The skull radiograph (Fig 1) showed calcification in the region of the pineal gland. The radiograph of the left hand (Fig 2) was performed to assess the bone age. According to the bone age estimation standards of Greulich and Pyle, the bone age was 11 years 6 months, which was more than 2 standard deviations above the mean for the chronological age of the patient.

As the skull radiograph findings were suspicious of a pineal gland tumour, a magnetic resonance (MR) scan of the brain was performed (Figs 3A - C). This showed a 2.0 x 1.5 x 1.8 cm pineal tumour with mixed signal intensities on both T1-weighted (T1-W) and T2-W pulse sequences. There was fairly marked enhancement after intravenous gadopentetate dimeglumine (Gd-DTPA) was administered.

DIAGNOSIS

Germinoma of the pineal gland.

CLINICAL COURSE

Beta-human chorionic gonadotrophin (beta-HCG) was raised at 16.3 IU/L. Alpha feto-protein (AFP) and carcinoembryonic antigen (CEA) levels were normal. The patient underwent subtotal excision of the tumour. Histopathological diagnosis confirmed the diagnosis of a germinoma. Post-operatively, the patient was given chemotherapy and is currently doing well.

DISCUSSION

Intra-cranial calcification in the pineal region is extremely rare in children less than 10 years of age(1). A pineal tumour should be suspected especially if the lesion is greater than 1 cm in size. Pineal region tumours are generally divided into tumours of germ cell origin, pineal cell origin and pineal cysts. Metastases and para-pineal lesions such as gliomas occur much less frequently. Germ cell tumours are the commonest tumours of the pineal region(2). Of the different types of germ cell tumours in this area, germinomas are the commonest, accounting for 65% of cases. Non-germinomatous germ cell tumours such as teratomas, endodermal sinus tumours and choriocarcinomas account for 26% of cases. Nine percent have a mixed histology(3). There is a 10:1 male predominance with a peak incidence occurring in the second decade.

Imaging findings of pineal region tumours often overlap, but may sometimes have unique features. Germinomas are characteristically hyperdense on CT with calcification often noted in the region of the pineal gland. It is believed that the tumour itself does not calcify but calcification is often seen within the pineal gland itself(6). On MR imaging, the tumour has intermediate signal intensity on T1-W sequences and enhances markedly. It is characteristically slightly hypointense on T2-W sequences. Teratomas are believed to arise from all three germ cell layers of the developing embryo, ie. ectoderm, mesoderm and endoderm. Mature teratomas may sometimes show characteristic findings on CT and MR imaging due to the presence of fat, bone, calcification and cystic components. On CT, the appearance of the lesion varies according to the components present. High density irregular calcifications and low density fat may be seen (Fig 4A). These tumours show heterogeneous signal intensities on all MR sequences(7) (Figs 4B, C). They enhance irregularly due to the presence of non-enhancing lipid and bone components.

Pineal cysts are seen in up to 5% of MRI studies(4). They are usually small (less than 1.5 cm in size), asymptomatic, incidental findings on MR imaging (Figs 6A - C), although they may occasionally compress the aqueduct causing hydrocephalus(6). They may however have a variable MR appearance depending on their contents(7). They may be confused with neoplastic lesions because some cysts may enhance on delayed images after the administration of intravenous contrast. This is due to the diffusion of contrast from the surrounding pineal gland tissue into the cyst(7). It is therefore important to image these lesions immediately after the administration of intravenous contrast before contrast diffusion into the cyst occurs(4).

Gliomas may occur in the pineal gland region and they most often arise from adjacent structures rather than from the astrocytes within the pineal gland itself(8). Most tumours in this region are pilocytic astrocytomas(9). They are usually hypodense on CT, and are of low signal intensity on T1-W and of high signal intensity on T2-W MR images(2). When the tumour is large, the site of origin may be uncertain and differentiation from true pineal gland lesions becomes impossible. Metastatic lesions to the pineal gland are rare, occurring in only 1.8% to 4.0% of autopsy cases in patients dying of malignant neoplastic disease(7). Metastases to the pineal gland do not normally occur in isolation. They occur most commonly in patients suffering from carcinomas of the lung and breast. The imaging findings are non-specific.

In summary, the imaging findings of pineal gland tumours are often non-specific although occasionally characteristic findings may occur. Correlation with the germ cell tumour markers may be helpful in differentiating the different types of germ cell tumour but the final diagnosis is often possible only after a tissue specimen has been obtained.

ACKNOWLEDGEMENT

We thank Dr P W Cheng of the Department of Diagnostic Radiology, Queen Mary Hospital, Hong Kong for providing Figs 6A - C.

Tumours occurring in the region of the pineal gland are uncommon in paediatric patients but may manifest with typical signs and symptoms. A 6-year-old boy with precocious puberty caused by a germinoma of the pineal gland detected on skull radiographs and confirmed on MR imaging is reported. The different types of tumours occurring in the region of the pineal gland and their imaging findings are discussed.

Department of Diagnostic Imaging
KK Women’s and Children’s Hospital
100 Bukit Timah Road
Singapore 229899

H E L Teo, MBBS, FRCR
Senior Registrar

Department of Paediatrics
KK Women’s and Children’sHospital

A M Tan, MBBS, MMed (Paed), FAMS
Senior Consultant and Head

Correspondence to: