Fine-needle aspiration cytology of amyloid associated with nonneoplastic and malignant lesions.

To assess the value of fine-needle aspiration (FNA) cytology for the diagnosis of amyloid, we retrospectively studied all FNA cases diagnosed as having amyloid during a 6-yr period (1990-1996). FNA was performed on both superficial and deep locations. A total of 6 cases containing amyloid was studied, including primary medullary thyroid carcinoma, metastatic medullary thyroid carcinoma to a vertebrae, multiple myeloma, squamous-cell carcinoma of the lung metastatic to a hilar lymph node, primary pulmonary amyloid, and amyloid tumor in a vertebral body in a patient with primary systemic amyloidosis. Despite the location or disease association, the cytologic appearance of amyloid in all cases was similar. On Diff-Quik stain, amyloid appeared as amorphous, irregular, waxy basophilic to metachromatic clumps of material. Papanicolaou stain revealed cyanophilic to organophilic clumps of material with occasional prominent fissures. In all 6 cases, amyloid was confirmed by Congo red stain and in 3 cases by a thioflavin T stain. In 4 of the 6 cases (67%), amyloid was associated with an underlying malignancy. In 3 cases malignant cells were admixed with the amyloid, and in another case malignancy was present at a distant site. We conclude that FNA biopsy is a helpful initial procedure for the evaluation of patients with amyloid deposits. The clinical implications of amyloid found in any particular body site include both benign and malignant conditions. The presence of an associated neoplasm must be especially considered in the differential diagnosis of amyloid deposits.