|Year : 2021 | Volume
| Issue : 1 | Page : 51-53
Incidentally detected muscular sarcocystis with ewing's sarcoma: A case report of a rare combination
Kavita Somani, Pretty Singh
Department of Pathology, Apollomedics Superspeciality Hospital, Lucknow, Uttar Pradesh, India
|Date of Submission||23-Dec-2020|
|Date of Acceptance||13-Jan-2021|
|Date of Web Publication||08-Mar-2021|
Department of Pathology, Apollomedics Superspeciality Hospital, J-7/28, Sushant Golf City, Lucknow - 226 030, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Sarcocystis is an apicomplexan protozoan, such as Toxoplasma and Plasmodium. Human muscular sarcocystis infection is a rarely reported case. The rarity of the reported cases can be attributed to nonspecific symptoms and nonrecognition of the protozoa on histology. Sarcocystis infection has been catching up recognition in Southeast Asian countries. It is a food-borne zoonosis. There are more than hundred Sarcocystis spp. known and most have been isolated from muscle tissues of various intermediate hosts, including mammals, birds, and reptiles. They are parasites with dual hosts to accommodate their dual life cycles. Humans are the accidental intermediate hosts, as have been reported as intramuscular sarcocysts of unknown species. We report a similar case of 27-year-old male, who underwent wide local excision of Ewing's sarcoma of the right arm, in conjunction with which muscular sarcocystis infection was identified. We report a rare case of muscular sarcocystis in a rarer combination with Ewing's sarcoma, with no such previous case in the literature available.
Keywords: Accidental intermediate hosts, Ewing's sarcoma, humans, muscular, sarcocystis
|How to cite this article:|
Somani K, Singh P. Incidentally detected muscular sarcocystis with ewing's sarcoma: A case report of a rare combination. Apollo Med 2021;18:51-3
| Introduction|| |
Sarcocystis gets its name from “sarcomere” as it was first reported as a thread-like cyst in striated muscles of a house mouse and was initially named Miescher's tubules after its discoverer. It has now been recognized as a protozoan of the phylum Apicomplexa as the protozoa possess an apical complex structure involved in penetrating the host cells. Other apicomplexan protozoans include Toxoplasma, Babesia, Plasmodium, Cryptosporidium parvum, and Isospora belli. Previously, this protozoan infection was considered rare, due to undiagnosed cases and nonspecific symptoms. However, the incidence of human infection is rising in Southeast Asia. Histopathology is an important method for the diagnosis of muscular infection in an intermediate host.
The exact prevalence of muscular sarcocystis is still not known due to the paucity of reported cases, due to probable nonrecognition of the parasite on histology. We report a case of extra-skeletal Ewing's sarcoma with a coexistent muscular sarcocystis infection.
| Case Report|| |
A 27-year-old patient presented to our outpatient department with a gradually progressing right arm swelling. On fine-needle aspiration cytology, it was reported as a small round cell tumor and thus the patient was posted for surgical excision.
The patient underwent wide local excision on August 25, 2020, and was sent to us for frozen section reporting of margins and definitive histopathological diagnosis.
We received a skin covered tissue piece measuring 13 cm × 12 cm × 6.5 cm. Overlying skin measured 11 cm × 11 cm. Undersurface was covered with fat skeletal muscles and fascia. On cut, a grayish-white growth was identified which measured 7 cm × 5 cm × 4 cm. Cut surface showed areas of hemorrhage and necrosis [Figure 1].
Sections from the growth showed a neoplasm, composed of small to medium size tumor cells, disposed in diffuse sheets and nested patterns. Individual tumor cells displayed round nuclei, stippled chromatin, conspicuous nucleoli, and scant-to-moderate amount of cytoplasm. Brisk mitotic activity was noted [Figure 2].
|Figure 2: Low-power view displaying tumor and sarcocystis in the same field (H and E section, ×100)|
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On immunohistochemistry, the tumor cells were positive for CD99 and FLI1. Ki 67 index was high.
Thus, a diagnosis of Ewing's sarcoma was rendered.
However, a not so common finding in conjunction with the malignancy was an encysted parasite in skeletal muscle showing internal bradyzoite nuclei separated by clear internal septations. The cyst was filled with bradyzoites inside the thin cyst wall. The bradyzoites showed cresentric shapes and appeared like a “swarm of worms” [Figure 3] and [Figure 4].
|Figure 3: Encysted parasite filled with bradyzoites in a swarn of worm appearance (H and E section, ×400)|
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|Figure 4: Encysted parasite filled with bradyzoites in a swarm of worm appearance (H and E section, ×400)|
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Finally, the diagnosis of Ewing's sarcoma associated with muscular sarcocystis infection was rendered [Figure 5].
|Figure 5: Round cell tumor with high mitotic index (H and E section, ×400)|
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| Discussion|| |
The name Sarcocystis lindemanni was once proposed for all intramuscular sarcocysts in humans, but it was not clearly described, and evidence of multiple morphologically different cysts suggests that there probably are several species of Sarcocystis involved in human infections. Sarcocystosis has been reported to affect a wide age range of humans, from infancy to old age. Muscular sarcocystis infection, was once considered rare. The exact incidence of the human infestation is not known but the prevalence was found to be 21% in an autopsy study from Southeast Asia, which was done long time back.
Sarcocystis species require two hosts, a definitive and an intermediate, to complete their life cycle. The sexual reproductive stage occurs in the definitive host, which appears to be relatively species constrained. During this stage, parasite activity is limited to the intestinal tract. In contrast, the asexual reproductive stage occurs in the intermediate host and appears to be relatively less species constrained.
Humans can serve as definitive hosts, with intestinal sarcocystosis for two species acquired from eating undercooked meat: Sarcocystis hominis, from beef, and Sarcocystis suihominis, from pork. Symptoms such as nausea, stomach ache, and diarrhea vary widely depending on the number of cysts ingested but appear more severe with pork than with beef.
Humans serve as intermediate hosts [Figure 6] for Sarcocystis nesbitti, a species with a reptilian definitive host, and possibly other unidentified species, acquired by ingesting sporocysts from feces-contaminated food or water and the environment. This stage occurs in the vascular endothelium and culminates in the formation of mature muscle sarcocysts. It is a condition difficult to diagnose; due to nonspecific symptoms such as fever, headache, and myalgia.
Presumptive diagnosis is based on travel history to tropical regions, elevated serum enzyme levels, and eosinophils. However, the gold standard is identifying a sarcocyst in the muscle biopsy specimen.
The rarity of detection in histological specimens and lack of specific symptoms, are the attributing factors for nonrecognition of sarcocystis. A similar association of squamous cell carcinoma in the head-and-neck region was observed by Larbcharoensub et al. in a case report.
There is no confirmed effective antiparasitic drug for muscular sarcocystosis, but anti-inflammatory drugs may reduce symptoms.
| Conclusion|| |
We wish to discuss this present case in view of the rare cases of muscular sarcocystis infection reported from India. The present case is even rarer due to its combination with a malignancy.
Consent for publication
Written informed consent was obtained from the patient for publication of this case report and any accompanying images.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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