Transmission electron microscopy of fine needle aspiration biopsies of metastases. Accuracy of both techniques as established by biopsy diagnoses.

Objective: To determine the accuracy of fine needle aspiration biopsy in establishing the primary on cytology and on cytologic and electron microscopy examinations using tissue biopsy as the gold standard.

Study Design: A retrospective study of 96 nonrandomly selected cases of metastases with an unknown primary was carried out. Tissue biopsy was performed subsequently for confirmation.