Ocular Granulocytic Sarcoma as an Initial Clinical Presentation of Acute Myeloid Leukemia Identified on Flurodeoxyglucose Positron Emission Tomography/Computed Tomography

An 11-year-old child presented with a progressively increasing swelling in the left eye with gradual visual loss for 3 months. 2-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) was done for suspected clinical diagnosis of lymphoma. The maximum intensity projection image revealed FDG uptake in region of the left orbit, left paraspinal region in the lumbar, and multiple sites in pelvis [Figure 1a, black arrows] with low-grade diffuse FDG uptake in the marrow of vertebrae, pelvis, and bilateral proximal femur and humeri [Figure 1a, bold black arrows] - suggesting marrow involvement by disease. Transaxial PET/CT image of the left orbit revealed FDG avid large soft tissue mass (7.2 cm ×5.2 cm – maximum standardized uptake values [SUVmax] - 6.14) infiltrating the extraocular muscles, optic nerve, choroid with extraorbital causing outward, downward, and lateral displacement of the eyeball [Figure 1b, white arrow head]. The additional FDG-PET/CT revealed clinically occult lesion in the paraspinal region at L1–L2 junction [Figure 1c, long white arrow], soft tissue mass in the left S1 canal [Figure 2a and b, short black arrow], and mass in the right paraspinal region posterosuperior to sacroiliac joint [Figure 2c and d, short white arrow]. Concurrent laboratory evaluation revealed pancytopenia and high serum lactate dehydrogenase. Bone marrow biopsy was suggestive of acute leukemia. Fluorescent situ hybridization test was suggestive of acute myeloid leukemia (AML), M2 subtype. Cytogenetic studies revealed translocation, t(8,14), in 94% of cells.

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Figure 1 Maximum intensity projection image (a) reveals fluorodeoxyglucose uptake in the region of left orbit, left paraspinal region in the lumbar, and multiple sites in the pelvis (black arrows) with diffuse uptake in the marrow of vertebrae, pelvis, and bilateral proximal femur and humeri (bold black arrows). (b) Transaxial positron emission tomography/computed tomography image of the left orbit shows a large soft tissue mass infiltrating the extraocular muscles, optic nerve, choroid (white arrowhead). (c) Transaxial fused positron emission tomography/computed tomography shows a fluorodeoxyglucose avid lesion in the paraspinal region at L1–L2 junction (long white arrow)

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Figure 2 Trans-axial computed tomography (a) and fused positron emission tomography/computed tomography (b) images shows uptake in enhancing mass in the left S1 canal (short black arrow). Coronal computed tomography (c) and fused positron emission tomography/computed tomography (d) images mass in the right paraspinal region posterosuperior to sacroiliac joint (short white arrow)

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Granulocytic sarcomas (GSs) are a rare extramedullary presentation of AML and occur in about 2–8% of cases. It can precede the diagnosis of AML in 25% of cases, occurs concomitantly in 15–35% or occurs after diagnosis/at relapse in up to 50% of patients.[1] The studies have shown that presence of GS in patients with AML is associated with poor overall survival.[23] Common sites of presentation include bones, lymph nodes, skin, breast, and rarely in the gastrointestinal or genitourinary tract or in the head neck regions.[4] Ocular GS (OGS), rare in adults, is relatively common in pediatric patients with AML. Symptoms may be nonspecific and include proptosis, pain, and visual deficits. M2, M4, and M5 are the common subtype of AML associated with OGS. The most common cytogenetic abnormality associated with OGS is t(8,21).[5] There is no consensus on the optimal treatment of OGS. Few reports have shown beneficial outcomes with the addition of local external beam radiotherapy to standard chemotherapy with cytosine arabinoside.[56]

PET/CT has been previously evaluated as a noninvasive diagnostic tool for the identification of extramedullary disease in patients with AML. Although FDG uptake in GS is usually moderate, it may be variable and is relatively less as compared to patients with hematological malignancies such as Hodgkin's lymphoma or non-Hodgkin's lymphoma. In a study done by Stölzel et al. in ten patients with histologically proven GS, there was interindividual/intraindividual variation in the absolute SUVmax (range 2.5–9.3), and 1 tumor showed no significant FDG uptake (false negative). In the same study, FDG-PET/CT also identified additional extramedullary/multifocal disease in about 60% of patients.[7] Multifocal disease is usually associated with adverse prognosis.[8] The studies have also demonstrated the potential clinical utility of PET/CT in monitoring response to treatment and in early identification of relapse of extramedullary disease during induction or at the end of chemotherapy.[7910]