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Year : 2021  |  Volume : 18  |  Issue : 1  |  Page : 51-53

Incidentally detected muscular sarcocystis with ewing's sarcoma: A case report of a rare combination

Department of Pathology, Apollomedics Superspeciality Hospital, Lucknow, Uttar Pradesh, India

Date of Submission23-Dec-2020
Date of Acceptance13-Jan-2021
Date of Web Publication08-Mar-2021

Correspondence Address:
Pretty Singh
Department of Pathology, Apollomedics Superspeciality Hospital, J-7/28, Sushant Golf City, Lucknow - 226 030, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/am.am_132_20

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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

How to cite this URL:
Somani K, Singh P. Incidentally detected muscular sarcocystis with ewing's sarcoma: A case report of a rare combination. Apollo Med [serial online] 2021 [cited 2021 Apr 11];18:51-3. Available from: https://www.apollomedicine.org/text.asp?2021/18/1/51/311006

  Introduction Top

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.[1] 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.[2] 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 Top

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.

Gross description

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].
Figure 1: Gross photograph: A skeletal muscle gray-white growth

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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 Top

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.[3] Sarcocystosis has been reported to affect a wide age range of humans, from infancy to old age.[4] 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.[5]

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.[6]

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.
Figure 6: Humans as accidental hosts form Sarcocystis species[6]

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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.[7] in a case report.

There is no confirmed effective antiparasitic drug for muscular sarcocystosis, but anti-inflammatory drugs may reduce symptoms.[8]

  Conclusion Top

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.

  References Top

Thomas JA. Human sarcocystis. J Postgrad Med 1976;22:185-90.  Back to cited text no. 1
[PUBMED]  [Full text]  
Orihel TC, Ash LR. Sarcocystis species. In: Orihel TC, Ash LR, editors. Parasites in human tissues. Chicago, Illinois: American Society of Clinical Pathologist Press; 1995. p. 32-7.  Back to cited text no. 2
Dubey JP, Speer CA, Fayer R. Sarcocystis of animals and man. Boca Raton, Fla.: CRC Press, Inc.; 1989.  Back to cited text no. 3
Lele VR, Dhopavkar PV, Kher A. Sarcocystis infection in man. Indian J Pathol Microbiol 1986;29:87-90.  Back to cited text no. 4
Wong KT, Pathmanathan R. High prevalence of human skeletal muscle sarcocystosis in south-east Asia. Trans R Soc Trop Med Hyg 1992;86:631-2.  Back to cited text no. 5
Fayer R. Sarcocystis spp. in human infections. Clin Microbiol Rev 2004;17:894-902.  Back to cited text no. 6
Larbcharoensub N, Cheewaruangroj W, Nitiyanant P. Laryngeal sarcocystosis accompanying laryngeal squamous cell carcinoma: Case report and literature review. Southeast Asian J Trop Med Public Health 2011;42:1072-6.  Back to cited text no. 7
Makhija M. Histological identification of muscular sarcocystis: A report of two cases. Indian J Pathol Microbiol 2012;55:552-4.  Back to cited text no. 8
[PUBMED]  [Full text]  


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]


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