The differential for a low or fat density nodes in the retroperitoneum would reasonably include metastatic testicular tumour, tuberculosis, Whipple’s, MAI, TB, nerve sheath origin tumours and fat containing sarcomas. Testicular metastatic disease, with the rare exception of scrotally invading tumours, would not involve the inguinal regions as lymphatic drainage is along the blood supply to the retroperitoneum at the level of the renal veins. The presence of an enhancing uterus n the pelvis also makes this a little less likely! Whipples, MAI and TB should reasonably be excluded by the amount of abnormality present. Plexiform neurofibroma may cause a very large infiltrating mass with low CT attenuation, but the bone abnormalities would more likely be extrinsic scalloping, the T2 intensity I suspect a little lower and the symmetric pelvic involvement unusual. Nerve sheath tumours may have much the same CT/MR characteristics as a plexiform lesion but if anything be even more likely to be a focal mass.
So none of the usual suspects really fit the abnormality demonstrated. If this were a child and the abnormality in the neck I suspect many would have made the diagnosis of cystic hygroma due to dilated lymphatic structures. This is a related disorder reflecting cystic dilatation of the lymphatic chains explaining the symmetric distribution of very low density, chyle containing spaces that extend down the lymphatic chains.
Please note that this disease entity is distinct from lymphangioleiomyomatosis (=lymphangiomyomatosis) the cystic condition with chylous effusions condition that affects the lungs, although involvement of the lung may also occur in lymphomatosis, predominantly presenting with septal thickening or chylous effusions but not cystic lung change.
Approximately two-thirds of patients with this congenital disease present with symptoms in childhood usually involving the neck, which is the site of involvement in approximately 95% of cases overall. However, adults present more often with diffuse involvement that may involve any organ system including the retroperitoneum, peritoneal cavity, chest, bones and soft tissues. The pancreas and spleen are often involved. Diffuse involvement is increasingly recognised in children too.
The disease is caused by a developmental anomaly in the formation of the lymphatic system with multiple endothelial lined cystic spaces that can be demonstrated on lymphography to communicate with the lymphatic system. The process is benign but may recur locally following excision. Involvement of the bone is similar to involvement elsewhere with cystic chyle filled endothelial lined cells resulting in lucencies that may fill an entire bone. Bone overgrowth and pathological fractures are described. Presentation in children is usually with a mass. In adults presentation may be due to a mass, abdominal pain, ascites or effusions. The mass is often huge at presentation.
Cystic lymphangiomatosis is probably closely related to the conditions cystic angiomatosis and cystic haemangiomatosis where there is a similar cystic proliferation of vascular endothelial spaces, causing very similar soft tissue and bone appearances (but usually with more strands of enhancement). Traumatic biopsy of lymphangiomatosis may result in erroneous diagnosis of cystic angiomatosis due to the presence of blood. Gorham’s disease (massive osteolysis of bone) may represent an aggressive variation of these diseases.
This was an aunt Minnie case: Once seen never forgotten. However all the clues were there to suggest the type of tissues involved (density, location).