Aggressive mediastinal amyloidosis mimicking malignancy: a case report

Amyloidosis is characterized by extracellular protein fibril deposition. Light-chain (AL) amyloidosis may be associated with plasma cell dyscrasias. Isolated mediastinal involvement is exceptionally rare and may mimic malignant tumors.

A 69-year-old woman presented with a progressively enlarging anterior chest wall mass caused by an invasive mediastinal lesion. Biopsy revealed amyloid deposition. She underwent bilateral thoracotomy, sternectomy, en-bloc chest wall resection, and reconstruction. Final pathology confirmed AL amyloidosis associated with a kappa-restricted plasma cell neoplasm. Subsequent hematologic evaluation demonstrated active multiple myeloma.

Mediastinal amyloidosis may present as a locally aggressive pseudotumoral mass mimicking malignancy. Histopathological confirmation is essential for diagnosis. The association between AL amyloidosis and plasma cell neoplasms may create additional diagnostic challenges and should be considered even in apparently localized thoracic presentations.

This case highlights the diagnostic and therapeutic challenges of mediastinal AL amyloidosis with aggressive pseudotumoral behavior. Comprehensive hematologic evaluation should be performed early in all patients with localized thoracic AL amyloidosis to exclude occult plasma cell dyscrasia. Radical surgical resection may be justified in selected patients presenting with extensive local invasion and suspicion of primary thoracic malignancy. Long-term multidisciplinary surveillance remains essential because systemic progression may occur despite apparently localized initial disease.