CTICasesPericardial and Mediastinal Soft Tissue Mass (Probable Lymphoma vs. Inflammatory Pseudotumor)
Imaging findings
A soft-tissue mass encased the right internal mammary vessels, extended through the chest wall, and formed a large, confluent pericardial and mediastinal soft-tissue conglomerate encasing the aorta, pulmonary artery, and coronary arteries, with attenuation in the 40-60 HU range. PET showed only mild metabolic activity, not markedly higher than blood pool. Percutaneous biopsy was non-diagnostic, and surgical excisional biopsy of the internal mammary component yielded collagen and fibroinflammatory tissue with only rare IgG4-positive cells, without a definitive diagnosis.
Key takeaways
A bulky, infiltrative soft-tissue mass encasing the great vessels and pericardium in this distribution should keep lymphoma at the top of the differential even when biopsy returns nonspecific fibroinflammatory tissue or shows low metabolic activity on PET, since sampling error (as can occur in bulky lymphomas with sparse malignant cells amid abundant reactive tissue) can yield a falsely reassuring pathology result. The group remained skeptical of alternative diagnoses such as plasma cell granuloma/inflammatory pseudotumor or sclerosing mediastinitis given the imaging appearance and favored repeat or more extensive tissue sampling.
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