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.

Case of the Week 174

The following were found in a vacant ski lodge which had not been occupied in several months. Identification? (CLICK ON IMAGE TO ENLARGE)

Answer to Case 174

Answer: Bat bugs

Congratulations to all of my readers who got this right! I thought this might be a tricky case since bat bugs share many morphologic similarities with the ever-popular bed bugs. But most of you picked up on the subtle differences between the 2 arthropods.

As Blaine points out, "Given the length of the pronotal setae, they are bat bugs, Cimex sp. Cannot differentiate further without more geographic location (C. adjunctus in the east; C. pilosellus in the west)." Here are some web sites that highlight the important differences between these 2 bugs: BUGGUIDE and BADBEDBUGS

Case of the Week 173

The following sections are from a skin biopsy of an itchy flank rash. Identification?

(H&E, 40x original magnification)


H&E, 400x original magnification


H&E, 400x original magnification

Answer to Case 173

Answer: Scabies caused by the microscopic mite Sarcoptes scabiei.

This mite burrows into the superficial layers of the epidermis and deposits eggs and fecal pellets (scybala). The diagnostic features of this case are:
1. The location within the epidermis
2. Size of mite and presence of toothlike spines on its thin exoskeleton (see below).
3. Adult and egg forms (below)





The best way to diagnose scapies is via skin scrapings (rather than biopsy). Skin scrapings can be obtained through which will produce mites with the best morphology. To obtain skin scrapings, mineral oil can be applied to the possible skin tracts followed by vigorous scraping with a sterile scalpel blade or glass slide. The material obtained should be placed on glass slides and examined for the presence of mites, larvae, and fecal pellets.

Anonymous and Neuronurse mentioned that this parasite resembles Gnathostoma spp, which also have spines on their external surface. However, Gnathostoma are uncommon in the epidermis (usually seen in subcutaneous tissue and viscera) and the spines are much smaller than those seen on the scabies mite. Gnathostoma also has different internal structures including large lateral cords. Good thought!