Figure 2e:

Images and photomicrograph in a 1-year-old boy with alveolar rhabdomyosarcoma. MR imaging was performed after neoadjuvant chemotherapy at an outside facility and radiation. (a) Axial fluid-sensitive fat-suppressed T2-weighted sequence (3879/69) shows hyperintense intramuscular residual mass (arrow) in left soleus. (b) Axial T1-weighted (566/8.9) image shows residual iso- to minimally hyperintense mass (arrow) adjacent to skeletal muscle. (c) Axial postcontrast T1-weighted image (volumetric interpolated breath-hold examination, 8.1/4.8) shows diffuse enhancement throughout most of mass (arrow). (d) ADC map shows lack of restricted diffusion throughout mass with minimum ADC of 1.3 × 10⁻³ mm²/sec and mean ADC of 1.3 × 10⁻³ mm²/sec. (e) Coronal contrast-enhanced image obtained with DCE MR imaging (time-resolved angiography with interleaved stochastic trajectories, 3.2/1.1) 10 seconds after administration of contrast agent shows lack of early arterial enhancement in medial calf. Patient underwent radical resection of left calf alveolar rhabdomyosarcoma. Histopathologic specimen revealed complete (100%) treatment-associated fibrosis with histiocytic response and calcification. (f) Histologic evaluation (magnification, ×20) hematoxylin and eosin–stained slide shows residual damaged skeletal myocytes (brightly eosinophilic rounded cells indicated by arrows), each encircled by fibrosis and a few nonneoplastic vessels, with no evidence of residual tumor. Although anatomic images including static postcontrast sequences suggest residual neoplasm, the lack of restricted diffusion and early enhancement supports histopathologic finding of good treatment response.