Electron microscopy of needle biopsies from cancer patients with unknown primary tumors

: The aim of the present study was to evaluate the diagnostic value of electron microscopy (EM) performed on Surecut biopsies from patients without known primary tumour. The material consisted of 108 consecutive biopsies, obtained over a period of two years, from patients with tumour(s) in the liver or lymph nodes (on the neck, in the axilla or retroperitoneum). From each patient fine needle aspirations and Surecut biopsies for light microscopy and electron microscopy were taken. Only biopsies in which material for both electron microscopy and light microscopy was sufficient were included (60%). Immunohistochemical reactions were performed on paraffin sections when indicated. Final diagnoses were confirmed on surgically removed specimens and/or autopsies. Electron microscopy was necessary for obtaining the final histological diagnosis in 15% of the cases. It is therefore recommended to obtain additional ultrasound guided biopsies for EM from cancer patients with tumours in the liver or lymph nodes in cases where the primary origin of the tumour is unknown.