PMC5337863_01
Plain magnetic resonance images of the abdomen on admission. (a) Plain axial T1-weighted image of the abdomen revealed a mass in the right psoas muscle. The mass exhibited higher intensity (white arrow) than the adjacent normal musculature (asterisk). (b) The mass also showed mildly higher intensity on T2-weighted imaging than the adjacent normal musculature (white arrow). (c) The mass showed markedly high intensity on diffusion-weighted imaging (white arrow). (d) Plain sagittal T2-weighted image of the abdomen revealed an oval-shaped mass with homogenous, mildly high intensity inside the right psoas major muscle (white arrow).
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fig1
MRI of the abdomen, including the lumbar region, was performed. MRI of the abdomen revealed an oval-shaped lesion in the right psoas major muscle measuring 4 x 11 cm and exhibiting homogenous internal intensity (Figure 1).
Histopathological examination of a biopsy specimen from the right back mass. (a) Low-power view (x100) and (b) high-power view (x400) of the biopsy specimen obtained from the right back mass, stained with hematoxylin and eosin, showed diffuse infiltration of medium-sized atypical lymphocytes into the interstitium of the striated muscle. Immunohistochemical staining with (c) anti-CD3, (d) anti-CD5, (e) anti-CD10, (f) anti-CD20, and (g) anti-BCL-2 antibodies. CD3- and CD5-positive cells were interspersed among atypical lymphocytes, but CD20-positive cells were obviously predominant. These atypical lymphocytes were CD10-negative and weakly BCL-2-positive.
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fig2
Histopathological examination revealed diffuse infiltration of large, atypical cells with irregularly shaped nuclei among the striate muscle fibers (Figure 2).