cells admixed with background rich in T cells and histiocytes. Careful attention to the presence of reactive follicles and restricted plasmacytic population allows precise subclassification as cutaneous marginal zone lymphoma. Systemic staging nevertheless needs to be done in such cases.