Melanotic Neuroectodermal Tumor of Infancy: the Use of Immunohistochemical Analysis.

The Melanotic Neuroectodermal Tumor of Infancy (MNTI) is an asymptomatic, pigmented neoplasm characterized by a fast and locally aggressive growth along with a rare tissue formation. In the diagnostic process, the use of imaging exams can suggest a local destruction suggestive of malignancy, a sign of bone remodeling and expansion. Therefore, as any early diagnosis minimizes risks and improves the prognosis of treatment for the patient, the aim of this study was, based on a clinical case report, to corroborate the use of histopathological analysis associated with immunohistochemistry. Thus, we conclude that the immunohistochemical exam is of great importance for a better complementation of the MNTI diagnosis process. In addition, it can reveal signs of possible aggressive growth.

Introduction

The Melanotic Neuroectodermal Tumor of Infancy (MNTI) is an asymptomatic, pigmented neoplasm characterized by a fast and locally aggressive growth, in addition to a rare tissue formation (-).

It predominantly affects individuals in the first year of life, with 90% of the cases of this pathology occurring in the head and neck region, most commonly in the maxillary bone (, -).

This tumor originates from the neural crest, due to a biphasic population of neuroectodermal melanocytic, primitive cells and an epithelioid cell component with an abundance of pigments (, , , , , ).

In the diagnostic process, the use of imaging exams can suggest a local destruction, suggestive of malignancy, that is, signs of bone remodeling and expansion [8]. However, along with these tests, a histopathological analysis is needed and essential. Additionally, immunohistochemistry is useful in the diagnosis of MNTI (, , , ).

Therefore, since any early diagnosis minimizes the risks and increases the treatment prognosis for the patient, the objective of this study was, from a clinical case report, to corroborate the use of histopathological analysis associated with immunohistochemistry. The aim was also to briefly address the MNTI characteristics of the present clinical report in association with other studies in the literature.

Case Report

An 8-month-old male child was taken to a dental office with an expansive lesion in the oral cavity (Figure 1). The patient's mother reported the appearance of this alteration in the 3rd month after birth and of rapid growth. The patient had no previous serious pathologies. On physical examination, an increase in volume in the anterior region of the maxilla was observed, being characterized as a fixed nodular lesion with similarly colored mucosa in the surrounding area. In addition, its growth did not cause rigidity. Also, there was no pulsation, and no production of liquids.

Figure 1

Photo showing a lesion in the oral cavity. Source: personal archive.

An excisional biopsy was indicated. Subsequently, the histological sections revealed a fragment of mucosa covered by parakeratinized stratified pavement epithelial tissue. In the lamina, there was a neoplasm organized in nests, tubules and alveolar structures intermingled with dense stroma. Neoplastic cells presented a biphasic pattern. In areas, some nests of small and round cells were noted, exhibiting sparse hyperchromatic cytoplasm, while in other areas, epithelioid and cuboid cells were noted, exhibiting cytoplasm and light nuclei and dark brown granules of melanin pigment (Figure 2).

Figure 2

Histological sections in hematoxylin and eosin showing a neuroectodermal lesion.

On immunohistochemical examination, neoplastic cells were moderately positive for anti-CD99 antibody, stromal cells were diffusely positive for anti-Vimentin antibody. The proliferative index was evaluated using, for this purpose, the Ki-67 antibody, which was shown to be less than 5%. Neoplastic cells were negative for anti-S100 and BRAF-V600E antibodies (Figure 3). Having combined clinical, morphological and immunohistochemical characteristics, a final diagnosis of melanotic neuroectodermal tumor of infancy (MNTI) was established.

Figure 3

Anti-CD99 immunohistochemical test with moderately positive labeling (A – G), diffusely positive for anti-Vimentin (H – M), proliferative index less than 5% with Ki-67 (N – P) and negative cell labeling for anti-S100 and BRAF-V600E (Q – S).

According to the literature, MNTI occurs more frequently in the gnathic bones, in younger patients, with a predilection for males and with some peculiar clinical features. Several studies in the literature have reported similar characteristics related to this neoplasm, as can be seen in Table 2:

Table 2

- Epidemiological data and clinical characteristics

Author	Case Report	Epidemiology	Clinical Characteristics
Wu et al. ( 10 )	Case report of a 3-month-old newborn with remarkable tumor growth in 4 days without previous trauma.	70% of cases are located in the maxilla, followed by the cranial, mandibular and cerebral regions.	Fast growing, pigmented, firm, sessile tumor with malignant potential.
Moreu et al. ( 3 )	Clinical research with 11 patients aged (months) ranging from 0 to 5 months and mean age of 3.18 months.	Prediction for the head and neck area, especially in the jaw bone.	Painless, sessile, pigmented (black or blue) and non-ulcerated lesion.
Unsal; Yançin ( 9 )	A 6-month-old male child with increased mandibular volume.	It affects more the head and neck region. And it predominantly affects the maxilla (70 to 80%), skull (10%), mandible (6%) and brain (4%). In addition to the predominance in babies.	It presents as a rapidly growing, locally destructive, painless, immobile, black, brown, or blue pigmented swelling.
Pontes et al. ( 5 )	Literature review.	Greater predominance in gnathic bones and slightly affect males (1.32: 1).	More satisfactory prognosis in younger patients, due to the size of the pathology and less chance of metastasis.
Santos et al. ( 2 )	Anterior maxillary growth in a 6-month-old girl	Prevalence in gnathic bones (maxilla) in males and occurs in the first year of life, especially in the first months.	Rapid growth, invasive and causing deformities. Possibly malignant transformation and bone metastasis.
Soles et al. ( 8 )	Literature review.	Greater predominance in craniofacial bones (maxillary) and male predilection.	Firm, lobulated change, well-defined mass, bluish-black hue. In addition to showing rapid growth and local infiltration into adjacent tissues.
Ren et al. ( 4 )	Literature review.	Higher prevalence in cranial bones, observed in men and women, in addition to being diagnosed in the first years of life.	Progressive, asymptomatic growth and firm edema, with an intact epithelial surface.
Tiwari; Yadav ( 6 )	3-month-old girl with intraoral swelling and progressive growth and firm consistency.	More commonly in the craniofacial region, mainly the maxillary bone, followed by the skull, mandible and predilection in children under 1 year of age.	Pigmented and benign neoplasm, with high potential for rapid growth and locally destructive.
Ebel et al. ( 1 )	Case report of a 4-month-old boy with MNTI in the skull and 2-week rapid growth	Greater involvement in the maxillary region, followed by the cranial region.	Rapid development, without symptoms, pigmentary and invasive edema.
Mengide et al. ( 11 )	Extra-axial growth in the skull of an 8-year-old boy complaining of headache for about 3 months.	The most common location of the tumor is the craniofacial region, although other regions are described. Mainly in patients under 1 year of age.	Solid and painless lesion, in addition to being pigmented and is a neoplasm causing deformity in regions of appearance.

The table summarizes some clinical cases with the epidemiological and clinical characteristics of MNTI reported by the corresponding authors.

Source: Done by the authors.

Regarding the immunohistochemical peculiarities and the results of interactions with agents for the individual characterization of pathology, several studies in the literature have also reported the properties that are able to distinguish MNTI from other lesions, as can be seen in Table 3:

Table 3

- Immunohistochemical characteristics described in the literature.

Author	Anatomopathology / Immunohistochemistry Characteristics
Souza et al. ( 12 )	The immunohistochemical profile of MNTI is generally positive for cytokeratin and HMB45 and negative for S100. And Ki-67 and CD99 expressions are quite uncommon and may be related to more aggressive tumor growth.
Albuquerque et al. ( 13 )	Small cells of neural origin are confirmed by positivity for NSE, synaptophysin and chromogranin. And cells of ectodermal origin can be confirmed by the positivity of EMA, CK, HMB-45.
Cui; Mao; Liao ( 14 )	Smaller round cells were melanoma-associated antigen 45 (HMB45) / vimentin / epithelial membrane antigen (+), no significant glial fibrillary acid protein staining (GFAP) / neuron-specific enolase (NSE) / synaptophysin (+), and the largest cells were cytokeratin (CK) / S-100. Scattered cells exhibited desmin immunoreactivity and ~2% of cells were Ki-67 (+).
Batta et al. ( 7 )	Larger epithelioid cells stain positively with cytokeratin, vimentin and HMB-45, reflecting epithelial and melanocytic differentiation, in addition to generally not reacting with S-100 protein, helping to differentiate tumors such as melanoma. Smaller cell nests in MNTI are often positive for neurogenic markers such as synaptophysin, neuron-specific, enolase, and glial fibrillary acidic protein.
Strieder et al. ( 15 )	Larger cells express cytokeratins (CKs), epithelial membrane antigen (EMA), glial fibrillary acidic protein (GFAP), S100 and HMB45 protein, and smaller cells express CD56 and synaptophysin; both cells express neuron-specific enolase (NSE), PGP 9.5 and chromogranin A.
Wu et al. ( 10 )	The epithelioid component of large cells shows a small to moderate amount of eosinophilic cytoplasm and is positive with pancytokeratin and HMB45 immunostaining. The small blue primitive cell component does not show appreciable cytoplasm and is positive for synaptophysin.
Moreau et al. ( 3 )	In HE staining, a fibrocollagenous stroma surrounding an epithelioid and neuroblastic component organized in lobules or alveolar structures. And the neuroblastic component was discrete and masked by a large melanin-rich epithelioid component.Epithelioid cells expressed epithelial and melanocytic markers (AE1/AE3; and melan A, PS 100 and HMB 45, respectively).
Nicosia et al. ( 16 )	They are usually positive for cytokeratin, vimentin, epithelial membrane antigen, HMB-45, glial fibrillary acidic protein, and specific neuronal enolase.
Unsal; Yalçin ( 9 )	The largest fraction of epithelioid cells expressed a number of cytokeratins - in most patients HMB-45, but rarely S-100.8 protein. Neuroblast-like cells are positive for neuron-specific enolase, CD 56, glial fibrillary acidic protein and synaptophysin, and melanogenic cells are positive for HMB-45, epithelial antigen membrane antigen, cytokeratin and vimentin.
Emmerling; York; Caccanese ( 17 )	There is identification of immunohistochemical markers, such as cell population frequently expressing cytokeratins, HMB-45 and vimentin, while S100 is much less common. And the small cell population usually expresses synaptophysin but is negative for another neuroendocrine marker, chromogranin A.
Santos et al. ( 2 )	Other markers, such as HMB45, Melan A, cytokeratin, and neuroblastic markers, such as synaptophysin and neuron-specific enolase, can help in diagnosis.
Soles et al. ( 8 )	The cells present are positive for vimentin and neuron-specific enolase and negative for S100. Larger melanogenic epithelioid cells are commonly positive for cytokeratins and some differentiating markers of melanocytes (HMB-45, dopamine b-hydroxylase, etc.). Smaller neurogenic cells are positive for synaptophysin and negative for cytokeratin, in addition to being positive for glial fibrillary acidic protein (GFAP), but rarely for neurofilament and CD99.
Atarbashi-Moghadam Et Al. ( 18 )	Epithelioid cells are positive for cytokeratin, HMB-45 and NSE. Smaller cells are generally positive for NSE and CD56 and sometimes synaptophysin. Furthermore, MNTI are not expressed in the S-100 protein. Larger epithelioid cells express MDM-2, cyclin D1 and A.
Ebel et al. ( 1 )	Immunohistochemically positive staining for markers such as HMB-45, synaptophysin and cytokeratin strengthens the diagnosis. A marker to differentiate between benign and malignant tumors does not exist so far.

The table summarizes some histopathological and immunohistochemical characteristics of MNTI based on studies in the literature.

Source: Done by the authors.

Discussion

As previously reported, MNTI, in several studies, shares similar characteristics, which were also present in this case report. Furthermore, the patient's sex fits the predilection for a gender reported in the literature, with involvement in the first year of life. Also, regarding the characteristics of the lesion in the present study, these were similar to the literary findings, such as rapid and expansive growth with regional anatomical deformation; rigid and fixed lesion; in addition to the predilection for the maxillary bone (Table 2). However, it was observed that there was no pigmentation of the adjacent tissues surrounding the tumor lesion.

The diagnosis of MNTI can be performed mainly by radiological characteristics in association with histopathological examinations (, ). However, immunohistochemical analyses and molecular studies are useful and can contribute to the diagnosis of this neoplasm, especially in difficult cases and particularly in small biopsies with the possibility of differentiating this pathological change from other tumors present in childhood (-, ).

Thus, some immunohistochemical characteristics have been described by several researchers by exposing pathological MNTI tissue to some reagents, such as cytokeratin, HMB45, S100, Ki-67 and others (Table 3) (-).

Positive anti-CD99 and anti-vimentin antibodies were observed in the present study and are reported in the literature as immunohistochemical characteristics of MNTI, in addition to anti-S100 antibody negativity (-, , , , ) (Table 1 and 3). Besides, the prophylactic index with the use of the ki-67 antibody observed was similar to the study by Cui, Mao and Liao (), with the value lower than 5%, but different from the study by Moreu et al. (), with a mean value of 18%, in a survey of 11 patients (0 to 30%).

Table 1

Immunohistochemical Result

Antibodies	Result
Anti-CD99	+
Anti-Vimentin	++
Anti-S100	-
BRAF-V600E	-

Source: Done by the author.

According to Souza et al. (), positivity for the Ki-69 and anti-CD99 antibody, which was also observed in the present clinical case, may suggest an aggressive tumor growth, thus, giving a possible plausible explanation for the rapid growth of the tumor, usually in about 3 months.

Although histological evaluation is important for the final diagnosis of a pathological lesion, in cases of MNTI it is a poor indicator of clinical behavior (). However, immunohistochemical analysis provides some information about the aggressiveness of these tumors ().

Thus, with the rapid growth of MNTI, its malignant potential, in addition to recurrence rates, an early diagnosis is essential (). Therefore, immunohistochemical analyzes have become important because they can help confirm a melanotic neuroectodermal tumor of infancy diagnosis (, , ).

Conclusion

In conclusion, the immunohistochemical exam is of great importance for a better complementation of the MNTI diagnosis process. In addition, it can help detect any serious signs and symptoms of potentially aggressive growth.