There is no pulmonary embolus (is there ever?!). There are lesions in the liver (multiple other lesions were present), nodes at the right hilum and multiple lesions in the lungs. All of the lesions demonstrate similar constituent densities. There are large areas in almost all lesions of macroscopic fat. The lesion in the liver does look very aggressive prompting thoughts this may be a hepatocellular carcinoma. Indeed HCC and adenomas in the liver may have fat within them. However, it would be extremely unusual for all the metastatic lesions from a HCC to contain so much fat. Other solid lesions that may contain fat might also include germ cell tumours and sarcomas (particularly liposarcoma). Other rarer lesions include angiomyolipomas and deposits in Gauchers disease, however as we will see these do not fit with the pulmonary appearances.
The pulmonary lesions are variable. Several lesions - like the lesions in the left upper lobe and the left lower lobe appear discrete and consistent with intrapulmonary metastases. However, others however appear more unusual like the tubular lesion in the posterior segment of the right upper lobe. This lesion is fat containing just like the other lesions. The possibilities for this lesion might include an endovascular or endobronchial abnormality. The presence of small buds on the side of this tubular opacity and of other clustered nodules in other areas of the lungs suggests endobronchial disease spread.
There are limited causes of multiple peripheral endobronchial lesions. These might include polyposis, granulomas (tuberculous or sarcoid), carcinoids, and metastatic lesions from renal cell, melanoma, breast and sarcomas. Of these only sarcomas are fat containing. Therefore, the only diagnosis that optimally fits is metastatic liposarcoma - conveniently the correct response!
Teaching Point: Remember to always look at a lesion in terms of size, shape, contours, location and density.