MNTI was first described by Krompecker in 1918 as a congenital melanocarcinoma. It was known by many names as its cellular origin was not clear. These names included pigmented ameloblastoma, retinal anlagetumor, melanotic adamantinoma, retinal choristoma,melanotic progonoma, melanotic epithelial odontoma,pigmented teratoma, atypical melanoblastoma,pigmented epulis and retinoblastic teratoma. Someauthors proved that this tumor causes a high urinaryexcretion of vanillylmandelic acid (VMA), suggestinga neural crest origin. Hence, they coined the term 'melanocytic neuroectodermal tumor of infancy'.
About 200 cases of MNTI have been reported until now. It is found to characteristically occur in the maxilla, more so from the intraoral side. Bone destruction and displacement of teeth often occur because of the intraosseous location in the maxilla. Other sites are the skull, mandible and the brain. The lesion is usually solitary and the mucosa over the lesion is usually intact. It has got a typical bluish color due to the presence of melanin. Although it is a benign tumor with a 2% chance of malignancy, it is locally aggressive. The majority of MNTI patients (there is no sexual predilection) present in the 1 year of life. The children present with swelling in the oral cavity, which often hinders feeding. The differential diagnosis is ameloblastoma, odontoma, odontogenic myxoma, fibroma, rhabdomyosarcoma, EwingÌs sarcoma, LangerhansÌ cell histiocytosis (LCH), non-HodgkinÌs lymphoma.
The plain radiograph of MNTI shows a well-circumscribed radiolucent lesion. As the tumor advances, it destroys the bone suggesting a malignant process. In its typical premaxillary position, the tumor can displace or destroy the developing dentition. CT scanning with intravenous contrast is often used to delineate the margins of osseous involvement. Additionally, MRI can be used to evaluate the bony extent of the lesion. Most MNTIsappear as typical soft tissue tumors with nonenhancing heterogeneous tissue density.
Histopathology shows biphasic pattern with the larger pigmented, melanocyte-like cells and smaller, nonpigmented neuroblast-like cells. Immunohistochemistry (IHC) is positive for cytokeratin, synaptophysin, HMB45, NSE, epithelial membrane antigen, glial fibrillary acidic protein and Leu-7.
The treatment of choice in MNTI is usually complete surgical excision. This treatment can usually be accomplished with a partial maxillectomy by using a Weber-Fergusson incision and a facial degloving approach. The adjacent bone and developing teeth must be sacrificed to get an at least 5 mm margin of healthy tissue. The average local recurrence rate is 15-20%. Radiotherapy and combination chemotherapy including vinblastine, ifosphamide, etoposide, cyclophosphamide, doxorubicin and dactinomycin has been advocated for inoperable recurrence or margin-positive resection. A high index of suspicion is necessary to diagnose this tumor and close follow-up is necessary to detect recurrence. Permanent reconstruction can be done after growth is completed.
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