Myeloid sarcoma in brain and optic nerve presented as a relapse of acute myeloid leukemia: A case report

Key Clinical Message Myeloid sarcoma (MS) is a rare extramedullary infiltration of acute myeloid leukemia (AML). We present a case of 19‐year‐old male with AML‐M2 who relapse with AML sarcoma in brain and optic nerve. MS as AML extramedullary relapse had a poor prognosis.

analysis of the mass confirmed the presence of a MS involving both the brain and optic nerve, with orbital involvement.Immunohistochemistry further revealed positive staining for LCA, MPO, and CD34, while CD20 and CD3 tests returned negative results.Ki67 proliferative marker showed intermediate activity.

| RESULTS AND CONCLUSION
Following treatment, the patient experienced clinical improvement and entered remission.Despite his positive developments, the patient's condition deteriorated, ultimately resulting in his death due to chemotherapy-related side effects and neutropenic fever 4 months after initiating treatment.

| DISCUSSION
MS is classified as a subtype of AML and related neoplasms by the World Health Organization. 6MS is similarly classified by the European Society for Hematology into four separate categories: [1] MS in conjunction with AML, [2] extramedullary relapse of AML, including cases after bone marrow transplantation, [3] blast phase/transformation from myeloproliferative neoplasms or chronic myelomonocytic leukemia, and [4] isolated MS, occurring without a history of myeloid dysplasia and with normal bone marrow aspirate findings.
The incidence of central nervous system (CNS) involvement in MS is relatively rare, 7 accounting for only 0.4% of cases involving cranial bone marrow, vertebrae, or orbital bones.Its migration to the brain parenchyma is attributed to the disruption of the blood-brain barrier. 8,9hile orbital involvement as an initial manifestation of AML is uncommon, it is less than 3% of cases. 10In our case, brain MRI revealed a heterogeneous mass measuring 9 × 7.5 × 3 cm in the left temporal region, extending into the left sphenoid wing and causing destruction of the pilgrims.The mass compressed the left middle cerebral artery and bulged into the left cavernous sinus (Figure 1).MS can sometimes express B-cell antigens (CD19 and CD79a), which may lead to misdiagnosis as CNS lymphoma.However, in our case, immunostaining confirmed AML with myeloperoxidase (MPO) positivity.
Treatment approaches for MS lack consensus due to its rarity and limited randomized controlled trials (RCTs).Therapeutic decisions are influenced by factors such as tumor location, the timeline of MS occurrence (before AML onset or AML relapse), patient age, and performance status.Chemotherapy, surgery, radiotherapy, allogeneic hematopoietic stem cell transplantation (allo-SCT), targeted therapy, and immunotherapy are available therapeutic options. 10Surgery plays a vital role in relieving mass effect symptoms, confirming diagnosis, and debulking large-sized MS before initiating systemic therapy. 3In cases of isolated MS with inadequate response to chemotherapy or when rapid relief of vital function impairment is necessary, radiotherapy may be recommended. 1,10In our case, we opted for neurosurgical surgery utilizing the FTOZ approach, followed by an induction chemotherapy protocol involving high-dose cytarabine (1.5 g/m 2 ).Cytarabine has a good outcome in MS.
The prognosis of MS remains uncertain due to limited available data.However, it is generally acknowledged that MS occurring concomitantly with AML or as a relapsed AML is associated with a poor prognosis. 11atients who received chemotherapy showed better prognosis compared to those who did not. 12The life expectancy of individuals with MS varies based on several factors like age, performance status, and location of the disease, with a reported 5-year survival rate of approximately 24%. 12,13Disease relapse and infections are the most common causes of mortality in MS patients, in our case the patient died with infection after 6 months from diagnosis MS.
In our case, the patient developed MS in multiple organs 3 years after achieving CR from AML, and unfortunately, his condition rapidly deteriorated within 6 months of chemotherapy protocols.This highlights the challenges associated with MS and emphasizes the need for further research and advancements in treatment strategies to improve patient outcomes. In

F I G U R E 1
Brain MRI (T1W, T2W, and FLAIR): A heterogeneous mass measuring 9 × 7.5 × 3 cm in the left temporal region, extending to the wing of the sphenoid and causing destruction of the lateral wall of the pilgrims, compressing the middle cerebral artery and infiltrating in the cavernous sinus.F I G U R E 2 Brain MRI after frontotemporal-orbit zygomatic (FTOZ) surgery and after resection the mass.
summary, MS can occur in patients with AML who have been in CR, and can manifest in various organs.Awareness of MS in various organs in relapsed AML is essential, and this diagnosis demands further individualized treatment due to very high mortality risk.