Superior outcome of pediatric acute myeloid leukemia patients with orbital and CNS myeloid sarcoma: a report from the Children's Oncology Group

Myeloid sarcoma: a rare case of an orbital mass mimicking orbital pseudotumor requiring neurosurgical intervention

Objective. A rare case of myeloid sarcoma (MS), previously referred to as granulocytic sarcoma or chloroma, is presented. Representing a unique form of acute myeloid leukemia (AML), MS may rarely occur in adults. Even rarer, MS may occur as the initial presentation of AML. Methods. We report a singular and illustrative case of an orbital pseudotumor mimicking mass in a 65-year-old male as the initial presentation of AML. Results. Neurosurgical intervention was required to establish the definitive diagnosis via right modified orbitofrontozygomatic craniotomy as well as to decompress the optic canal, superior orbital fissure, and orbit. Conclusion. Postoperatively, he reported decreased pain and improvement of his vision. Further examination revealed decreased proptosis and improved extraocular mobility. Pathological findings demonstrated MS. We review the literature and discuss the neurosurgical relevance of MS as the initial presentation of AML.

Orbital extra-medullary granulocytic sarcoma: clinicopathologic correlation with immunohistochemical features

Orbital granulocytic sarcoma (chloroma), a rare tumor of immature myeloid cells, has nonspecific clinical and radiological features that make it a diagnostic challenge. Light microscopy and confirmation by immunostaining aid in the diagnosis. Knowledge of this entity is important because early diagnosis and prompt treatment are associated with better prognosis. We report a series of 31 biopsy-proven orbital granulocytic sarcomas with their immunohistochemical features and review the literature.

Orbital myeloid sarcoma presenting as massive proptosis

A 10-year-old boy presented with right proptosis for 8 months. The eyeball was grossly pushed down, with diffuse corneal haze and non-reactive pupil. Systemic examination was normal. Previous investigations in another centre included a computerized tomography scan, which showed a well-defined enhancing retro-bulbar mass, a non-contributory fine needle aspiration cytology and a biopsy showing fibrocollagenous tissue with moderate lympho-monocytic infiltrate suggestive of non-specific inflammation. PET-CT scan revealed the presence of enlarged fluoro-deoxyglucose-avid cervical and mesenteric lymph nodes. Biopsy of the retro-bulbar mass was repeated in our centre. It showed fibrocollagenous and skeletal muscle tissue infiltrated by lymphoid follicles, dispersely lying lymphocytes and plasma cells, and admixed large atypical cells with vesicular nuclei, prominent nucleoli and scanty cytoplasm, strongly positive for myeloperoxidase, CD43 and CD99 immunohistochemistry. Hemogram was normal. Bone marrow aspiration/biopsy and CSF showed no evidence of acute myeloid leukemia. The child received chemotherapy in another centre and is in complete remission 6 months after completion.

Induction of histiocytic sarcoma in mouse skeletal muscle

Myeloid sarcomas are extramedullary accumulations of immature myeloid cells that may present with or without evidence of pathologic involvement of the bone marrow or peripheral blood, and often coincide with or precede a diagnosis of acute myeloid leukemia (AML). A dearth of experimental models has hampered the study of myeloid sarcomas and led us to establish a new system in which tumor induction can be evaluated in an easily accessible non-hematopoietic tissue compartment. Using ex-vivo transduction of oncogenic Kras(G12V) into p16/p19^−/− bone marrow cells, we generated transplantable leukemia-initiating cells that rapidly induced tumor formation in the skeletal muscle of immunocompromised NOD.SCID mice. In this model, murine histiocytic sarcomas, equivalent to human myeloid sarcomas, emerged at the injection site 30–50 days after cell implantation and consisted of tightly packed monotypic cells that were CD48+, CD47+ and Mac1+, with low or absent expression of other hematopoietic lineage markers. Tumor cells also infiltrated the bone marrow, spleen and other non-hematopoietic organs of tumor-bearing animals, leading to systemic illness (leukemia) within two weeks of tumor detection. P16/p19^−/−; Kras(G12V) myeloid sarcomas were multi-clonal, with dominant clones selected during secondary transplantation. The systemic leukemic phenotypes exhibited by histiocytic sarcoma-bearing mice were nearly identical to those of animals in which leukemia was introduced by intravenous transplantation of the same donor cells. Moreover, murine histiocytic sarcoma could be similarly induced by intramuscular injection of MLL-AF9 leukemia cells. This study establishes a novel, transplantable model of murine histiocytic/myeloid sarcoma that recapitulates the natural progression of these malignancies to systemic disease and indicates a cell autonomous leukemogenic mechanism.