Case of the Week 177

The following images are sections of a formalin-fixed paraffin-embedded gastric biopsy. No further history is available.
(CLICK ON IMAGES TO ENLARGE)

H&E 40 times original magnification


H&E 100 times original magnification


H&E 400 times original magnification

H&E 400 times original magnification

H&E 40 times original magnification


H&E 100 times original magnification


H&E, 400 times original magnification


Trichrome stain, 40 times original magnification


Trichrome stain, 200 times original magnification


Trichrome stain, 400 times original magnification


How would you sign this case out?

Answer to Case 177

Answer: Worm causing anisakiasis; either Pseudoterranova decipiens or Contracaecum spp.

This diagnosis is based on:
1. The size of the worm (note the size compared to the glands in the gastric mucosa

2. The characteristic location (embedded in gastric or intestinal mucosa
3. The presence of Y-shaped lateral cords on a broad base (see image below). The broad base of the lateral cords excludes Anisakis spp., although this is in the initial differential diagnosis.


For images of what this worm looks like in fish flesh, take a look at the previous weeks' cases:
Frozen fish: Case 140
Cooked fish: Case 16

Also, here is a case where the worm was removed from the fish. This is what might get submitted to the microbiology lab for identification:
Case 157

Case of the Week 176

The following objects were seen in cross-section in an appendix from a 14 year old girl with abdominal pain. Identification? (CLICK ON IMAGES TO ENLARGE)

(H&E, 40x original magnification)


(H&E, 100x original magnification)


(H&E, 200x original magnification)

(H&E, 40x original magnification)


(H&E, 100x original magnification)


(H&E, 200x original magnification)

Answer to Case 176

Answer: Enterobius vermicularis (pinworm) cross-sections

This is a classic histologic appearance of E. vermicularis in cross-section. The diagnosis is made by identification of the lateral alae (singular=ala, from the Latin meaning "wing"). Indeed, you can see why these longitudinal ridges on either side of this roundworm's body have been likened to wings.

Other features include well-developed platymyarian-type musculature (Body musculature consisting of cells not protruding individually into Pseudocoelom), thick muscled esophagus, and thick nucleated intestine; features seen in many intestinal nematodes (round worms).

Some of these features are shown in Case of the Week 88

Thanks to everyone for writing in!

Case of the Week 175

The following objects were seen in unstained fluid aspirated from a liver cyst and sent to microbiology. The beautiful images were taken by Heather A. Identification?

Answer to Case 175

Answer: Echinococcus spp. protoscoleces

Shown here are multiple protoscoleces (larval tapeworms) of Echinococcus spp. The most common species to infect humans is Echinococcus granulosus, but E. multilocularis and less commonly, other species, may also cause human infection. Note that one larva has an everted protoscolex (below).


Based on the appearance of the everted protoscolex (above), you can see how this larval form will mature into the adult Echinococcus worm in the definitive canid host:

Adult Echinococcus granulosus worm


Higher magnification reveals the hooklets of the scolex, used to attach to the intestinal tract of the definitive host.


In echinococcosis, humans and herbivores are the intermediate host and are infected with the larval forms, whereas members of the Canidae such as wolves and domestic dogs are the definitive hosts and are infected with adult tapeworms.