Pulmonary plasma cell granuloma (inflammatory pseudotumor) with invasion of thoracic vertebra.

Plasma cell granulomas (inflammatory pseudotumors) frequently appear as localized benign tumors of the lung in patients under 30 years of age. We describe the case of a 54-year-old woman with a plasma cell granuloma originating in the left lower lobe of lung and extending into the posterior mediastinum with destruction of the T8 vertebral body and pedicle. Distinctive histologic features included granulomatous aggregation of mature plasma cells around small blood vessels and direct invasion of the posterior mediastinum with subsequent dense fibrosis and bony destruction. Immunohistochemical studies revealed polyclonal kappa- and lambda-light chains in the proliferation of plasma cells.