case_images: PMC6201176_01
case_images: (a) Sagittal T2-weighted MR demonstrates a heterogenous high-signal mass
  (asterisk) located posterior to the urinary bladder (black arrow). The
  dominant mass is separated from the cervix (five-pointed star) by a small
  amount of fluid. (b) Axial T2-weighted image demonstrates most portions of
  the mass (asterisk) to be primarily high signal with relatively small areas
  of fluid. (c) Axial T1-weighted precontrast image demonstrates predominantly
  low signal intensity throughout the mass (asterisk). (d) 3 min delayed
  post-contrast T1-weighted image demonstrates persistent heterogeneously
  moderate enhancement in portions of the dominant mass (asterisk).
case_images: 10.1177_2058738418806728-fig1.jpg
case_images: PMC6201176_01_10.1177_2058738418806728-fig1.jpg
case_images: fig1-2058738418806728
case_images: The ill-defined mass did not appear to be originating from the cervix and ovaries (Figure 1(a)). T2-weighted image demonstrates most portions of the mass (asterisk) to be primarily high signal with relatively small areas of fluid (Figure 1(b)). T1-weighted image demonstrates homogeneous low-signal intensity through the whole mass (Figure 1(c)), while portions of the tumor presented heterogeneously moderate enhancement on contrast-enhanced T1-weighted imaging (Figure 1(d)).
case_images: (a) On laparotomy, the abdomen and pelvis was found to be completely occupied
  by a huge multilobate mass that were surrounded by omentum and colon. (b)
  Large amounts of amorphous, gelatinous tissue were invested within all
  compartments of the intraperitoneal spaces. (c) Pseudocapsule around the
  tumor was ruptured and tissue with whitish-/yellowish-colored appearance
  flowed out.
case_images: 10.1177_2058738418806728-fig2.jpg
case_images: PMC6201176_01_10.1177_2058738418806728-fig2.jpg
case_images: fig2-2058738418806728
case_images: On laparotomy, the mass surrounded by omentum and colon extended from the pelvic cul-de-sac to a portion of hemidiaphragm (Figure 2(a)). Large amounts of amorphous, gelatinous tissue were invested within all compartments of the intraperitoneal spaces (Figure 2(b)), but no clear site of origin was recognized. During the procedure, pseudocapsule around the tumor was ruptured and tissue with whitish-/yellowish-colored appearance flowed out (Figure 2(c)).
case_images: (a) Most of the neoplastic cells demonstrated polygonal morphology with short
  spindled shape to more rounded cells in myxoid stroma and varying amounts of
  eosinophilic cytoplasm. Furthermore, polynuclear cells and cells with
  bizarrely enlarged nuclei (arrow indicated) could be detected (HE staining;
  magnification x20). (b) IHC demonstrated a malignant spindle cell neoplasm
  positive for smooth muscle actin (Envision: magnification x20). (c) IHC
  showed strong positive staining for desmin (Envision: magnificationx20). (d)
  IHC showed moderate cytoplasmic staining for MyoD1 in
  morphologically-appearing rhabdomyoblasts (Envision: magnification x10). (e)
  IHC presented focal positive staining for ER (Envision: magnification x5).
  (f) The Ki67 proliferation index was 60%-70% (Envision: magnification
  5x).
case_images: 10.1177_2058738418806728-fig3.jpg
case_images: PMC6201176_01_10.1177_2058738418806728-fig3.jpg
case_images: fig3-2058738418806728
case_images: Furthermore, polynuclear cells and cells with bizarrely enlarged nuclei could be detected (Figure 3(a)). Immunohistochemical (IHC) analysis demonstrated strongly positive staining for smooth muscle actin (Figure 3(b)) and Desmin (Figure 3c), moderate staining for MyoD1 in morphologically appearing rhabdomyoblasts (Figure 3(d)), and focal positive staining for ER (Figure 3(e)), consistent with a diagnosis of RMS. The Ki67 proliferation index reached as high as 70% (Figure 3(f)).