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2. Contrast-enhanced chest, abdomen, and pelvis CT
CT of the brain may play a role in the staging of the diagnosis of sarcoma, but chest, abdomen, and pelvis CT is more appropriate at this point to stage the malignancy, and, if brain imaging is required, MRI of the brain would be preferable to CT for staging purposes. Lower extremity radiography is a reasonable study to perform to assess for the potential primary lesion site, as osteosarcoma arising for the knee would be a primary consideration. However, the type of sarcoma was not specified in the biopsy report (synovial sarcoma, leiomyosarcoma, osteosarcoma, etc.); therefore, the primary sarcoma location could be practically anywhere in the body, and random radiography is unlikely to be revealing in this case. 68Ga-citrate scintigraphy is occasionally used to assess diffuse lung disease or for possible infection, but does not play a role for the evaluation of presumed metastatic sarcoma. Pulmonary function testing may provide useful data, particularly as regards operative candidacy if appropriate, but would not be useful for staging presumed metastatic disease or localizing the site of the primary malignancy.
The patient underwent contrast-enhanced chest, abdomen, and pelvis CT (Figure 4) and FDG-PET imaging (Figure 5).
Figure 4. Axial enhanced thoracic CT, obtained as part of a chest, abdomen, and pelvis CT obtained for staging purposes, shows the left perihilar nodule (arrow) is associated with an irregular filling defect (arrowheads) within the left pulmonary artery.
Figure 5. Axial FDG-PET images show intense hypermetabolic activity corresponding to the filling defect within the left pulmonary artery seen at contrast-enhanced thoracic CT.
These examinations did not show features of metastatic disease in the abdomen or pelvis, nor did they show thoracic lymphadenopathy or other lung nodules, in addition to the two nodules detected at chest radiography.
Based on the CT (Figure 4) and FDG-PET study (Figure 5), what is the most likely diagnosis for this patient? (Click on the correct answer to proceed to the ninth and final page)