Needle biopsy diagnosis of solitary amyloid nodule of the lung

Solitary amyloid nodule of the lung is an unusual form of localized amyloidosis which is rarely diagnosed prior to surgical resection. This report describes a case of solitary amyloid nodule of the lung which was suggested prospectively on the initial needle biopsy. The histologic and cytologic features of the lesion appear to be characteristic and may allow a definitive diagnosis to be made on needle biopsy. The differential diagnosis from necrotic tumor and medullary carcinoma is described. The subsequently resected nodule was studied by both electron microscopy and immunofluorescent techniques. Immunofluorescent staining failed to confirm an origin of the lesion from a single clone of plasma cells.