Diagnostic Electron Microscopy (EM) Unit

The Diagnostic Electron Microscopy Unit, led by Dr. G. Petur Nielsen, provides diagnostic transmission electron microscopic services to the Mass General community, and to pathologists and researchers throughout the U.S. and abroad. The transmission electron microscope (TEM) uses electrons to image tissues at much greater magnification than is possible using photons in a light microscope, allowing us to visualize in detail the many structures and organelles within cells.

Since its inception in 1975 by Dr. Ann Dvorak, then under her successor, Dr. G. Richard Dickersin, the unit has been on the cutting edge of diagnostic electron microscopy and has been involved in clinical research projects for private and outside institutions. Projects in the fields of embryology, tumor genesis, bone formation, transplantation biology, nerve regeneration, and colonic and pancreatic stem cell research have led to many significant academic contributions.

Over the years the laboratory has had a steady stream of visiting pathologists, fellows, rotating residents and medical students, many of whom have gone on to become prominent in the field of diagnostic electron microscopy. New efforts focus to enhance productivity, increase the scope and involvement in research projects and explore innovative new ways to use transmission electron microscopy in diagnostic pathology.


  • G. Petur Nielsen, MD - Director, Electron Microscopy Lab

Clinical Program

The types of tissues received by the unit consist of tumors, renal pathology (kidneys), neuropathology (skin, muscle and nerve), cytology (fine needle aspirates, bronchial and peritoneal lavages, voided urine, and pleural effusions) autopsy specimens, teaching (cases done for academic interest), research, and “other” (infectious, genetic, and metabolic diseases) specimens. Receiving less than 0.5% of the total surgical specimens coming through the Pathology Department, those that make their way to us are often the most unusual, interesting, and difficult to diagnose.


Tumor and other cases
Currently, approximately 27% of the cases are tumors and others, 21% are kidneys, 21% are neuropathology, 3% cytology, 4% autopsy, 5% teaching, and 19% research.
Renal cases
Outside referral cases consist of about 20% of the total. Sources of outside work include consults for pathologists within the department, direct submission of cases from local and outside institutions and from abroad (Canada, England, Austria, Iceland and elsewhere).
Outside renal cases account for 50% of all kidney cases and are received from local and outside hospitals.
Renal tissue from abroad is received from the Kidney Institute in Manila (Philippines), World Care (Saudi Arabia), and the United Arab Emirates.
Total number of cases
The total volume of cases has increased over 30% during the last ten years.

Electron Microscopy Innovations

The Unit has decreased turn around time for diagnostic cases to a guaranteed four business days (or two-day "rush") with the purchase of an automated tissue processor. This purchase has allowed the running of cases two or three times a week, overnight. The added overnight hours has made for better tissue fixation, infiltration and epoxy embedding for more reproducible results from run to run.

In 1993 the unit took over the electron microscopy of neuropathology cases for cost effectiveness and space reasons.

In 1999 members of the unit in collaboration with colleges at Spaulding Rehabilitation Hospital wrote and received a small equipment grant to purchase an Agfa Duo scan professional digital scanner to facilitate the transfer of images via the Internet and E-mail. Electronic images can now be sent to requesting outside institutions, pathologists, and research collaborators. The scanner has proven itself an invaluable tool in the creation of visual teaching aids and making posters for academic meetings. Additionally, traditional negatives (and X-rays) can be digitized with this scanner enabling us to archive older cases electronically.

In 2003 we retrofitted our Phillips 301 TEM with an AMT (Advanced Microscopy Techniques) 1K digital CCD camera. This innovation further decreased turn around time, saved space by allowing us to convert the traditional darkroom into laboratory space, and saved money by eliminating darkroom and associated waste disposal costs. Technologist time savings are estimated at about 20% total work time, allowing staff the opportunity to be more efficient with their time. Images are now stored on secure off site servers and easily distributed only to those on a need to know basis enhancing patient confidentiality regulations and security.

In 2009, the department purchased a new, state of the art, FEI (formerly Phillips) Morgagni TEM to replace the aging Phillips 301. The new microscope was fitted with an improved AMT 2K digital camera for superior image quality.

Academic and Research Accomplishments

Clinical Research projects have been a very important part of the Diagnostic Electron Microscopy Laboratory since its inception in 1975. The lab has contributed to innumerable clinical research projects, case studies, professional meetings and basic research. In 2000 the second edition of Diagnostic Electron Microscopy A Text/Atlas by G. Richard Dickersin M.D. was published by Springer Verlag, NY, NY. With over 1000 pages and 900 illustrations the book is a definitive tool for diagnostic electron microscopy laboratories around the world. The book was a joint effort with the Renal Glomerular Disease chapter authored by Shamila Mauiyyedi M.D., of the renal pathology group, Mass General, and the Diseases of Skeletal Muscle and Peripheral Nerve chapter authored by Umberto De Girolami M.D., Chief of Neuropathology, Brigham and Women's Hospital. The book has proven itself an invaluable tool for teaching residents and fellows the value of electron microscopy in diagnostic pathology and continues to be one of the most authoritative volumes ever published on the subject.

Ongoing clinical research projects include Renal Transplantation work in which the electron microscopy unit has been working closely with the renal pathology group (led by Dr. Robert B. Colvin M.D.), on various aspects of renal transplantation biology. Several animal models have been used to study the pathogenesis and prevention of xenograft rejection, acute and chronic humeral rejection, and the pathogenesis of chronic allograft vascular disease. Numerous publications have resulted from this ongoing work.

Other projects include collaboration with Robert W. Bunting M.D., of the Spaulding Rehabilitation Hospital Boston, MA, on the role of vitamin B12 and DNA health. Neutrophils (from peripheral blood) from patients with B12 deficiency were studied ultrastructurally using a marker for DNA strand breaks. Findings included an increase in nuclear appendages, abnormal mitochondria and eosinophil granules, and an increase in apoptotic white blood cells. These abnormalities were reversible with vitamin B12 therapy. Work on this project has resulted in two publications and two invited guest lectures to the International Congress on Amino Acids in Bonn, Germany (1999), and Vienna, Austria (2001). Work on this project continues.

New initiatives include working closely with cytopathology on procedures to effectively perform electron microscopy on extremely small samples. The hope in the future is that electron microscopy of fine needle aspirates will become routine for difficult cases. Early results are promising, especially with difficult diagnosis such as melanoma, and mesothelioma.

Teaching and Educational Activities

Electron Microscopy Conferences are given to the residents and staff of the pathology department on a regular basis. Usually, interesting cases from previous weeks are shown and discussed in which electron microscopy made or confirmed the diagnosis.

Residents are strongly encouraged to learn the basics of electron microscopy during their rotation on the renal pathology service. Residents are taught microscope manipulations (focus, magnification, and image taking) so that upon leaving the lab they have a better understanding of the ultrastructural basis of light microscopic histology.

It has been a long tradition to welcome visiting pathologists to the laboratory for varying periods of time. They have come from all over the world to experience the diversity of cases we see here and to further their knowledge of diagnostic electron microscopy. In recent years we have had these visiting pathologists appointed to Research Fellows in the EM Unit:

  • Sonia Chicano MD, Kidney Institute, Manila the Phillipines (one year)
  • Young Nyun Park, MD, Yonsei University College of Medicine, Seoul, Korea (6 months)
  • Yoon Kyung Sohn, MD, Kyungpook National University School of Medicine, Taegu, Korea (6 months)
  • Bruce Lathham, MD, Royal Perth Hospital, Australia (10 weeks)
  • Izilda Aparecida Cardinalli, MD, Universidade Estadual de Campinas, Sao Paulo, Brazil (3 months)


Additional recent and current in-house (Mass General) projects include:

  • Studies of pancreatic and colonic stem cells (Vikram Despande, MD, Mass General and Omer Yilmaz, MD, Mass General, Whitehead Institute MIT, Cambridge, MA)
  • Early bone formation (Henry Kronenburg, MD, Mass General and Christa Maes, PhD, Brussels, Belgium)
  • Pancreatic islet cells (R. Neal Smith MD, Mass General)
  • Liver and kidney regeneration/transplantation (Robert Colvin, MD, Mass General, R. Neal Smith, MD, Lynn Cornell, MD, Mayo Clinic, MI, Brad Farris, MD, Ererson Hospital, Atlanta, GA, and Erin Ochoa, MD, Mass General)
  • Ulcerative colitis (Atul Bhan, MD, Mass General)
  • Ethanol metabolism (Laposata, MD, Mass General)
  • Lipid metabolism (Mason Freedman, MD, Mass General)
  • Iimmune responses in various tissues (Stuart Houser, MD, Mass General)
  • Tumor induction in stromal cells (Ramnick Xavier, MD, Mass General)

Outside projects include work on dendritic cell lines (Jack Arbiser, MD, Emerson Hospital, Atlanta, GA), and ongoing work with Robert Bunting, MD, Spaulding Rehabilitation Hospital, Boston, MA.