Case of the Week 816

This week's case was generously donated by Dr. Daniel Montelong from UT Southwestern Medical Center. The patient is an elderly gentleman who underwent screening colonoscopy. Normal mucosa was found in the entire colon. However, a worm was found embedded in the cecum, measuring approximately 10 mm x 1 mm:

The worm was removed with the biopsy forceps, and biopsies from the mucosal site of worm attachment were also taken with a cold forceps for histology. The histopathology report described the presence of colonic mucosa with focal eosinophilic crypt abscess and increased eosinophils in lamina propria, in addition to the identification of the worm. Based on the histopathologic appearance from the following images, what is your diagnosis?

Answer to Case 816

Answer to the Parasite Case of the Week 816: Trichuris trichiura adult.

Our readers presented an excellent differential diagnosis based on the appearance of the nematode and its location in the intestinal tract. Even if you don't have a lot of experience with histopathologic sections, you can narrow the differential based on a few key features:

First, the gross appearance is consistent with a small nematode (10mm long according to the measurements provided, but we can also approximate the size based on the diameter of the intestinal lumen). The small size helps us narrow the differential to a few potential nematodes: Enterobius vermicularis, hookworm, Trichuris trichiura (assuming that part of the worm broke off during removal), an anisakid larva, and an immature Ascaris lumbricoides. It's great that we have 2 sequential photos in this case, showing how the tail curled up on itself, leading me to think that it might be a male nematode:

Second, we can see from the microscopy images that the worm is embedded in the colonic mucosa.

A. lumbricoides and E. vermicularis do not invade the intestinal wall, so we can rule them out, leaving us with just T. trichiura, hookworm, and anisakids in the differential.  

Lastly, the location in the cecum helps us rule out the hookworms as they are typically found in the small intestine rather than the colon. As Blaine Mathison mentioned, "Trichuris’ favorite childhood playground game is hide-in-cecum 😎" E. vermicularis also likes this location. Our job is now much easier!

But how do we make a final identification? This is where the histopathologic features play a key role:

• There are no lateral alae, so we can rule out E. vermicularis.

• There is a stichosome and bacillary band. A stichosome is a multicellular organ comprised of stichocytes (see white arrows below) that is very prominent in some nematodes, include members of the Trichinellidae and Trichuridae.

• Another very helpful feature would have been the presence of eggs. However, there are none seen in this case, possibly because the worm might be a male. However, the other features mentioned above still allow us to make a definitive diagnosis. 
• The last helpful histopathologic feature is when the embedded portion is much smaller in diameter than the portion left hanging in the intestinal lumen. As many of you know, the narrow end is the head, and this is the end that embeds itself in the intestine. The thicker end hangs free in the lumen, allowing eggs to be easily shed into the stool from the female worms.

Thanks again to Dr. Daniel Montelong for donating this great case!

Case of the Week 815

This week's case was generously donated by Dr. Jacob Rattin, a pathology resident at Cleveland Clinic. 

A traveler returning from a lengthy hiking exploration in South America presented with itching, pain, and lesions on the soles of their feet. A skin biopsy was performed with showed the following on hematoxylin and eosin (H&E):

H&E, 25x magnification

H&E, 25x magnification

H&E, 40x magnification

H&E, 100x magnification

H&E, 100x magnification

H&E, 200 magnification

H&E, 400x magnification

What is your diagnosis? 

If this is an organism and not artifactual, what structures do you think are present? Is this a male or female? 

Answer to Case 815

Answer to the Parasite Case of the Week 815: Tungiasis, caused by the flea Tunga penetrans

The following excellent description is written by Dr. Rattin:

Tungiasis is endemic in Latin America, sub-Saharan Africa, and the Caribbean. As is sadly all too common, it predominantly affects resource-poor communities. There is no standard treatment, but recommendations include surgical removal, wound disinfection, and dimeticone-based topical therapy (NYDA – a mixture of two low-viscosity dimeticones).

Tunga penetrans is the chigoe flea (with myriad other names). Gravid females lay eggs which are shed in the environment. Here, the eggs hatch into larvae, which have two stages prior to forming pupae. The pupae are in cocoons, from which the adults hatch and search for a warm-blooded host. The males and females can feed on the host, but only the females will burrow into the skin. This answers the question in the case whether this is a male or female – it is a female since it has burrowed and because of the numerous eggs that are visible. Only the posterior ends will be exposed to the environment, with their anterior end burrowed into epidermis. They can shed about 100 large eggs over a two-week period. They will then die and be sloughed off by the host’s skin. The damage to the skin can cause secondary bacterial infections, even possibly leading to sepsis. If the patient tries to remove the embedded female by themselves without sterile tools, tetanus is also a possible complication. 

The hematoxylin and eosin (H&E) stained sections showed hyperkeratosis of the overlying host skin and important features diagnostic of tungiasis. Identifiable features are the sclerotized cuticle (yellow) and tracheal rings (Figure 1), digestive tract (Figure 2), and numerous large eggs (Figure 3). The eggs are actually visible to the naked eye! These features, along with the large size of the embedded flea and the position within the epidermis help differentiate Tunga penetrans from other arthropods such as scabies and ticks that may be seen embedded within skin.  

Figure 1, H&E, 100x magnification:

Figure 2, H&E, 100x magnification

Figure 3, H&E, arrows pointing to two of many eggs. 100x magnification

Thanks again to Dr. Rattin for donating this great case!