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.
(Unstained, 100x original magnification)
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.
Here is a special case in honor of Valentine’s 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?
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.
In December’s issue of the American Journal of Clinical Pathology there is an interesting editorial by Dr. Mark Wick that discusses Pathology 2.0 in reference to two articles in the journal. In summary, I think he feels there are uses in place for education and e-publications that are suitable and practical but thinks there are more serious considerations related to patient care, online communities related to diagnosis and/or treatment and patient privacy and security. A brief look at his website (see link above) I think emphasizes these points and makes use of educational and informational services without being directly interactive with a patient or another health care provider/pathologist.
He concludes in his editorial:
“Where, then, does this leave the status of Web 2.0 with respect to medical issues? One may appropriately state that its potential for education and practice enhancement is real and considerable. It is also true that electronic publications of scientific data are easier than ever and more widely disseminated than hard-copy contributions. However, definite problems exist regarding the veracity of some e-articles in medicine, proliferation of “charlatanesque” entries in the electronic medical literature, misconceptions about the production of “personalized” e-medical data, and the lack of compatibility and accessibility of computerized information from one medical system to another. These issues must be resolved before Internet-centered facts can be integrated confidently into diagnostic and therapeutic paradigms.”
The following H&E stained histologic sections are from a rectal abscess in a 5 year old boy. Identification?
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