Recurrence patterns in pediatric intracranial ependymal neoplasm: a systematic imaging work-up

Abstract

Purpose: Currently, the different types of ependymal neoplasm (EPN) are defined by anatomical localization and genetics. This retrospective multicenter study aimed to analyze the imaging patterns of both local and distant recurrences in supratentorial (ST) and posterior fossa (PF) EPN.

Methods: We exclusively evaluated patients with recurrent EPN. To form the basis for follow-up evaluations the imaging characteristics for ST-EPN and PF-EPN were assessed and compared to each other. Follow-up assessments included the idenTIFFication of local recurrent tumors, leptomeningeal dissemination, secondary intraparenchymal lesions, and extraneural metastases. MR-signal characteristics of local recurrent tumors were compared to the primary tumor.

Results: The imaging series included 73 patients (median age at diagnosis 4.6 years; 56 PF-EPN). Recurrences were observed at up to five time points, with a total of 145 recurrence events documented. At first recurrence most PF-EPN recurred locally (29/56), while ST-EPN relapsed by intracranial dissemination (9/17). Local recurrent tumor grew fast and differed in up to one-fifth from the primary (13.2% lower T2-signal, 14.6% brighter T1-signal, 19% less contrast-enhancement). Leptomeningeal dissemination in ST-EPN is mainly restricted to intracranial (90.5%) while PF-EPN more frequently present with spinal spread (45.7%). Transient post-radiogenic lesions (n = 2) and secondary malignancies (n = 2) were rare. Extraneural metastases (n = 3) were found mainly near the surgical access.

Conclusion: Recurrences can occur multiple times in EPN patients, and the recurrence patterns differ between ST-EPN and PF-EPN. Imaging characteristics of local recurrences can differ from the primary tumor which is crucial for accurate diagnosis and treatment planning.

Keywords: Child; Ependymoma; Magnetic resonance imaging; Neoplasm metastasis; Recurrence.

Fig. 1

A 2-year-old girl with a posterior fossa ependymoma (A-D) and a 2-year-old boy with a supratentorial ependymoma (E-H), both at diagnosis. (A-D) The upper row shows the typical appearance of a posterior fossa ependymoma. (A) The signal on T2-weighted images is brighter than the cortex. (B) Only a portion of the tumor shows moderate contrast-enhancement. (C) On B1000 DWI image, the tumor shows intermediate signal without unequivocal restriction since the signal on ADC map (D) is predominately brighter than the cortex. (E-H) The lower row presents a ZFTA-fusion positive supratentorial ependymoma. (E) The large tumor mass with massive edema and moderate contrast-enhancement (F) in the left hemisphere led to subfalcine herniation (white arrow in E) and hydrocephalus. Restriction on diffusion-weighted images (B1000 image in G and corresponding ADC map in H) and intermediate signal intensity on T2-weighted images (E) illustrate high cell density on MRI, which is noticeably in contrast to the posterior fossa ependymoma

Fig. 2

A 1-year-old girl with a posterior fossa ependymoma. (A-C) At diagnosis. The primary tumor showed strong contrast-enhancement (A) and inhomogeneous hyperintense signal intensity on T2-weighted and FLAIR images (B, C). (D-F) Local recurrent tumor at time-point 1, two years after total resection. The new lesion is best seen on T2-FLAIR (E) and T2 (F). T2-signal was similar compared to the primary tumor but there was lack of contrast-enhancement (D). (G-I) Local recurrent tumor at time-point 2, 22 months after time-point 1. The recurrent tumor now shows signal intensities resembling the primary tumor

Fig. 3

A 9-year-old boy with a ZFTA-fusion positive supratentorial ependymoma in the right frontal lobe at diagnosis on T2-weighted (A) and post-contrast T1-weighted images (B). The patient had at first relapse a local recurrent tumor 43 months after initial total resection. On follow-up two further local recurrences occurred. The local recurrent tumors never crossed the midline. (C-E) The fourth recurrence was a left sided leptomeningeal metastasis with very similar signal intensities on T2-weighted (D) and post-contrast T1-weighted images (C, E). The tumor tissue contained a large central non-solid area (*) at diagnosis (A) and in relapse (D). (E) shows the broad-based contact of the metastasis to the dura mater. (F) The patient simultaneously showed a second leptomeningeal metastasis at the right frontal base

Fig. 4

Extraneural metastases on follow-up (T2-weighted images). (A) A male patient diagnosed with a supratentorial ependymoma at the age of 10 developed a new subcutaneous soft tissue lesion near the first surgical access more than four years after the first resection. (B) A female patient diagnosed with a supratentorial ependymoma at the age of 11 developed a new subcutaneous lesion without connection to the surgical access more than four years after diagnosis. Here, no lymph nodes were present on earlier MRI studies. (C) A male patient diagnosed with a posterior fossa ependymoma at the age of 4 developed a large extracranial mass along the way of surgical access six years later

Fig. 5

Examples of secondary lesions. (A-C) A 12-year-old boy diagnosed with a posterior fossa ependymoma developed a diffuse pontine lesion 23 months after diagnosis and a diffuse intrinsic pontine glioma was suspected. (A) Tumor manifestation started with a slight and diffuse increase in T2-signal intensity within the central pons. (B) MRI 10 months later shows the growth of the pontine T2-lesion, now fulfilling the criteria for a diffuse pontine glioma. (C) On further follow-up, the tumor is expanding into the cerebellar hemisphere. (D-F) A 2-year-old boy diagnosed with a supratentorial ependymoma (MRI at diagnosis in Fig. 1). (D) The first MRI control six weeks after proton therapy shows the left sided postoperative parenchymal defect without tumor residues but bilateral subdural hygroma on T1-weighted post-contrast images. (E) Six months after radiotherapy, new contrast-enhancing spots occur nearby the resection cavity, but also within primarily healthy brain tissue in the area of the right-sided central region. (F) Follow-up three months later shows regression of the contrast-enhancing spots, which supported the assumption of transient post-radiogenic imaging changes