Presentation
Shortness of breath.
Patient Data
There is asymmetric abnormal elevation of the right hemidiaphragm. There is slight blunting of the costophrenic angle and minimal fluid in the right minor fissure.
There is a moderate-large right pleural effusion. There is slightly irregular pleural thickening in the right lung base.
There is a large heterogenous fairly well-defined but slightly lobulated retroperitoneal mass. It is anterior to the vertebral bodies without obvious extension into the neural foramina. It extends to the right posterior medial pleura and is posterior and to the right of the distal thoracic aorta and esophagus. The inferior extent of the mass is at the level of the midpole of the right kidney. It causes anterolateral displacement of the IVC. The mass encases and displaces the aorta, as well as the takeoff of the celiac axis. The mass straddles the superior mesenteric artery.
At the level of the renal arteries, the mass is eccentric and more to the right of midline however, it is also seen posterior to the aorta and posterior medial to the midportion of the left renal artery. There is narrowing of the right renal artery as it courses between the mass posteriorly and the IVC anteriorly.
The previously described mass demonstrated high FDG avidity, with the regions of the highest SUVmax at the superior and inferior portion of the mass.
No focal uptake elsewhere throughout the chest or abdomen/pelvis to suggest focal metastasis.
Case Discussion
This is a case of a retroperitoneal alveolar rhabdomyosarcoma.
The patient underwent a CT-guided core biopsy. Histopathology revealed scattered and clustered malignant cells with a high nuclear-to-cytoplasmic ratio, irregular chromatin, and irregular nuclear membranes. The atypical cells were positive on immunohistochemical stains for myogenin and desmin. Similar-appearing cells were identified within the right-sided pleural collection. Cytogenetic studies detected a PAX3-FOXO1 fusion. Further workup of the patient's bone marrow revealed infiltrative disease.
At the time of diagnosis, she was found to have metastatic sites including the pleural fluid, pleura, mediastinal lymph nodes, bones, and bone marrow. Taken together, this represents Stage 4, Group IV, high-risk disease.
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