Isolated delayed metastasis to the talus from Ewing’s sarcoma

Posted By Lena Naffaa
Isolated delayed metastasis to the talus from Ewing’s sarcoma

Bone metastasis to the hands and feet, known as acrometastasis, is a very rare finding and tends to be associated with extensive metastasis. The patient is a 14-year-old girl who was diagnosed with a large chest wall ES arising from the right 6th rib at the age of 7 years. Workup for metastatic disease using bone scans, PET-CT scans, and CT scans of the chest and abdomen was initially negative and throughout treatment as well. At the time of local control she was found to have complete response with no evidence of residual disease. Periodic follow-up with enhanced CT scans of the chest and abdomen, chest MR imaging, and bone scans confirmed that she remained disease-free throughout 7 years after end of therapy. The patient currently presented with a 2-week history of left ankle pain of insidious onset, without swelling or erythema, and with no other associated systemic symptoms. There was no history of trauma or other precipitating factors. On physical exam, she had mild tenderness at the anterolateral aspect of ankle and sinus tarsi, with limited motion of the subtalar joint due to pain. MRI of the ankle and foot showed a lesion at the head and neck of the talus (Figure 1A-C). This was of low signal intensity on T1-weighted images (Figure 1A), heterogeneously high signal on short-tau inversion-recovery (STIR) sequence (Figure 1B), and showed heterogeneous enhancement following gadolinium IV contrast injection (Figure 1C). There was mild enhancing edema in the surrounding bone marrow and soft tissues, mainly at the sinus tarsi. Focal cortical disruption was present. Non-enhanced CT scan was then obtained (Figure 2A-B) and showed a well-defined lytic lesion with thick trabeculae and a sclerotic rim. Focal cortical disruption was present (Figure 2A). CT-guided core biopsy of the talar lesion was then performed showing marrow spaces invaded by neoplastic cells, most of which appeared necrotic with an undifferentiated phenotype and uniform cytology. Overall findings were typical of ES. Whole body PET/CT with 18-Fluoro-deoxyglucose (FDG) for metastatic workup was then performed and showed increased radiotracer uptake at the level of the talar lesion with a mean standardized uptake value (SUV) of 1.72 and maximal SUV of 2.4 (Figure 3). However there was no evidence of active disease elsewhere in the body. Figure 1: MRI of the left ankle and foot: (A) sagittal T1-weighted; (B) sagittal short tau inversion recovery (STIR); (C) coronal T1-fat saturation following with IV gadolinium administration. A lesion is seen involving the head and neck of the talus, showing low signal intensity on T1-weighted (arrow) (A), heterogeneously high signal on STIR (arrow) (B), and significant heterogeneous enhancement following IV contrast injection (C). Mild enhancing bone marrow edema is noted around the tumor in (C) with soft tissue edema surrounding the talus and etending into the sinus tarsi (arrow). Figure 2: CT scan of the foot: axial (A) and sagittal reconstru

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