Atypical Choroid Plexus Papilloma in a Newborn, Misdiagnosed by Ultrasound and MRI: A Case Report

Introduction

Choroid plexus tumors (CPTs) are rare central nervous system neoplasms that can occur not only in children and adults but also in newborns. In children, their incidence rate is less than 10% of all pediatric brain cancers [1], and they usually have a benign presentation [2]. CPTs originate from the choroid plexus epithelium of the cerebral ventricles and can cause hydrocephalus and macrocephaly. According to the histological classification of the World Health Organization (WHO), CPTs can be divided into the following 3 types: choroid plexus papilloma (CPP) is classified as WHO Grade I, indicating it is a low-grade tumor; atypical choroid plexus papilloma (aCPP) is classified as WHO Grade II, indicating it has intermediate features with a higher mitotic rate than CPP; and choroid plexus carcinoma is classified as WHO Grade III, indicating it is a high-grade malignant tumor [3].

Papillomas include CPP and aCPP. The prevalence of CPP is 10–20% of all brain neoplasms in children under 1 year of age [4]. The other papilloma, aCPP, is characterized by aggressive features such as increased mitotic activity and frequent metastases even at diagnosis [5]. It is even rarer and accounts for only 15% [6] of all CPTs. It is difficult to distinguish aCPP from CPP on imaging due to their similar characteristics. In neonates, CPTs may be misdiagnosed at an early stage on cranial ultrasound. The present case aims to help more people recognize the early imaging characteristics of CPTs.

Case Report

A newborn baby girl was admitted to the hospital on the day of her birth with suspected intracranial hemorrhage after visualization of a hyperechoic lesion in the right lateral ventricle by routine ultrasound the day before delivery. The baby girl was born via cesarean section at 40+5 weeks of pregnancy, with a birth weight of 3300 g. Her vital signs and physical examination results were all within the normal range. Her Apgar score was 10 at 1 minute, 5 minutes, and 10 minutes. Her mother had hyperthyroidism during pregnancy.

Cranial ultrasound (Figure 1A–1C) on day 1 showed a lesion in the right lateral ventricle; the right choroid plexus was thicker, with a stronger echo and more Doppler flow than the left side. Due to a lack of experience, a misdiagnosis of intraventricular hemorrhage was made, and clinical observation was recommended. One week later, another ultrasound examination (Figure 1D–1F) showed no significant change of the lesion in the right lateral ventricle. A brain magnetic resonance imaging (MRI) scan was performed at 2 days (Figure 2A–2C) and 2 weeks (Figure 2D–2F) of age. Both showed an isointense mass measuring 1.4 cm anteroposterior, 1.9 cm transverse, and 2.1 cm craniocaudal, which was suspected to be a hemorrhagic lesion located in the right ventricular trigone. The lesion remained unchanged from the 2-day to the 2-week measurement. During hospitalization, the baby girl showed no vomiting, her head circumference was within the normal range, the muscle tone of her limbs was symmetrical, and the rest of the infant’s neurological examinations revealed no abnormalities. Afterwards, she was sent home for continued clinical observation. At 1 month, the infant still had no symptoms or signs during the 1-month check-up. A follow-up ultrasound (Figure 1G–1I), however, showed that the lesion in the right lateral ventricle had enlarged with increased vascularity.

Three months later, the girl underwent a follow-up contrast-enhanced MRI for evaluation of the brain lesion (Figure 2G–2I) due to the progressive enlargement of her head circumference, which had reached approximately 44 cm, and the prominence of the scalp veins. The results showed that the mass had greatly enlarged, with peripheral edema and hydrocephalus. The mass measured 6.2 cm anteroposterior, 6.3 cm transverse, and 7.7 cm craniocaudal. Consequently, the girl underwent surgery to remove the lesion, and the pathological diagnosis was aCPP (Figure 3). After follow-up visits at 6 months, 12 months, and 2 years, the girl showed no signs of residue or recurrence, or metastases, but had persistence of hydrocephalus and subsequent intellectual disability.

Discussion

Brain tumors, such as astrocytomas, medulloblastomas, and ependymomas, are most common in children aged 3–9. Unlike these common brain tumors, CPTs receive relatively little attention in the literature. The choroid plexus produces cerebrospinal fluid, and is the most vascularized tissue in the ventricular system; primary neoplasms of this tissue are highly vascularized and more likely to induce hydrocephalus [2]. CPTs can occur at any age, with 70% of cases reported in patients younger than 2 years old [7]. In the pediatric population, 80% of these tumors are found in the lateral ventricles, 16% in the fourth ventricle, and 4% in the third ventricle [7]. CPTs can present with various clinical symptoms depending on the tumor’s location and size [4]. Symptoms include hydrocephalus, increased head size, and intracranial pressure in infants, and vomiting and headaches in older children.

CPTs are rare tumors without specific clinical patterns or imaging findings in the early stages, and the complex diagnostic landscape increases the probability of delayed diagnosis or misdiagnosis. It is difficult to distinguish aCPP from CPP on imaging. Ultrasound is usually the first-line imaging modality to screen for potential abnormalities in neonates and young infants. On ultrasound, papillomas usually show intraventricular masses with irregular borders and display a heterogeneous and highly echogenic appearance, and have pulsatile intratumoral vascular channels with biphasic flow on color Doppler imaging [4]. Meanwhile, the ventricles are usually dilated. On computed tomography, papillomas are isodense or slightly hyperdense to the gray matter, and are well defined, with a cauliflower-like appearance [8]. The contrast enhancement is intense and slightly heterogeneous, and approximately a quarter of patients exhibit calcification foci within these tumors [2,4]. When lesions are lobulated with irregular margins and exhibit intense, somewhat diverse contrast enhancement, it should raise awareness of choroid plexus carcinoma [4].

On MRI, papillomas are isointense to the white matter on T1-weighted images, and calcifications and intralesional flow voids may be observed [2]. Calcifications are well defined on susceptibility-weighted images. Intense enhancement is visible after intravenous injection of contrast medium [2]. MRI can effectively capture any potential local parenchymal invasion, which can be used to distinguish papillomas from choroid plexus carcinoma [4].

In the present case, the lesion was similar to an intraventricular hemorrhage on ultrasound at the very beginning. However, the gradual enlargement of the hyperechoic lesion, with a large striking appearance, lobular shape, and chaotic and bidirectional flow on color Doppler imaging during several follow-up ultrasound examinations, should have raised our vigilance. On MRI, the lesion appeared as a well-defined, lobulated mass with iso- to hyperintense signals on T1-weighted images and hyperintense signals on T2-weighted images, while the surrounding brain tissue showed relatively uniform signals and showed no mass effect. However, the lesion had a clear boundary that looked like a mass. The lesion did not shrink or disappear like a hemorrhagic lesion upon re-examination, which added to the diagnostic information suggesting a neoplasm rather than a hemorrhagic lesion. We should keep these imaging features in mind and highlight the need for awareness of CPTs.

Conclusions

CPTs are rare tumors that do not have specific clinical patterns or imaging findings. It is uncommon for a neonate to be diagnosed with a CPT, and it can easily be misdiagnosed as intraventricular hemorrhage. When a lesion occurs in the choroid plexus, leading to thickening with a highly echogenic appearance and accompanied by enhanced blood flow signals, brain neoplasms such as CPTs should be considered. Early surgical treatment may improve the prognosis in these cases.