Approximately 200 cases of MNTI have been reported in the literature. An exact number is difficult to discern because of the variety of terms that have been applied to the lesion in the past.16
Krompecher in 1918 first described the tumour as congenital melanocarcinoma.1
Mummery and Pitts in 1926 named the tumour as melanotic epithelial odontome and suggested it to be of odontogenic origin.7
The tumour was then called as melanotic prognoma by Stowens in 1957, who proposed a phylogenetic theory concerned with displaced neuroectodermal tissue from vestigial organ of Jacobson,3
and pigmented congenital epulis by Henry and Bodian in 1960.5
It was Misugi et al8
in 1956 who first proposed neural tissue to be the source of MNTI, this was later supported by Borello and Gorlin in 1966.9
Clinically, MNTI is a fast growing, non-ulcerated swelling in the incisal region of the maxilla. The most common site of occurrence was anterior maxilla as proposed by Dahlback and Thilander in 1964.16
It has been reported at other sites also including skull, mandible and brain.2
However the occurrence of tumour in other anatomical locations such as skin, epididymis, uterus, ovary and mediastinum was independently described by Ashley et al17
in 1964 and Dehner et al18
in 1986. Pontius et al19
in 1965 reported a case with occurrence of multiple lesions although MNTI generally occurs as solitary lesions. Pigmentation on the overlying soft tissue may be observed in only some cases.
Shafer et al
in 1983 commented that MNTI occurs predominantly in children, with about 92% of patients presenting with the tumour in the first year of life, and about 82% usually in the age range of 1–6 months. The mean age of presentation was 4.3 months.2
Hupp et al
in 1981, in a review of 139 positively confirmed cases of MNTI showed 43% of them occurring within the first 3 months of age.20
Isolated cases of occurrence of MNTI in older adults are also reported.21
An equal gender predilection was proposed by Mosby et al22
High levels of urinary VMA elaborated by the tumour was first reported by Borello and Gorlin in 1966 suggesting a neural crest origin of the tumour as this finding is shared with other neural crest tumours such as pheochromocytoma and neuroblastoma.9 15
in 1987 described the radiological findings of MNTI proposing that the teeth involved in the lesion appear to be floating within the radiolucent area of the tumour.
Microscopically, MNTI always has a distinctive histological character.10
A dense fibrous stroma supports a dual population of small neuroblast-like cells with hyperchromatic nuclei and sparse cytoplasm and large melanin-containing cuboidal epithelial cells, the latter arranged in alveolar or tubular structures. Ultrastructurally, two cell forms seen by light microscopy were recognised, with possible intermediate forms. The large polygonal pigmented cells showed desmosomal thickenings in the cell membrane and presence of melanin granules at different stages of maturation in the cytoplasm whereas the non-pigmented cells were small neuroblast-like cells with hyperchromatic nucleus, scanty cytoplasm and neurite-like cytoplasmic processes.12
Immunohistochemical studies to identify various tissue markers in MNTI were first reported in 1985. Melissari et al24
confirmed the neural crest origin of MNTI by using NSE, a marker for neuronal and peripheral neuroendocrine cells and neuroendocrine tumours and S100 protein stain found in glial tissue and in Schwann cells. The small neuroblast-like cells show positivity to CD56, NSE, synaptophysin and chromogranin and the large melanocytic cells react positively to a variety of cytokeratins, NSE, HMB45 and chromogranin. A few scattered cells are positive to S100 protein stain. This pattern shows evidence for neural, melanocytic and epithelial differentiation.13
Though MNTI is a benign lesion, a few cases have been reported where death occurred due to disseminated MNTI. A local recurrence rate of 15% after conservative excision was reported by Block et al25
in 1980 and malignant transformation rate of approximately 2% was suggested by Cutler et al26
in 1981. In a few cases reported as malignant, the histological features have taken on a neuroblastoma-like appearance. In spite of the potential for local recurrence, many authors believe conservative surgical treatment to be the treatment of choice as the debulking effect of surgery and initiation of the bodily defences suffice to curb the growth of the tumour. A more aggressive form of treatment comprises total resection and even radiotherapy and chemotherapy, or a combination of both.27
- The rapid clinical growth rate of the tumour could lead to the possibility of misdiagnosing melanotic neuroectodermal tumour of infancy (MNTI) as a malignant lesion with subsequent over treatment.
- A complete investigation of the patient should be performed before the treatment modality is finalised.
- A long-term follow-up with physical and radiographic examination at monthly intervals for the first postoperative year is essential to rule out recurrences.
- Permanent reconstruction of the maxillary alveolus and missing dentition should be considered in the long-term treatment protocol and may have to be delayed until after growth is completed. In the interim, transitional removable partial dentures may be necessary.
- The skills of an orthodontist, prosthodontist, oral surgeon, oral pathologist and/or dentist are required, for the correct diagnosis, treatment and rehabilitation of the patient and to correct any functional and cosmetic deformity.