Rarity of the Tumor

In the pediatric population, head and neck tumors are rare constituting to only 2 to 5% of all pediatric neoplasms.3 Primary tumors of the jaw are uncommon in pediatric population with the exact incidence estimation being difficult owing to different definitions of pediatric age groups.4 The World Health Organization classified MNTI under “Other jaw tumor type.”3 The first description of the MNTI was by Krompecher in 1918 and its origin was initially unknown.2 Recently, the origin of the tumor is believed to be from the neural crest cells.25 In the last 100 years since the first description of MNTI only around 500 cases have been described from 32 countries.26

It commonly involves the anterior maxilla (62%), skull (15%), mandible (8%), and rarely peripheral bones, testes, and ovaries.26 In our case the location was the anterior maxilla in a female patient. The tumor is usually benign; however, it can grow rapidly with infiltration of bone, soft tissues, etc. Few reports of malignant MNTI have been reported with a metastatic rate of 3%.6

Diagnostic Challenges

On CT scan the tumor's bone destruction will be evident with some components demonstrating hyperdense site due to melanin component. In our scenario, the tumor was hypodense with erosion of floor of the maxillary sinus. On MRI scan the tumor will be usually a well-demarcated hypointense mass on T1-weighted and T2-weighted images.27 In our case it was hypointense. The usual differential diagnosis for anterior maxillary mass in patients will be odontogenic keratocyst, dentigerous cyst, and unicystic ameloblastoma.8

MNTIs were considered the only melanotic odontogenic tumors for quite a long period of time; however, odontomas, odontogenic fibroma, and ameloblastic fibroma are some of the melanin-containing odontogenic neoplasms as described by Bhanu et al.9 The presence of melanin pigment and characteristic biphasic population of cell is characteristic of MNTI. In our case, various radiological differential diagnoses were ruled out based on histomorphology alone.

IHC positivity for HMB45 in epithelioid cells also substantiated the diagnosis of MNTI, whereas uniform negativity for SOX10 ruled out ameloblastomas. Histomorphology and IHC thus serve a vital role in the diagnosis of such rare neoplasms.

Therapeutic Options and Outcomes

The commonly described treatment includes curettage and conservative surgery including resection. There is no difference in recurrence rates between both the modality of treatment according to medical literature.6 Adjuvant treatment modalities like chemotherapy and radiotherapy have been described for recurrent tumors.510 Chemotherapy agents tried are those used for neuroblastomas. They include cyclophosphamide, etoposide, doxorubicin, and vincristine. There are no established protocols for chemotherapy or radiotherapy for such recurrent tumors.211 However, in recurrent cases, surgery is the preferred therapeutic modality.511 Our patient underwent excision under general anesthesia at 7 months' age, and on a 1-year follow-up the patient had no clinical evidence of recurrence. The patient was posted for CT scan but was lost to follow-up. However, the authors opine that a CT scan on follow-up would have carried more benefits than risks to ensure disease-free status and enabled further action if a small lesion is found before it becomes large, complicating the surgical approach. Age at diagnosis has been described as an important prognostic factor for recurrence of disease with age less than 2 months, 2.5 to 4 months, and after 4.5 months having high risk, intermediate risk, and minimal risk, respectively.6 This finding correlated with our case. The recurrence rate described so far in the literature is less than 20% and most of the recurrences occur within the first 6 months of therapy.26

Use of Endoscope

At this point, the authors would like to highlight the use of Hopkin's rigid endoscope 4 mm for cavity inspection to ensure complete tumor removal. Given the small operating field and small patient, the use of an endoscope greatly aids in the surgery. The inaccessible areas like the superior and posterior walls of the maxillary sinus can be best visualized using an endoscope. However, the authors opine that a longer follow-up period with large sample size to evaluate the disease-free status will answer the utility of this modality of management.

Follow-Up

Follow-up of patients is important as the recurrence rate is around 20%.11 Recurrence increases the morbidity and complicates further surgical resection. Some employ the measurement of urinary vanillylmandelic acid (VMA) levels; however, it can be negative even in recurrent cases.10 Some employ the use of repeat imaging like CT scan to identify tumor recurrence.6 The above measures of urinary VMA measurement and repeat imaging may not be possible especially when the patient is from a remote area as in our case. The author recommends that the care givers be counseled about danger signs of recurrence like recurrent swelling, new neurological symptoms, visual disturbance, etc., especially in peripheral center or resource-poor settings.

MNTI as the name implies is predominantly a tumor limited to patients below 1 year of age; however, isolated cases above 1 year are not so uncommon. Kulkarni et al described MNTI in a 2-year-old, Jain et al reports this neoplasm at an unusual age of 10 years, whereas Furtado et al described it in a 13-year-old.12131415 As more and more cases are getting diagnosed, a clear radiological picture of MNTI in the future is a definite possibility.

Clinical and radiological symptoms are not entirely specific; however, urinary VMA levels are usually elevated except in isolated cases where it appears normal. Complete surgical excision provides the best treatment modality with recurrence-free survival.2 Nazira et al reported a case of recurrence of MNTI in a 3-month-old child treated by complete enucleation.16