Case of the Week 156

A colon biopsy from a patient with dysentery is received. On endoscopy, multiple ulcers in the rectum are noticed. Diagnosis?

Modified phosphotungstic acid hematoxylin stain (PTAH), 400x original magnification
(note, this preparation stains RBC's black)


Modified phosphotungstic acid hematoxylin stain (PTAH), 1000x original magnification
(note, this preparation stains RBC's black; see arrows)