Extraneural Metastases in an Operated Case of Pinealoblastoma Identified on Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

Abstract

Extraneural (EN) metastases and leptomeningeal (LM) metastases from certain primary central nervous system (CNS) tumors, such as pinealoblastomas, are not very common and mostly detected on autopsy. Clinical detection of this entity is, however, very rare and can be attributed to increasing overall survival or probably increased use of surveillance imaging in patients with brain tumors. We demonstrate through this case the potential adjunctive role of positron emission tomography/computed tomography in the identification of asymptomatic LM/EN metastases in high-risk primary CNS tumors.

Patient is a 13-year-old female child, a known case of pineoblastoma, who underwent ventriculoperitoneal shunt diversion followed by a surgical decompression and adjuvant radiation to the brain and spine 2 years back. Baseline spinal magnetic resonance imaging (MRI) was negative for disease (images not shown here). The patient was currently asymptomatic, and routine follow-up MRI survey of the brain and spine revealed a T2 hypointense and enhancing intradural lesion in sacral region at S1–S2 level [T2-weighted sagittal, Figure 1a and T1-weighted postcontrast sagittal, Figure 1b, long white arrows]. Rest of the spine and brain was reported as normal. Positron emission tomography/computed tomography (PET/CT) was done for restaging the disease and revealed 2-fluorodeoxyglcose uptake in the intraspinal metastases in the sacral region [sagittal fused PET/CT, Figure 1c, long white arrows]. In addition, PET/CT identified intracranial metastases in the left pontomedullary cistern, which was not reported on initial read of the brain MRI [transaxial PET; Figure 1d, black arrow, transaxial magnetic resonance (MR); Figure 1e and fused PET/MR, obtained using an integrated registration software; Figure 1f, white arrowhead], multiple skeletal metastases [maximum intensity projection; Figure 2a black arrows, and transaxial PET/CT; Figure 2b, white arrow], and peritoneal deposit in the pelvis with associated ascites [sagittal PET/CT; Figure 2c, white arrow].

Figure 1.

T2-weighted sagittal (a) and T1-weighted post-contrast sagittal (b) and Sagittal fused positron emission tomography/computed tomography (c) showing intradural lesion at level of S1-S2 (long white arrows). Transaxial positron emission tomography (d) showing focal uptake in the left ponto-medullary cistern (black arrow) characterized better on trans-axial magnetic resonance, (e) and fused positron emission tomography/magnetic resonance (f) (white arrowhead)

Figure 2.

PET Maximum intensity projection image (a) showing multiple FDG avid skeletal lesions (black arrows), trans-axial positron emission tomography/computed tomography (b) showing a metastatic lesion in the right iliac blade (white arrow). Sagittal positron emission tomography/computed tomography image (c) showing a peritoneal deposit in pelvis with associated ascites (white arrow)

Extraneural (EN) spread from primary central nervous system (CNS) tumors is very rare and seen only in about 0.98% of the patients. In children, primary CNS tumors which have propensity for EN spread includes medulloblastoma, ependymoma, glioblastoma multiforme, pinealoblastoma, and germ cell tumors, with the highest incidence seen in medulloblastomas.[1] The most common sites of metastases include liver, lung, bone, and bone marrow.[2] Studies have also shown an increased incidence of EN metastases in patients with diversion ventriculoperitoneal shunts.[3] Pineoblastomas, a supratentorial primitive neuroectodermal tumor, constitutes 3%–4% of all pediatric brain tumors and considered to have worse clinical outcomes compared to infratentorial primitive neuroectodermal tumors (medulloblastoma).[4] Pineoblastomas have a propensity to spread along cerebrospinal fluid with leptomeningeal (LM) dissemination seen in up to 23% of patients at initial staging and about 44% patients at disease recurrence in one of the case series.[5] EN skeletal metastases from pineoblastomas have also been previously reported.[6] Few case studies have shown the potential clinical utility of PET/CT in diagnosing LM metastases in non-CNS malignancies although its role in identifying LM/EN metastases from primary CNS tumors remains yet to be explored.[7,8] PET/CT imaging in addition to MRI can be of potential clinical utility in planning appropriate treatment in high-risk aggressive CNS tumors (such as medulloblastoma/pineoblastoma), as shown in the case above. Early diagnosis and treatment initiation through such precision imaging, although by no means curative, may nonetheless better the quality of life.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.