Clinical and imaging features of melanotic neuro-ectodermal tumor of infancy of the maxillary bone: report of four cases and review of the literature

The study was approved by the institutional review board. We retrospectively reviewed the imaging findings of four patients with histology-proven MNTIs over a 5 year period (July 2016–June 2021) by searching the clinical records. All four patients underwent surgical treatment. The clinical presentations, surgical findings and histological diagnosis were extracted from the medical records.

The four patients all presented to the department of oral and maxillofacial surgery and underwent CT examination. Images were acquired in both the axial and coronal planes using Revolution CT, GE Healthcare. The imaging parameters were as follows: voltage 100 kV, current 200 mA, matrix 512 × 512, section thickness 0.625 mm. Examinations were performed from superciliary arch to the submandibular region. Images were reconstructed using both bone algorithm (window width 2000 HU at a window level of 600 HU) and soft-tissue algorithm (window with 350HU, window level 40HU). Case 1 and case 2 got enhanced CT check in which 2 ml of iodixanol injection (Visipaque, GE Healthcare Ireland Limited) per kilogram of body weight was applied via intravenous injection.

Case 3 and case 4 also underwent MR examination prior to surgery. All MRI was acquired on a 3-T scanner (Achieva, Philips Medical System, Best, the Netherlands), using a head coil. They underwent pre-enhanced T1- and T2-weighted scanning and case 3 also had post-enhanced T1-weighted images in the axial, coronal and sagittal planes. The imaging parameters were as follows: T1-weighted images: repetition time (TR) 500–600 ms, echo time (TE) 15–20 ms; T2-weighted images: TR 4000 ms, TE 80–100 ms, matrix 512 × 512, field of view 20 × 20 cm, and section thickness 2.5 mm. Rapid manual bolus intravenous injection (2 ml s⁻¹) of 0.1 mmol of gadopentetate dimeglumine (MagnevistH; Schering AG, Berlin, Germany) per kilogram of body weight was administered.

In addition, cervical and abdominal ultrasonic inspections were also performed for screening metastasis features of lymph nodes or abdominal organs.

All the images were evaluated by three experienced oral and maxillofacial surgeons/radiologists and findings were reached by consensus.

Biopsy operations were scheduled for the four patients before resection operations. The final pathological diagnosis of MNTI by surgery was consistent with biopsy.

Case 1

A 6 month-old male presented with a 3 month history of painless swelling of the right maxillary region. Clinical examination showed a non-tender, non-ulcerated, blackish-grayish tumor causing craniofacial asymmetry. CT demonstrated a multi-locular soft-tissue mass occupying the right maxillary sinus and leading to irregular bony destruction. Cortex expanded and lost continuity without periosteal or bony proliferation. Several displaced tooth germs were noticed in the tumor. Contrast-enhanced CT showed heterogeneous enhancement of the lesion (Fig. 1). Diagnosis of MNTI was made by biopsy. The cervical and abdominal ultrasonic inspections showed no metastasis features of lymph nodes or abdominal organs. The patient was given surgery by enucleation under general anesthesia, and monitored every 6 months for 3.5 years, without evidence of recurrence.

Fig. 1

Case 1. a/b axial CT images demonstrated a multi-locular soft-tissue mass occupying the right maxillary sinus and leading to irregular bony destruction. Cortex expanded and lost continuity without periosteal or bony proliferation. Displaced tooth germ was noticed. c coronal contrast-enhanced CT showed heterogeneous enhancement of the lesion

Case 2

A 1-month-old female was admitted owing to a rapidly growing tumor of left maxilla of 2 weeks’ duration. The patient had left nasal obstruction, proptosis, and facial malformation. Clinical examination revealed a large and firm mass from midline to left maxillary tuberosity. Mucosa surface of the tumor was intact with blueish-grayish color. CT revealed osteolytic and expansive bone destruction of left maxilla, involving all maxillary sinus walls and inferior orbital wall. Spiculated/sunburst periosteal reaction was obvious. Irregular and ill-defined soft-tissue mass in which tooth germs floated was noticed in the bone destruction area. Contrast-enhanced CT scans showed medium heterogeneous enhancement of the soft-tissue mass combining with liquefactive necrosis areas (Fig. 2). Diagnosis of MNTI was made by biopsy. No metastasis features of lymph nodes or abdominal organs were demonstrated by cervical and abdominal ultrasonic inspections. The patient also had eye examinations and fibro nasopharyngoscopy due to nasal obstruction and proptosis. Curettage was taken to treat the patient under general anesthesia, while 1 month later, a recurrent lesion was found in the left maxilla. Thus, a second enucleation surgery with subtotal resection of maxilla was undertaken. Regular follow-up examination 31 months after the second surgery revealed no evidence of recurrence.

Case 3

A 7 month-old male was referred with progressive right facial swelling for 3 months. The patient suffered from right nasal obstruction, feeding difficulty, ocular proptosis and facial deformity. Clinical examination showed giant (about 10 cm * 8 cm) and non-ulcerated invading right orbit, nasal cavity and whole right maxilla. Mucosal of the tumor was intact with grayish–whitish or grayish–blackish color. CT showed tissular expansive tumor with obscure boundary, leading to extensive bone destruction, local spiculated periosteal reaction and fragmentary cortical bone. Right maxilla, infratemporal fossa, pterygopalatine fossa, orbital apex and cavernous sinus were involved. Several displaced/ “free-floating” teeth were distinct. Right orbit was smaller than the contralateral side causing by the compression of neoplasm. Nasal septum was also compressed tipping to left side. On MRI, the tumor appeared isointense or lightly hypo-intense on T1-weighted sequences, lightly hyper-intense on T2-weighted sequences, and show intense but inhomogeneous enhancement following gadolinium injection. Involvement of right orbit, orbit apex area, cavernous sinus and right optic nerve was more clear on MRI than CT (Fig. 3). The cervical and abdominal ultrasonic examinations seemed quite necessary for this child, while no metastatic lymph nodes or abdominal organs were found. The lesion was excised by enucleation with subtotal resection of maxilla under general anesthesia. Clinical and imaging follow-up every 6 months for 26 months showed no evidence of recurrence.

Case 4

A 5 month-old male was referred because of a rapidly growing tumor of the maxilla. The first symptoms of swelling in the right maxilla region had been noticed about 2 months before. Clinical examination revealed a firm, lobed, non-ulcerated, reddish-bluish tumor with intact mucosa. CT scans showed irregular bone destruction and cortical bone expansion, with no signs of periosteal reaction. Teeth in the lesion were displaced. On MRI, the mass was isointense or mild hyper-intense on both T1- and T2-weighted sequences with clear boundary (Fig. 4). Surgical enucleation of the tumor mass was planned under general anesthesia. During the 12 month follow-up period, there was no evidence of recurrence of the mass.