AJNR Case Collection

Posttransplant lymphoproliferative disorder (PTLD) remains a significant concern in solid-organ transplant recipients, accounting for 21% of all transplant-related cancers. Risk factors for PTLD include the type of transplanted organ, EBV mismatch at time of transplantation, and the intensity and duration of immunosuppressive therapy, with increased risk associated with tacrolimus, taken by the patient in this case. The imaging appearance of PTLD is variable, and in most cases, there are multiple masses with peripheral enhancement, central necrosis, and vasogenic edema. However, PTLD can present as solitary masses like in this case. The lesion also had a peripheral pattern of punctate intratumoral susceptibility signal (ITSS), which was reported in previous cases. The PTLD disease spectrum ranges from lymphoid hyperplasia to malignant lymphoma and the treatment regimen varies significantly. A surgical biopsy was performed and diffuse large B-cell lymphoma was diagnosed on pathology in this case.

Neurotoxoplasmosis was considered due to the patient's immunocompromised status and new neurologic symptoms. While ring enhancement and variable degrees of diffusion restriction are imaging findings consistent with toxoplasmosis, it more commonly presents as multiple lesions and the usual locations are the basal ganglia and corticomedullary junctions.

Brain metastases typically occur at gray-white matter junctions and arterial watershed areas. The imaging appearance is variable and can present with ring enhancement, intermediate diffusion restriction, and peripheral and adjacent fissural hemorrhage, depending on the primary tumor.  Although these are mostly multiple lesions, single metastasis is not uncommonly seen as metastases overall are the most common type of intracranial tumors. The patient underwent CT chest/abdomen/pelvis for cancer work-up, and it was negative.

Subacute intracranial hematoma was suspected given the faint hyperdensity observed on CT as well as mild T1 intrinsic hyperintensity and ring enhancement on MRI. Peripheral only, not peripheral and central, SWI hypointensity can be seen in the late subacute stage; however, the extensive vasogenic edema is not typical for the subacute stage. Moreover, the clinical course in this case suggested an acute process.

Teaching Points:

• In transplant patients, the presence of ring-enhancing lesions with intermediate diffusion restriction and a peripheral pattern of ITSS should raise suspicion for PTLD.
• Accurate identification of the imaging features can greatly expedite the management as surgical biopsy is often required to guide the treatment, which can vary significantly across the disease spectrum.