A case report of pontine glioblastoma presenting as subcutaneous metastasis in nape of neck in a child.

Glioblastoma (GBM) is the most common malignant tumor in adults. Extracranial metastasis of GBM is very rare. The incidence of brainstem glioblastoma is not known due to low biopsy and resection rates. In this case report, we experienced an 11-year-old male who was diagnosed as a case of pontine GBM after biopsy of lesion and underwent radiotherapy with adjuvant chemotherapy. He presented with a subcutaneous swelling in the nape of neck 1 year after the first procedure. Swelling was excised. Pathological examination and immunohistochemical staining confirmed it as GBM. This case shows us that GBM can at times present as a swelling in soft tissue.

Introduction

Extracranial metastasis of glioblastoma (GBM) is very rare. Metastasis is present in <2% of cases.[1] The exact incidence of brainstem GBM is not known due to low biopsy and resection rates. All the cases of subcutaneous metastasis of GBM reported until now have followed either craniotomy or biopsy.[23] GBM metastases outside the central nervous system (CNS) is very rare, so these tumor's management experience is very less. Here, we present a patient with pontine GBM, who presented with a swelling in the nape of neck following surgery, radiotherapy, and chemotherapy.

Case Report

An 11-year-old male presented with the complaints of weakness of the left upper and lower limb with progressive difficulty in swallowing. Magnetic resonance imaging (MRI) of lesion was done which showed a ring-enhancing lesion in the pons on gadolinium contrast with perilesional edema [Figure 1a and b].

Figure 1

(a) First preoperative sagittal T1-weighted image showing an isointense lesion in pons with surrounding hypointensity in the midbrain and pons. (b) Sagittal T1-weighted image contrast showing ring enhancement. (c) Second preoperative sagittal T2-weighted image showing a hyperintense lesion in the pons with subcutaneous iso to hyperintense lesion in the subcutaneous region of the nape of the neck. (d) Sagittal T1-weighted image contrasts showing ring enhancement of the pontine lesion and contrast enhancement of subcutaneous lesion

The patient underwent midline suboccipital craniectomy and tumor decompression. In the postoperative period, the patient underwent elective tracheostomy as he had lower cranial nerve palsy. He was later weaned off the ventilator. One month after the operative intervention, the patient was discharged after closure of the tracheostomy. Pathological examination of the lesion showed high-grade malignant tumor with predominant astrocytic differentiation. Mitosis and necrosis were also evident. Overall morphology was consistent with GBM, WHO grade IV as seen on hematoxylin and eosin stain. Immunohistochemical results showed tumor cells positive for glial fibrillary acidic protein with MIB index more than 15–20. The tumor cells showed epithelial membrane antigen negativity [Figure 2a–c].

Figure 2

Pathological and immunohistochemical examination of the primary tumor after operative interventions. (a) A low-power view of the tumor showing necrosis (H and E, ×20); (b and c) immunohistochemical results showing MIB index more than 15 and tumor cells positive for glial fibrillary acidic protein (×20); (d) intramuscular invasion by tumor cells (H and E, ×20); (e) tumor cell necrosis and subcutaneous fat nodules (H and E ×20); (f) immunohistochemical results showing tumor cells positive for glial fibrillary acidic protein (×20)

Postoperatively, the patient underwent radiotherapy (60 Gy in 30 cycles). Adjuvant chemotherapy with temozolomide 75 mg/m2 was given for 5 cycles, but the patient's parents stopped giving the drugs due to side effects such as nausea, vomiting, and headache. One year after the operative intervention, the patient's parents noticed a swelling on the nape of the neck, gradually increasing in size for 2 months. There was reddish discoloration over the swelling since past 20 days [Figure 3a–c].

Figure 3

(a-c) Preoperative pictures before the second operative intervention showing a subcutaneous swelling in the nape of neck with reddish discoloration with healthy previous operative scar mark

No discharge was present from the swelling with no history of fever or restriction of neck movements. On inspection, a single swelling of 4 cm × 5 cm with smooth surface with reddish discoloration was present in the nape of the neck. Healthy scar of previous surgery was present over the swelling. On palpation, local temperature was raised, mildly tender; firm and edges were well-defined and regular. The skin over the swelling was pinchable. Follow-up MRI with gadolinium contrast showed a subcutaneous swelling in the nape of the neck with contrast enhancement [Figure 1c and d].

The swelling was resected, and postoperatively, the patient underwent elective tracheostomy due to subglottic stenosis. Pathological examination showed the characteristics of GBM [Figure 2d and f].

The patient was weaned off the ventilator and then discharged with tracheostomy in situ. The patient underwent radiotherapy (60 Gy in 30 cycles) with adjuvant temozolomide chemotherapy (75 mg/m2) for 5 cycles. The patient is in follow-up until now and is without recurrence at the subcutaneous site.

Discussion

GBM is the most common malignant brain tumor in adults, but it has less common occurrence in pediatric age group. GBM can metastasize to a wide variety of locations depending on the type of mechanism for metastasis. Extracranial GBM metastases occur in only about 0.4–2.0% of patients although they account for approximately two-third of the neuroepithelial tumors that metastasize extracranially.[45] The site of GBM metastases occurs most often in the lungs and pleura (60%), regional lymph nodes (51%), bone (31%), and liver (22%).[67] GBM with subcutaneous metastasis is extremely rare and can be misdiagnosed. Brainstem gliomas have an incidence of 1.4% of intracranial tumors in pediatric age group and comprise 28.7% of posterior fossa tumors in pediatric age group.[8910] The exact incidence of brainstem GBM is not known due to low biopsy and resection rates of these lesions.

Only 11 cases of intracranial GBM with subcutaneous metastasis have been reported until now, of which 1 case is of pediatric age group and 1 adult case of pontine GBM.[23] This is the first pediatric case of pontine GBM with subcutaneous metastasis and 12th case overall to be reported.[23] GBM metastasis to extracranial sites is rare because of patients with GBM do not survive long enough due to aggressive nature of the disease. Metastasis from GBM are rare because of the following reasons – cerebrum does not have a true lymphatic system, intracranial venous sinuses are enclosed in a dense dural membrane making it difficult for tumor cell penetration, intracerebral veins are thin walled and might collapse from compression before being penetrated by an expanding tumor mass, the extracellular matrix and tough basement membrane surrounding intracerebral blood vessels, the lack of communicating channels between the intracerebral perivascular space and extracerebral fluid space, intermittent nature of communications between subarachnoid space and extracerebral lymphatic vessels, and finally immunological response of host organ to neuroglial tumor cells may prevent their growth outside the CNS. Occurrence of extracranial GBM metastasis is usually associated with previous craniotomy, biopsy, or ventriculoperitoneal shunting. Craniotomy and biopsy breach the defense mechanisms enabling tumor cells to gain entry to the lymphatic system, meningeal, and vertebral venous system at the dural or intracerebral level.

In the present case, GBM could have spread through local dissemination or hematogenous spread since the swelling was located just below the line of previous incision, and pathological examination showed a medium-sized blood vessel with tumor emboli with attempts of recanalization. Subcutaneous GBM metastasis is very rare; it is suggested that the previous history with pathology and immunohistochemistry should be known. At follow-up till now the patient is free from any recurrence at the local site.

Conclusion

GBM with extracranial subcutaneous metastasis is extremely rare. As the patient survival has increased these days, such atypical presentation is likely to increase. To reduce the incidence of these metastases, one should change the surgical instruments and gloves after dura closure. Knowledge of underlying diagnosis of prior intracranial GBM along with pathological and immunohistochemical examination are the two mandatory tools required for the diagnosis of subcutaneous swelling. The best treatment advised for these tumors would be excision of mass followed with radiotherapy and chemotherapy.

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Conflicts of interest

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