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Abstract

Background: Myeloid sarcoma (MS) is a rare malignant neoplasm composed of myeloid blasts occurring at an extramedullary site. In nearly half of the patients, it is misdiagnosed initially, the most common being lymphoma. Here, we reported two cases of MS with monocytic differentiation, morphologically mimicking lymphoma. Case presentationCase 1: A 62-year-old female with 6 year history of chronic myelogenous leukemia (CML), presented with one month history of central nervous system (CNS) symptoms. A magnetic resonance imaging (MRI) scan showed several bilateral frontal and left parietal dural based lesions. Intraoperative consultation for the biopsy from the left frontal dural based lesion favored hematopoietic neoplasm. A limited negative lymphoma panel excluded lymphoma by flow cytometry. MS was diagnosed on the excised left frontal dural based lesion. BCR-ABL1 fusion was detected by fluorescence in situ hybridization (FISH). Intrathecal chemotherapy, however, showed no improvement. Case 2:A 29-year-old female with no significant past medical history presented with two month history of fatigue, fever, night sweats, weight loss (10lb in one month), and multiple enlarged lymph nodes. MS was diagnosed on the excised left anterior cervical lymph node that was initially thought to be a large cell lymphoma though. A concurrent bone marrow biopsy showed cytogenetically-normal AML with monocytic differentiation and mutated FLT3 tyrosine kinase domain. After systemic chemotherapy, no residual acute leukemia was detected. In addition, the sizes of the enlarged lymph nodes were significantly decreased. ConclusionWe reported two cases of MS with monocytic differentiation, morphologically mimicking lymphoma. One case was a blastic transformation of CML presented in CNS. The other case was MS with concurrent AML presented in lymph nodes. Systemic chemotherapy is the recommended treatment for MS in addition to surgical resection, if surgical resection is necessary.