We report a rare case of MS that was initially misdiagnosed as intestinal obstruction due to ectopic endometriosis. Bowel obstruction by granuloma-like lesions can be caused by Crohn’s disease, adhesions due to previous surgery, tumors, strictures related to irradiation, and ectopic endometriosis. MS can occur anywhere in the body in various ways, including as a primary lesion of AML or as a relapse after AML treatment. Nearly half of patients with MS are misdiagnosed with primary or metastatic malignancies, particularly malignant lymphomas [4]. Yamauchi et al. reported that only 53% (39) of 74 MS cases were accurately diagnosed initially. Reports indicate the difficulty of accurately diagnosis MS [4, 5]. In our case, ectopic endometriosis was suspected first because of the presence of abdominal pain associated with menstrual cycles, as well as lesions in the Douglas fossa in addition to the small bowel. MS was not included as a differential diagnosis.

Although MS is generally treated with systemic chemotherapy tailored to AML, in our case, surgery was performed to diagnose and remove bowel obstruction. Although complete resection was not achievable owing to the extent of the lesions, it might be useful to add an intraoperative pathological diagnosis of small bowel obstruction by granuloma-like lesions to determine the appropriate surgical strategy. When the intraoperative pathological diagnosis reveals a suspected hematological disease, such as MS or lymphoma, it is not necessary to aim for complete resection with a large surgical invasion; but aim for appropriate treatment without complications.

A literature search for primary MS of the small bowel between 2001 to 2023 using the keywords “primary” or “isolated” or “nonleukemic,” “myeloid sarcoma” or “chloroma” or “granulocytic sarcoma,” and “small bowel” in PubMed revealed 21 cases of primary MS of the small bowel, including our case (Table 1) [6,7,8,9,10,11,12,13,14,15,16]. All patients underwent surgical resection. Of these 21 patients, 16 received chemotherapy tailored to AML. One of the remaining five patients had no mention of postoperative treatment, four were treated with surgery only, and three of the four developed late-phase AML. Patients who received appropriate chemotherapy rarely developed systemic AML, and even those who developed it achieved complete remission. Few cases have been described in detail regarding residual lesions or complete resection, suggesting that it may not be a critical factor. Even with residual lesions at surgery, the disease can be managed effectively with appropriate chemotherapy.