Extranodal marginal zone lymphoma presenting as a skin-based breast finding detected on screening mammography

Extranodal marginal zone lymphoma (EMZL) of the breast is rare and may mimic benign skin lesions at screening. We report a 72-year-old woman with a new superficial mass on screening mammography. Tangential views and ultrasound localized the abnormality to the dermis/subdermis, and ultrasound-guided biopsy revealed a low-grade B cell lymphoma with plasmacytic differentiation. Staging with PET/CT, a skin punch biopsy of a cutaneous shoulder lesion, and bone marrow biopsy confirmed disseminated disease, consistent with stage IV EMZL. This case underscores practical imaging steps, strategies, and differential diagnostic considerations to correctly identify skin-based findings and avoid misclassification. When appearances are new or atypical, particularly without a visible cutaneous correlate, tissue sampling is warranted to exclude malignancy, including dermal lymphoma.