Correct!
2. Biopsy of the lower extremity osseous abnormalities
Biopsy of the orbital lesion (Figure 7, arrows) is difficult and unnecessarily invasive when other reliable, less risky methods are available.
Figure 7. Unenhanced (A) and enhanced (B) T1-weighted MRI images of the brain show bilaterally symmetric soft tissue masses (arrows) in the intraconal portions of the orbits. These masses enhance avidly following contrast administration (B).
18FFDG-PET scanning would not provide management-altering information in this patient. If the 18F FDG-PET study shows areas of hypermetabolism, such results would prompt a tissue diagnosis. However, the lack of such hypermetabolism would not allow expectant management without confirmation of the nature of the underlying process. 18FFDG-PET scanning could have a role for directing management, particularly for choosing a site for biopsy, with intervention directed towards tissue showing hypermetabolism and away from abnormalities unassociated with hypermetabolism. However, given the widespread abnormalities in this patient, 18F FDG-PET scanning is probably not needed for such direction. Percutaneous transthoracic needle biopsy of the perivascular material is potentially dangerous- the risk of vascular laceration is significant, and bleeding from such a complication cannot be easily addressed. Biopsy of the bone lesion (Figures 8 and 9, arrows) is a relatively simple procedure with minimal morbidity, and represents a reasonable first step in the attempt to obtain a diagnosis in this patient.
Figure 8. Radiography of the tibia and fibula shows smooth periosteal thickening best seen along the distal tibia (arrows).
Figure 9. Tc-99m Methylene Diphosphonate bone scan shows diffuse, lower extremity radiopharmaceutical uptake, most profoundly affecting the tibias (arrows) but also the distal femurs, consistent with active bone remodeling.
Surgical lung biopsy could provide the histopathological material required for diagnosis in this patient also, but is unnecessarily invasive, given that relatively superficial, accessible, lesions are present, and need not be pursued unless other, less invasive and less morbid diagnostic possibilities have been exhausted.
The patient subsequently underwent percutaneous biopsy of one of the foci of tibial sclerosis. The histopathological material showed inflammatory changes with foamy, lipid-laden eosinophilic histiocytes. Electron microscopy did not show Birbeck granules. Staining for S-100 protein and CD1a was negative, whereas CD68 and factor XIIIa staining was positive.
What is the most likely diagnosis?