Presentation
Pitting edema in both legs.
Patient Data
Huge bilateral solid perirenal masses with hypodense radial striations, insinuating into the renal sinuses and distorting the kidneys. The right mass measures 11.3 x 14.4 x 24.0 cm and the left measures 13.8 x 21.8 x 30.2 cm. There is severe thinning of the renal parenchyma of both kidneys in several places. In the excretory phase (~4 min after the nephrographic phase), contrast material only fills the renal collecting system bilaterally but does not extend into the ureters, possibly due to early timing.
Periaortic soft tissue partially enveloping the thoracic aorta. Rest of thorax (additional study, not shown) normal.
Small hepatic nodule in segment 6, only visible and hypoenhancing in the nephrographic phase - perhaps a hemangioma. Tiny non-enhancing hypodense focus in segment 3 abutting the left hepatic vein - probably a cyst.
Small sliding hiatal hernia.
Tiny adenoma in lateral arm of right adrenal gland, several small adenomas and tiny myelolipoma in left adrenal.
Small hemangioma in the L2 vertebral body.
Huge solid perirenal masses enveloping the kidneys, causing a deformation of the renal contours as well as their displacement and malrotation, and infiltrating the renal sinuses and around the proximal ureters. The masses are hypointense on T2WI and hypointense on T1WI, with mild progressive enhancement only. There are radiating bands/septations in the masses, most likely due to internal fibrotic changes. Small simple cortical renal cysts in both kidneys. Symmetric renal excretion. No hydronephrosis except for mildly dilated superior calyx in the right kidney. The renal arteries convoluted due to the kidneys' position, the renal veins are flattened at the renal hila.
Two hepatic lesions undergo arterial enhancement, one in segment 2 measuring 12 mm across, the other in segment 4a measuring 26 mm across. Another focal lesion segment 5 measures 11 mm across and has the characteristics of a hemangioma. Simple cyst 6 mm across in segment 3.
Nodules displaying signal drop in both adrenal glands - adenomas. Tiny fatty focus in the left adrenal - myelolipoma.
Circular perivascular thickening around the inferior part of the descending thoracic aorta (partly included in some of the sequences). Short segment of perivascular thickening in the distal abdominal aorta that displays an abnormal signal in the DWI sequence.
Degenerative changes along the thoracolumbar spine. Hemangioma in vertebral body of L2.
Small amount of free fluid seen in the pelvis which is only partly included in some sequences.
In summary:
Huge perirenal masses involving the renal sinuses and enveloping the proximal ureters. Periaortic soft tissue in the thoracic and abdominal aorta. The imaging findings are in keeping with Erdheim-Chester disease, with renal, perirenal and vascular involvement.
Moderately increased FDG-glucose uptake in the perirenal and periaortic masses.
Moderately increased FDG-glucose uptake in the perirenal and periaortic masses.
There is a clear regression in the size of both perirenal masses.
Case Discussion
Arrived at the ER due to bilateral lower limb edema.
All vital signs were normal. CRP 56.
Doppler ultrasonography of the lower limb veins, both deep and superficial, and arteries was essentially normal.
CT abdomen was performed to investigate for a pelvic mass, which showed huge bilateral renal masses and periaortic soft tissue. The putative diagnosis was of Erdheim-Chester disease, the differential diagnosis for the perirenal masses consisting of perirenal fibromatosis, lymphoma, IgG4-related disease, and desmoid tumor.
An ultrasound-guided biopsy was obtained from one of the perirenal masses.
Interestingly, there was virtually no radiologic sign of bone involvement, though when asked by the radiologist whether he had been suffering from bone pain, he nodded vehemently.
Pathology:
Perirenal mass, biopsy:
Histiocytic lesion (SEE COMMENT).
COMMENT:
The specimen consists of fibrous tissue in which cells with abundant foamy cytoplasm are seen. Giant cells are not seen. The cells are positive for CD68 and vimentin and are negative for CD1a, CD34, CD117, DOG1, MUC4, EMA, MDM2, S-100, SOX 10, desmin, beta-catenin, actin, caldesmon, IgG4, Langerin and BRAF. The morphology and immunohystochemical results are those of a histiocytic process and essentially rule out fibromatosis, lymphoma, IgG4 disease, desmoid tumor and liposarcoma. "The diagnosis of Erdheim-Chester disease is based on clinical features, imaging and histology" (WHO fascicle). In the appropriate clinical setting, these findings would be consistent with a diagnosis of Erdheim-Chester disease.
A renal MRI was performed, which, in addition to the CT, showed two small arterially-enhancing hepatic foci and showed the circular thickening at the distalmost aorta to be in fact periaortic soft tissue, not soft atheromatous plaque.
A brain-orbits MRI and a cardiac MRI were performed (not shown), both of which were normal.
An additional biopsy specimen was sent to a world-renowned lab for both pathological and molecular studies, which corroborated the diagnosis of Erdheim-Chester disease and found the C121S mutation in the MAP2K1 gene.
Same-day baseline PET-CT and PET-MRI were done before initiating treatment with the MEK inhibitor cobimetinib.
3 months after starting treatment, a follow-up PET-CT (not shown) revealed a modest size regression and decreased radiotracer uptake in the perirenal and periaortic masses.
Several weeks later, renal ultrasonography revealed yet further size regression of the perirenal masses.