Ileocaecal adenocarcinoma induced by Cryptosporidium parvum in dexamethasone-treated SCID mice.

A: adenomatous masses (arrow) in the intestinal lumen. SCID mouse orally infected with C. parvum oocysts and euthanatized 45 days post-infection; B: projection of a polypoid structure (PS) with focal cystic dilations (FCD) developing inside the intestinal lumen (IL). Hematoxylin & Eosin staining; C: high grade epithelial neoplasia characterized by architectural distortion and cellular atypias (*): loss of normal polarity, nuclear stratification and prominent nucleoli, associated to the presence of numerous parasites inside the glands at the surface of epithelium (arrow). Dexamethasonetreated SCID mouse infected by C. parvum after 100 days postinfection. Hematoxylin & Eosin staining; D: transmission electron micrograph showing intracellular C. parvum developmental stages inside their parasitophorous vacuole. A feeder organelle (*) adheres to the host cell membrane (HCM) on an electron-dense area, the dense band (DB).

Bar (μm) = A: 1,000; B: 400; C: 25; D: 0.4.