Most patients present with a very rapidly growing mass that often gives a bluish appearance in the mouth. This is because the pigmentation in the cells appears blue through the overlying epithelium. By imaging studies, there is usually a large expansiveradiolucent mass without well defined borders. Calcifications within the mass may be seen. More than 70% involve the maxilla, while the mandible and skull are affected less often. There is often an elevated vanilmandelic acid level.
Pathogenesis
It is considered to be a developmental anomaly, and thus is congenital in presentation. It is thought to be derived from neural crest, which is one of the embryologic tissue types. The reason for this postulation is based on the expression of melanotransferrin.
Diagnosis
Macroscopic
Usually there is a smooth, firm mass, with mottled white-gray to blue-black cut surfaces. The overall size ranges from 1–10 cm with a mean size 3.5 cm.
Microscopic
The tumor is usually very well circumscribed but not encapsulated. There are two cell types present, arranged in alveolar or tubular configurations. There are centrally located, small, darkly staining cells comprising the majority of cells. These cells have a fibrillary cytoplasm surrounding round nuclei with coarse and heavy nuclear chromatin. These cells are surrounded by much larger polygonal cells that have open nuclear chromatin and abundant opaque cytoplasm that has granular melanin pigment. There is usually no hemorrhage, necrosis or increased mitoses.
Immunohistochemistry
The lesional cells will show cross reactivity with several different families of immunohistochemistry markers, including neural, melanocytic, and epithelial.
It is important in this age group to exclude other tumors that can have a similar appearance, such as rhabdomyosarcoma, lymphoma, Ewing sarcoma, or even a melanoma.
Management
Even though there is often a very dramatic and rapidly enlarging, destructive tumor, there is usually a benign clinical course after complete local excision with clear or free surgical margins. In rare cases, chemotherapy may be used for recurrent or residual tumors. Overall, the outcome is good, although it is quite unpredictable, with about 30% of patients have a recurrence. In about 10% of cases, metastasis may be seen.
Epidemiology
This tumor is exception, with fewer than 500 cases reportedworld wide. More than 95% of patients are less than 1 year of age at presentation, with about 80% less than 6 months. Females are affected more often than males.
