Hüseyin Avni Solgun,Sibel Tekgündüz,Özlem Terzi,Cengiz Bayram,Ali Ayçiçek
Myeloid Sarcoma Presenting as Brain Tumor in Pediatric Acute Myeloid Leukemia Case
Myeloid Sarcoma Presenting as Brain Tumor in Pediatric Acute Myeloid Leukemia Case

Myeloid sarcoma (MS) or granulocytic sarcoma (chloroma) is a rare extramedullary tumor composed of myeloblasts or immature myeloid cells that can destroy tissues. It usually occurs together with acute myeloid leukemia (AML). In MS, skin and orbital localization are the most common sites in childhood. Myeloid sarcoma is a rare extramedullary tumor arising from immature myeloid cells. Its relationship with acute or chronic leukemias is well known. The incidence of MS is between 3% and 5% in patients with AML. When MS and AML occur together, the prognosis for MS is much worse. M2, M4, and M5 types, which are subtypes of AML in some morphological classifications, are more closely related to MS. Although MS cases usually occur together with leukemia, they can rarely be seen in the absence of leukemia. In these cases, other solid tumors such as lymphoma, neuroblastoma, or rhabdomyosarcoma may be misdiagnosed. Although the localization of MS in children is mostly in the orbital region, it can also be involved in the skin, bone, lymph nodes, and soft tissues. Orbital MS is generally seen in children under 10 years of age and is responsible for 2%-6% of all pediatric orbital tumors. In our case in this study, tumor localization was atypical; it was located in the parietotemporal region. We present this case to update the information about MS in the literature and emphasize the incidence due to its atypical clinical location and rarity. Here, we present a 2-year-old male patient referred to our pediatric hematology oncology clinic with a left parietotemporal mass (Figure 1). The laboratory test results were for white blood cells (WBC) 71 320 × 10/L, hemoglobin 8.3 g/dL, and platelets 81 000 × 10/L, respectively. In computed tomography (CT) of the brain; a mass lesion of approximately 8 × 9 cm in size extending from the left parietotemporal lobe to the inferior, extending toward the skin/subcutaneous, causing lytic changes in the left posterior temporal bone was observed (Figure 2). A rapid peripheral blood smear (PBS) was planned to identify the leukocytosis and cytopenia. The observation of PBS reported a 5%-6% myeloid blast formation. The flow cytometric evaluation of peripheral blood showed 10% myeloblasts. A neurosurgery consultation was planned. Pulse prednisolone 40 mg/kg for the first 3 days and contiuned 30 mg/kg for 4 days have been started as a preventative treatment from brain edema. Soft tissue tumors and bone marrow metastasis or AML and granulocytic sarcoma were the initial diagnostic features. A flowcytometric peripheral blood test was reported to be 8% myeloblast. In confirmation of diagnosis AML, 20% and a higher blast percentage was needed. In this period to decrease the WBC count to safe values cytosine arabinoside treatment of 100 mg/m dosage for 24 hours was initiated. On the second day of follow-up, the WBC count was 42 000 × 10/L, and bone marrow aspiration (BMA) and cerebrospinal fluid were planned. The flow cytometric evaluation of BMA showed 10% myeloblasts (Figure 3). The genetic panel for AML was sent from bone marrow aspirate. On the 3rd day of treatment, the genetic tests reported t(8,21) positivity in this patient. The AML diagnosis was confirmed and AML Berlin Frankfurt Möunster (AML-BFM) 2019 protocol was initiated (Figure 4). The markable involution of tumoral mass from the first day to the 28th day of treatment of cerebral CT and their physical view are displayed in Figures 1A, 1B and 2A, 2B respectively. Since MS localization can be in all body parts, clinical findings in MS are very variable, especially if there is no bone marrow involvement, and this may even lead to difficulties in diagnosis. In patients diagnosed with MS, secondary solid tumors such as malignant lymphoproliferative disorders, Ewing’s sarcoma, thymoma, melanoma, round blue cell tumors, or poorly differentiated carcinoma have been reported in 25%-47% of cases. Therefore, as in our case; for differential diagnosis from other tumors and diseases; diagnostic testing for an accurate diagnosis of MS should include magnetic resonance imaging (MRI) and/or CT scanning to assess tumor size and location, morphological and flow cytometric analysis of the bone marrow, and even genetic evaluations if necessary. Especially in patients without bone marrow involvement, the diagnosis should be confirmed by effective tests such as bone marrow and peripheral blood or tumor biopsy and immunohistochemical staining. Acute myeloid leukemia treatment protocols are used in the treatment of MS, and surgery and/or radiotherapy may be preferred for symptomatic lesions or tumors causing local organ dysfunction, as in our case. Since the most common localizations in pediatric cases with MS are the skin and the orbita, an atypical locality of MS that is rarely seen in MS is presented in this case to emphasize this feature. Pamir et al in their work presented the rarity and treatment approaches of 2 extramedullary orbital MS cases without bone marrow involvement. In these cases, a total of 7 days of high-dose methylprednisolone (HDMP) therapy (3 days 30 mg/kg/day and 4 days 20 mg/kg/day) followed by AML-BFM conventional chemotherapy has been applied. For 2 cases, then, the 2004 treatment protocol was continued. As a result of HDMP treatment, we noted a significant improvement regarding eye complaints. In our case, a significant involution was detected in the parietotemporal mass in the first week after chemotherapy was started, as reported by the Pamir et al. In another study, Aslantaş et al reported that a thoracolumbar mass was detected by MRI in a 4-year-old boy who presented with a complaint of hemiparesis. In this patient, 30% of blasts consistent with AML were detected in bone marrow aspiration. The diagnosis of MS was made by a biopsy performed from the mass and pathological evaluation. In this case, complete neurologic recovery was achieved after 2 weeks of fractionated 18 Gy radiotherapy and additional dexamethasone treatment. Conventional chemotherapy was continued with the AML-Berlin Frankfurt Münster 2012 protocol. Following AML induction chemotherapy, it provided both remission and significant involution of the mass. The patient was reported to be still in remission with no residual tumor on the follow-up MRI. In our case, radiotherapy was not preferred because of the significant involution response in the tumor with dexamethasone treatment. In conclusion, conventional chemotherapy protocols for AML are still the mainstay of treatment in MS, and surgery and/or radiotherapy for symptomatic lesions or tumoral mass causing local organ dysfunction may be considered. The most common sites of application in children with MS are the skin and orbital sites. Dexamethasone and conventional chemotherapy are the first line of treatment. In our case, we presented an atypical location, an external parietotemporal mass extending to the inner part of the left parietal lobe. This settlement may require differential diagnosis even from brain tumors.