Figure 1a:

Images and photomicrograph in a 14-year-old boy with synovial sarcoma. Preoperative MR imaging was performed after neoadjuvant chemotherapy with ifosfamide and doxorubicin and radiation. (a) Axial fluid-sensitive fat-suppressed T2-weighted image (2191/59) shows heterogeneous hyperintense intra-articular mass (arrow) in suprapatellar pouch extending into medial thigh. (b) Axial T1-weighted (778/11) image shows heterogeneous mass (arrow) containing hyperintense components when compared with skeletal muscle. (c) Axial postcontrast fat-suppressed T1-weighted image (volumetric interpolated breath-hold examination, 6.35/1.64) shows enhancement throughout most of mass (arrow). (d) ADC map shows restricted diffusion throughout mass (arrow), with minimum ADC of 0.7 mm²/sec and mean ADC of 1.5 mm²/sec. (e) Coronal contrast-enhanced image obtained at DCE imaging (time-resolved angiography with interleaved stochastic trajectories sequence, 3.6/1.3) 10 seconds after administration of contrast agent shows avid diffuse, early arterial enhancement throughout mass (arrows). Patient underwent radical resection of left distal thigh and medial knee synovial sarcoma. Histopathologic analysis of surgical specimen revealed minimal treatment-associated necrosis and sclerosis. (f) Histologic slide (magnification, ×40) stained with hematoxylin and eosin shows wholly viable, monotonous fibrous synovial sarcoma. Nearly every single tumor cell nucleus is viable. A few neoplastic nuclei are indicated with arrows. Both anatomic and functional MR imaging features support histopathologic findings of residual viable tumor with poor treatment response.