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Case of the Week 577

This week's very cool case was donated by Dr. Mike Feely. We haven't had anything like this one before on the blog!

The specimen below was submitted by a young woman who found this "worm" by her arm, right below her mouth, upon waking from a nap. She reported having abdominal pain with associated diarrhea for several weeks prior to presentation, but was otherwise healthy. What's the identification?

Read Dr. Pritt's blog, Parasite Wonders, and submit your answers, comments, and questions. Also, visit her website ParasiteWonders.com, which hosts an archive of classic images from cases Dr. Pritt posted going back to 2007 (in an easy-to-search "A through Z" format) and also offers a flashcard feature.

After being in formalin.
Histologic sections (H&E)
Histologic sections (H&E)

Answer to Case 577:

Planarian worm, Bipalium species, commonly known as the "hammerhead worm."

Bobbi Pritt, M.D.

Bobbi Pritt, M.D.

Bobbi Pritt, MD, MSc, is a Professor of Laboratory Medicine and Pathology and the Director of the Clinical Parasitology Laboratory at Mayo Clinic in Rochester Minnesota. She is also the Chair of the Division of Clinical Microbiology. Her research interests are in clinical parasitology, vector-borne diseases and the pathology of infectious diseases.