Our staff consists of highly experienced practicing dermatopathologists devoted to patient-focused care.

Medical Director


Elsa Velazquez, MD
is Medical Director of MGPO  Dermatopathology Associates and is board-certified in Dermatopathology and Anatomic Pathology and is an Assistant Professor at Harvard Medical School.

Prior to joining MGPO Dermatopathology Associates, she was V.P. and Director of Dermatopathology at Inform Diagnostics, Director of the combined Tufts University/Inform Diagnostics dermatopathology fellowship program, and Assistant Professor of Dermatology and Pathology at Tufts Medical School. She also served as an Attending Physician and Assistant Professor of Pathology at Harvard Medical School/ Brigham and Women's Hospital.
Dr. Velazquez completed her pathology residency and dermatopathology fellowship at New York University Medical Center, where she also worked as an Attending Physician and Assistant Professor in the Departments of Dermatology and Pathology.

Dr. Velazquez earned her MD degree at the National University of Asuncion, Paraguay, where she graduated as Salutatorian. She also completed a residency in Anatomic Pathology at the University of Rome "La Sapieza" Italy, where she graduated "summa cum laude".

Dr. Velazquez has expertise in the microscopic evaluation of the full spectrum of skin disorders and is versed in all areas (inflammatory and neoplastic) of dermatopathology. Her research focuses on squamous cell carcinoma and precursor lesions, melanoma and other pigmented lesions and inflammatory conditions of the skin, particularly psoriasis and alopecia. She co-authored over 60 peer reviewed publications (including seminal papers in the area of squamous cell carcinoma and precursor lesions) and numerous book chapters (such as Lever's Histopathology of the Skin, Sternberg's Diagnostic Surgical Pathology, Neoplastic Dermatopathology, and Atlas of Diagnostic Oncology) and has lectured in a wide variety of national and international venues. 

Our Doctors

Laboratory Director

Timothy Quinn, MD

Timothy R. Quinn, MD, CM  is a board certified in Dermatopathology and Anatomic Pathology. He is the Laboratory Director for MGPO Dermatopathology Associates and is an Instructor at Harvard Medical School.

Prior to joining MGPO Dermatopathology Associates, Dr. Quinn was the director of Dermpath Diagnostics, New England. He was a founding member and Medical Director of DermDX Boston, and an associate Dermatopathologist at Pathology Services in Cambridge, Massachusetts. He has over 20 years of experience in the diagnosis of complex skin diseases and cancers. He is licensed and certified by the American Board of Pathology in Anatomic Pathology and the American Board of Pathology and Dermatology with special qualification in Dermatopathology.

Dr. Quinn is an honors graduate from the McGill University Faculty of Medicine in Montreal, Quebec, Canada. Following an internship in comprehensive surgery at the Toronto General Hospital, Dr. Quinn completed a residency in anatomic pathology and a fellowship in dermatopathology at the Harvard Medical School/Massachusetts General Hospital, where he studied with several distinguished dermatopathologists including the late Dr. Wallace Clark, Jr. and Dr. Martin C. Mihm, Jr. He earned an Honors Bachelor of Science Degree in Biochemistry from McMaster University, Hamilton, Ontario, Canada, and was a Rotary Foundation Scholar at University College Cork, Republic of Ireland.

Dr. Quinn is a member of the College of American Pathologists, the American Society of Dermatopathology, the New England Dermatological Society, the Massachusetts Academy of Dermatology, and the Maine Dermatology Society. He currently teaches at the Harvard Medical School, and received the Department of Dermatology Award for Excellence in Teaching 2008.

Dr. Quinn’s areas of interests include melanocytic and soft tissue neoplasia, panniculitis, and inflammatory dermatoses of the gynecological/urogenital tracts. He has published extensively in leading dermatopathology journals and has authored several chapters in academic medical textbooks.

Thomas Horn, MD

Thomas Horn, MD is Clinical Professor of Dermatology and Pathology, Harvard Medical School and practices clinical dermatology at Massachusetts General Hospital.  He is board-certified in dermatology and dermatopathology.

Previously, he served as head of the Division of Dermatopathology at the Johns Hopkins Hospital and is the former chair of Dermatology for the University of Arkansas for Medical Sciences.

Throughout his career, Dr. Horn has provided services as a dermatopathologist. He possesses expertise in the microscopic evaluation of the full spectrum of skin disorders. While at Johns  Hopkins, he established himself as an authority in the histologic diagnosis of cutaneous graft-vs-host disease and he continues to receive cases from around the world.

Professionally, he served as Secretary-Treasurer and President of The American Society of Dermatopathology.  He has lectured extensively; published nearly 100 journal publications; and co-authored textbooks such as the Primer of Dermatopathology, Dermatopathology in Systematic Diseases, and Dermatology.

Dr. Horn is recognized both nationally and internationally as an expert in his field.  His particular interests are in inflammatory conditions of the skin, especially clinical-pathologic correlation.


Julie Reimann MD, PHD is board-certified in Dermatopathology and Anatomic Pathology and is an Assistant Professor at Harvard Medical School. 

Prior to joining MGPO Dermatopathology Associates, she was Director of Molecular Dermatopathology and a Dermatopathologist at Inform Diagnostics, and an Assistant Professor in Dermatology at Tufts Medical School. She is also a former faculty member of Virginia Mason Medical Center in Seattle.

Dr. Reimann earned her MD and PhD in Biophysics from Stanford University. Her PhD work led to the discovery and characterization of a previously unknown gene (Emi1) which plays an important role in various cancers and in the mitotic and meiotic cell cycles, and culminated in numerous first author peer reviewed articles. Dr. Reimann completed her anatomic pathology residency at Harvard Medical School/Brigham and Women’s Hospital, and dermatopathology fellowship in the Harvard Combined Dermatopathology Fellowship Program.

Dr. Reimann's career has focused on the microscopic evaluation of the full spectrum of skin disorders, with particular emphasis on clinicopathologic correlation and evidence-based diagnostic dermatopathology. Her research focus is on the pathogenesis and diagnosis of melanoma and pigmented lesions, adnexal tumors, and soft tissue tumors. Dr. Reimann has published numerous peer reviewed articles, including in Nature, Cell, Nature Cell Biology, American Journal of Surgical Pathology, Modern Pathology, Human Pathology, and the Journal of Cutaneous Pathology, as well as several book chapters.

Dr. Reimann is an active member of various professional societies, including the Unites States and Canadian Academy of Pathology, College of American Pathologists, American Society of Dermatopathology, New England Dermatologic Society, Massachusetts Academy of Dermatology, Association for Molecular Pathology, and the International Society of Dermatopathology, and she has given presentations at both regional and national meetings. She also teaches dermatopathology to residents at Massachusetts General Hospital and Brigham and Women's Hospital.

Dr. Reimann's areas of interest include pigmented lesions and molecular diagnostics, inflammatory conditions of the skin, soft tissue tumors, alopecia, and adnexal tumors.

William Lin, MD

William M. Lin, MD is a board-certified dermatologist and dermatopathologist. He is an Instructor in Dermatology at Harvard Medical School.

Dr. Lin earned his bachelor’s and master’s degrees in Chemistry and Chemical Biology at Harvard College and Harvard Graduate School of Arts and Sciences, concentrating on cancer drug discovery. He received his medical degree from Yale School of Medicine and completed his internship in Internal Medicine at Massachusetts General Hospital. He is a graduate of the Harvard Combined Dermatology Residency program where he served as Chief Resident. He subsequently completed fellowship training in the Harvard Dermatopathology Fellowship Program.

Dr. Lin is interested in clinicopathologic correlation and cares for patients with general dermatologic disorders and skin cancers. His clinical and research focus centers around the pathogenesis, diagnosis and treatment of melanoma and other skin cancers. His work has been recognized by awards and grants from the Dermatology Foundation, American Skin Association, Society of Investigative Dermatology, and Affymetrix, Inc., and he has published in Nature, Nature Genetics, Journal of Investigative Dermatology and the Journal of the American Academy of Dermatology. He is a contributing author to the Dermatology section of the Pocket: Primary Care handbook for clinicians and currently serves as the Section Editor for Pigmented Lesions and Melanoma at Visual Dx, Inc.

Dr. Lin's clinical interests are: acne and rosacea, atopic dermatitis (eczema), basal cell carcinoma, cutaneous reactions to chemotherapeutic agents, general dermatology, melanoma, nevi (moles), psoriasis, skin cancer, and squamous cell carcinoma.

Mariko Yasuda, MD

Mariko Ruth Yasuda, MD is a board certified dermatologist, dermatopathologist and Instructor in Dermatology at Harvard Medical School.
Dr. Yasuda completed her internship in Internal Medicine, her residency in dermatology, and a fellowship in dermatopathology at the University of Massachusetts Medical School in Worcester, Massachusetts. While at UMass, Dr. Yasuda was awarded Intern of the Year for her clinical knowledge, empathy, and compassion and later served as chief resident during her dermatology residency. She received her medical degree from Albany Medical College in Albany, New York where she was inducted into the Alpha Omega Alpha Honor Society. As a graduate of Wellesley College, she obtained her bachelor's degree in piano performance.


Jennifer Toyohara MD

Jennifer P. Toyohara, MD is a board-certified dermatologist and dermatopathologist.
Dr. Toyohara graduated from Dartmouth College as a Rufus Choate Scholar with a major in Biology and minor in Neuroscience, and received high honors for her senior honors thesis in Neurobiology. Dr. Toyohara earned her medical degree from Columbia University College of Physicians and Surgeons in New York. While at Columbia, she was awarded numerous honors and awards, including the Lawrence J. Durante Scholarship for her community involvement and breadth of interests and talents.

After an internship in internal medicine at Lenox Hill Hospital, Dr. Toyohara completed her dermatology residency at Weill-Cornell Medical College/NY Presbyterian Hospital, where she served as chief resident and was awarded the Distinguished Housestaff Award for her exemplary all-around service to New York-Presbyterian Hospital.
Following completion of her dermatopathology fellowship in the joint program of Memorial Sloan-Kettering and Weill-Cornell/NY Presbyterian Hospital, Dr. Toyohara has split her time in both clinical dermatology as well as dermatopathology, volunteering as instructor of dermatopathology for the Roger-Williams Medical Center Dermatology Residency Program. Dr. Toyohara has been very actively involved with the Massachusetts Academy of Dermatology, sitting on the Board of Directors since 2014 and has served as Vice President since 2016.

Dr. Toyohara has published numerous articles and case reports, including in the Journal of the American Academy of Dermatology, Pediatric Dermatology, Cutis, the Journal of the European Academy of Dermatology and Venereology. She also created and moderates the Dermatopathology CPC Symposium, held during the Massachusetts Academy of Dermatology Annual Meetings.

Dr. Toyohara’s interests are general clinical dermatology and dermatopathology, with specific interest in clinicopathologic correlation.


Lyn Duncan, MD

Lyn McDivitt Duncan, MD is the Director of the MGH Dermatopathology Service, and has been a full time dermatopathologist at the MGH for over 25 years.  

Professionally, she serves on the Executive Committee and the Board of Directors of the American Society of Dermatopathology, served as Program Director of the Harvard Dermatopathology Training Program from 1993-2003, and in 1995 she developed the Harvard Dermatopathology Update CME course which continues to attract participants worldwide. Dr. Duncan is a Professor at Harvard Medical School and serves on the Advisory Board of the Harvard/MIT Health Sciences & Technology Program.

Dr. Duncan is recognized nationally and internationally as an expert dermatopathologist.  Her expertise covers all diseases of the skin.  In addition to daily routine sign out, her consultative practice focuses on cutaneous oncology, particularly melanoma and lymphoma.  She has published over 100 scholarly articles and important case reports including many Case Records published in the New England Journal of Medicine.  She has edited numerous textbooks including most recently the Atlas of Essential Dermatopathology and the Atlas of Cutaneous Lymphoma. Dr. Duncan has also contributed to International Consensus documents including the WHO Blue Books.  She is an active member of key international multidisciplinary groups that meet annually to address important issues in diagnosis and patient management in skin cancer.  Her particular interests are in cutaneous oncology and distinguishing benign mimics from malignant tumors.

Hong Wu

Hong Wu, MD, PhD is board-certified in dermatopathology, anatomic and clinical pathology.

Prior to joining MGPO Dermatopathology Associates, she was Director of Quality Assurance in Dermatopathology at Inform Diagnostics, Dermatopathologist at Beth Israel Deaconess Medical Center, Harvard Medical School, and Volunteer Pathologist with Partner in Health in Rwanda, Africa.

Dr. Wu earned her MD degree at Peking Union Medical College, and her PhD degree from University of California at San Diego, where she studied molecular biology and pathogenesis of atherosclerosis.

Dr. Wu has many years of experience in diagnostic dermatopathology in both academic and private settings. Dr. Wu has expertise in the microscopic evaluation of the full spectrum of skin disorders and is versed in all areas (inflammatory and neoplastic) of dermatology. She also teaches residents and nurse practitioners.

She is an active member of any professional societies, such as CAP, NEDS, American Society of Dermatopathology. Her areas of interest include cutaneous lymphoma, inflammatory skin diseases and melanocytic lesions. 

She has published in peer reviewed journals and has authored the chapter in vesicular bullous disease in Lever's Histopathology of the skin.