Monday, February 22, 2010

Case of the Week 106

The follow are images of an unstained intestinal biopsy that was "squashed" between 2 slides. Please identify the objects present. They measure approximately 180 microns in greatest dimension. (CLICK ON IMAGES TO ENLARGE)

(Unstained, 100x original magnification)

(Unstained, 200x original magnification)

(Unstained, 200x original magnification)

Sunday, February 21, 2010

Answer to Case 106

Answer: Schistosoma mansoni eggs

This case seemed to generate a lot of enthusiasm from the audience. Thank you all for the great comments! The eggs shown here are classic for S. mansoni, with their large size (>150 microns largest dimension) and classic lateral spine.

Chris C. asked how I thought to do the squash preparation on this tissue. The answer is that this tissue was submitted specifically to look for Schistosoma eggs. As you can imagine, this is a rare request when you practice in an area that does not have endemic schistosomiasis. However, we do on occasion receive rectal biopsies in microbiology for this technique. It's important that the tissue be sent fresh, since fixed tissue will not squash easily, and does not provide a good preparation.

If tissue has already been placed in formalin, then it is best to submit it to surgical pathology. Unfortunately, you then get a lot of fixation artifacts, and the eggs become very distorted, as seen below:

By looking carefully, you still may be able to find a lateral spine. But be careful about calling 'spines' when all you are seeing are collapsed, angulated eggs. You'll want to be sure that you are seeing a well defined spine in the expected position. Here is a really good example of a lateral spine that survived fixation, dehydration, and sectioning:

Monday, February 15, 2010

Case of the Week 105

Here is a special case in honor of Valentines day. The following section of lung was removed due to the presence of a nodule that mimicked a lung carcinoma. However, on sectioning and H&E staining, the following was seen. Identification?

Bonus question - what does this case have to do with Valentines day???

Sunday, February 14, 2010

Answer to Case 105

Answer: Dirofilaria immitis; the Dog Heartworm

Congratulations to everyone who wrote in with the correct answer to this case!

Dirofilaria spp. cause both subcutaneous and pulmonary infections in humans, with D. immitis being largely responsible for the pulmonary infections in the U.S. and worldwide. In dogs, the adult worms live in the right side of the heart and cause debilitating disease. The adults produce unsheathed larvae which circulate in the blood and are transmitted to other hosts through the bite of an infected mosquito. Humans are accidental hosts that also acquire infection through a mosquito bite. However, the worms cannot live in the human heart and quickly die and are passively transported to the lungs where they wedge in a small vessel and produce an infarct. Eventually the lesion heals as a granulomatous coin lesion which can mimic a primary or metastatic tumor. It's easy to forget that there is filarial disease in the U.S.!

On resection, the worms are found in various stages of degeneration with a surrounding inflammatory response. They can be recognized by their size (150 - 300 microns in diameter) and thick multi-layered cuticle with lateral internal cuticular ridges (arrows, image below). The internal organs degenerate quickly and are more difficult to identify.

To demonstrate the variable appearance of Dirofilaria spp. in tissue, here a number of other images from different cases. The appearance of the internal structures are variable, but note the internal cuticular ridges in all cases.

Most of you realized the Valentine's Day connection with the Heart worm. Maybe next year I'll be able to find a fun heart-shaped cross-section of a worm for you.
Thank you for writing in and leaving your comments!

Monday, February 1, 2010

Case of the week 104

The following H&E stained histologic sections are from a rectal abscess in a 5 year old boy. Identification? (CLICK ON IMAGES TO ENLARGE)

Answer to Case 104

Answer: Pinworm (Enterobius vermicularis eggs.

A few of you noticed that I gave the answer away on the close up image! Thanks for writing in to let me know and share your thoughts.

As you all probably know, this is an extremely rare presentation of pinworm infection. Typically, deposition of eggs by the female work in the perianal skin folds causes intense itching. It is only when the worm and/or eggs ends up in a place where they shouldn't be (e.g. genital tract, colon diverticulum or fissure) that an abscess can form, and complications arise, such as seen in this case.

The diagnosis is made by identifying the characteristic eggs, measuring approximately 50-60 microns in greatest dimension.

Salbrent had asked: "Can you tell if this is recent infection or an older one?"

I believe this manifestation (the abscess) is acute, since the inflammatory response consists of neutrophils, and there is no evidence of granulation tissue or fibrosis. As far as the infection itself however, I'm not sure if it's possible to say how long it's been going on. The adult worms only live for a few months, but autoinfection is common, so it's possible that the infection has been around longer than a few months.