Melanotic neuroectodermal tumour of infancy: A case report and differential diagnosis

Abstract

Melanotic neuroectodermal tumour of infancy is an uncommon pigmented neoplasm of neural crest origin. It was first described in 1918 by Krompecher, known as congenital melanocarcinoma at that time. Although it is generally agreed upon that it is a benign entity, it is locally aggressive and has a significant recurrent risk, reported to be between 10-15%. There have also been prior reports of malignant behaviour in these tumours, although extremely rare. The majority of cases of this tumour (about 70%) arise from the maxilla and its occurrence in the cranial vault represents approximately 15.6% of cases. We describe a rare case of melanotic neuroectodermal tumour of infancy, with simultaneous involvement of the cranial vault and petrous temporal bone, in a four-month-old child, complicated by post-surgical pseudo-meningocele. This case illustrates the diagnostic dilemma in differentiating reactive osseous sclerosis from direct tumour infiltration, both of which can occur in the context of melanotic neuroectodermal tumour of infancy. The discussion places emphasis on differential diagnoses and useful radiological features to assist in clinching the diagnosis of melanotic neuroectodermal tumour of infancy.

Keywords: Melanotic neuroectodermal tumour of infancy; cranial vault mass; pigmented neoplasm; pseudo-meningocele.

Figure 1.

Lateral (a) and frontal (b) skull radiographs showed a sclerotic lesion in the left parieto-occipito-temporal cranial vault. Computed tomography (CT) demonstrated a solitary osseous-based lesion with marked spiculated periosteal reaction (c) and mildly hyperdense soft tissue component abutting the inner and outer tables of the left cranial vault (d).

Figure 2.

On magnetic resonance imaging (MRI), the soft tissue component showed (a) mildly hypointense signal on T2-weighted images and (b) hyperintense signal on T1-weighted images. Mass effect upon the underlying left temporo-parietal lobes was observed with mild vasogenic oedema within the left temporal lobe.

Figure 3.

The histology showed a tumour composed of three elements; small neuroblastic cells (a), a dense fibrous stroma ((a) and (b)) and islands of epithelial cells containing pigment (b). Scale bars – 100 µm.

Figure 4.

A large calvarial defect was present after the surgery due to the large size of the lesion, (a) and (b). A few weeks after surgery, a large fluctuant mass was seen at the surgical site, confirmed to be a pseudomeningocele on magnetic resonance imaging (MRI). The pseudomeningocele continued to grow in size over a duration of six months despite compression bandaging, (c)–(e).

Figure 5.

Coronal T2-weighted images (a) before surgery, (b) one month after surgery and (c) one year after surgery demonstrated an area of residual sclerosis within the left petrous temporal bone which subsequently showed interval reduction in extent on follow-up at one year. Coronal computed tomography (CT) image (d) showed the area of residual sclerosis within the left petrous temporal bone one month after surgery.