Answer: Cross-sections of Enterobius vermicularis adults in the duodenum. Although this is an unusual location for this worm, the characteristic lateral alae and features of an adult worm (internal organs including intestine and testes) allow us to make the diagnosis. E. vermicularis is the only adult worm found in humans that has lateral alae (although various larvae may also have lateral alae).
From Blaine Mathison:
While the duodenum is an unusual
place to find this worm,
the morphologic features
shouldn't cause you to squirm
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