Not all hematological malignancies in the gastrointestinal tract are lymphoma

Abstract

Abstract Introduction/Objective Myeloid sarcoma (MS) is a rare entity that may develop in patients with acute myeloid leukemia (AML). Presentation of MS in the gastrointestinal (GI) tract is uncommon. We describe two cases of MS involving unusual sites: the stomach and appendix. Methods/Case Report A 64-year-old female consulted for fatigue and abdominal pain. A CT scan of abdomen/pelvis revealed appendicitis and CBC showed 76% blasts. An appendectomy was performed. Histologic examination demonstrated the appendiceal wall infiltrated by malignant cells, ultimately demonstrated to be positive for MPO and weak/variable CD117. In the second case, a 50-year-old male presented to the emergency department for nausea, vomiting, and elevated amylase. Esophagogastroduodenoscopy with endoscopic ultrasound demonstrated pancreatic inflammatory changes and a subepithelial nodule in the gastric fundus. Biopsy of the nodule revealed gastric epithelium infiltrated by sheets of malignant cells, ultimately demonstrated to be positive for CD34, myeloperoxidase and CD43. Results (if a Case Study enter NA) NA Conclusion MS is defined as a tumor of myeloid blasts forming outside the bone marrow. Overall, it is an uncommon entity that can occur in patients with known AML, and rarely, as the first sign of AML. Presentation of MS in the GI tract is infrequent (10%), involving primarily the small intestine (63%). The differential diagnosis includes lymphoma, poorly differentiated carcinomas, and melanomas. A review of the clinical history for AML or other myeloproliferative neoplasms should raise suspicion of MS. Expression of lymphoid markers and scant tissue for IHC studies can be diagnostic challenges, rendering B cell lymphoma as the most common misdiagnosis of MS in up to 40-47% of cases. Our two MS cases presented exclusively with GI symptoms without previously known AML and involved unusual GI sites. IHC for myeloid lineage, monocytic or myelomonocytic differentiation should be considered in specific cases. In patients without prior AML diagnosis, especially without hematologic findings, MS is a diagnostic challenge.