|Year : 2008 | Volume
| Issue : 2 | Page : 64-67
Primitive neuroectodermal tumor of the maxilla
Leena Dennis Joseph1, Ravi Kumar2, Kannan Senthil2, C Ravindran3, D Prathiba1
1 Department of Pathology, Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India
2 Department of Ear, Nose and Throat, Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India
3 Department of Oral and Maxillofacial Pathology, Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India
Leena Dennis Joseph
Department of Pathology, Sri Ramachandra Medical College and Research Institute, Porur, Chennai - 600 116
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Primitive neuroectodermal tumor (PNET) of the maxilla is a soft tissue sarcoma classically described under small round blue cell tumors. This tumor is commonly seen in the chest, pelvis, abdomen, and extremities; and rarely in dura, ovaries, cervix, etc. These tumors are rare in the head and neck area. We report a case of a 3-year-old girl presenting with a PNET of the maxilla.
Keywords: CD 99, maxilla, primitive neuroectodermal tumor, small round blue cell tumor
|How to cite this article:|
Joseph LD, Kumar R, Senthil K, Ravindran C, Prathiba D. Primitive neuroectodermal tumor of the maxilla. J Oral Maxillofac Pathol 2008;12:64-7
|How to cite this URL:|
Joseph LD, Kumar R, Senthil K, Ravindran C, Prathiba D. Primitive neuroectodermal tumor of the maxilla. J Oral Maxillofac Pathol [serial online] 2008 [cited 2019 Dec 14];12:64-7. Available from: http://www.jomfp.in/text.asp?2008/12/2/64/44580
| Introduction|| |
Primitive neuroectodermal tumors (PNETs) and Ewing's sarcoma belong to the family of soft tissue sarcomas. PNETs and Ewing's sarcoma share unique chromosomal translocation t(11;22)(q 24;q 12) leading to the formation of the EWS-FLI-1 fusion protein. They present clinically with localized pain and a mass, with or without generalized symptoms of fever, anemia, malaise; and on histopathology, as small round blue cell tumor.
| Case Report|| |
A 3-year-old girl presented with a swelling over the left side of the cheek. The swelling was noticed 2 weeks ago. The swelling progressively increased in size since then and was accompanied by two episodes of bleeding from the mouth. On external examination, there was a 4×4-cm swelling on the left side of the cheek, with the skin over the swelling being smooth. The swelling was of the same color as the surrounding skin, firm in consistency and with sharp well-defined margins. The swelling was nontender, with no local rise of temperature. There was neither any fever nor were there other constitutional symptoms like paresthesia, fatigue, etc. On opening the mouth, there was an ulceroproliferative growth of 4 cms size involving the left gingivobuccal sulcus, hard on palpation, with restricted mobility.
The patient underwent excision biopsy of the mass with adequate margins, and bleeding was controlled by pressure packing. The biopsy specimen was submitted for histopathological examination, which revealed a tumor composed of uniform small round cells with round nuclei containing fine chromatin, scanty clear or eosinophilic cytoplasm, and indistinct cytoplasmic membranes. The tumor cells were arranged in sheets, with a marked increase in mitotic count [Figure 1],[Figure 2],[Figure 3],[Figure 4]. There were neither any areas of necrosis nor was there evidence of any rosettes or any specific vascular pattern. The possibility of a small round blue cell tumor (SRBCT) was considered with a differential diagnosis of lymphoma, PNET, rhabdomyosarcoma, and a poorly differentiated carcinoma. Further immunohistochemical work-up was done for the final diagnosis. Immunohistochemistry showed CD45 [Figure 5], CD3, CD20 (lymphoma markers), cytokeratin [Figure 6] (marker for carcinoma), and desmin [Figure 7] (marker for rhabdomyosarcoma) to be negative. CD99 (MIC 2) was strongly positive [Figure 8] in the tumor cells, which confirmed the diagnosis of PNET. The patient was given chemotherapy, followed by radiation in another hospital. The patient was lost to follow-up.
| Discussion|| |
Primitive neuroectodermal tumor is a malignant neoplasm that originates from the cells of the primitive neural crest. It was first coined for a group of embryonal tumors located in the central nervous system (cPNET). More recently, the PNET concept has been expanded to include histologically similar, peripherally located tumors, referred to as peripheral PNETs [pPNET's]. Among the cPNET's are medulloblastoma, pineoblastoma, cerebral neuroblastoma, ependymoblastoma, medulloepithelioma, primary rhabdomyosarcoma, and atypical teratoid/rhabdoid tumor. The pPNET's are a part of the Ewing's sarcoma family of tumors, which include Ewing's sarcoma of bone, extraosseous Ewing's tumor, and primitive neuroectodermal tumor. Various synonyms, including peripheral neuroepithelioma, peripheral neuroblastoma, and Askin tumor, have been used to describe this entity.
PNET and Ewing's sarcoma are highly malignant tumors of children, adolescents, and young adults. This family of tumors comprise morphologically heterogenous group of tumors that are characterized by a nonrandom chromosomal translocation t(11;22)(q 24;q 12) leading to the formation of the EWS-FLI-1 fusion protein. This contributes to the pathogenesis of these tumors by modulating the expression of target genes.  These translocations can be detected by reverse transcriptase polymerase chain reaction (RT PCR) and fluorescence in situ hybridization (FISH).
This family of tumors includes small round blue cell tumors of the bone, soft tissue, and nerve with morphological attributes of the germinal neuroepithelium. Common sites involved are chest, pelvis, abdomen, and extremities. The other rare sites include craniospinal vault, including central nervous system, meninges, cranial and spinal nerve roots.  Its occurrence in the dura has also been reported by Dedeurwaerdere et al.  Cases of PNET have been reported in the lungs,  ovaries,  and pancreas.  This tumor is rare in the head and neck region. However, whenever these lesions occur in the head and neck area, they are found arising in the skull or mandible. Very few cases have been reported in the maxilla,  nasal cavity, ethmoid, temporal bone, or orbit. Rare isolated cases of PNET have been reported in the parotid.  This neoplasm manifests as a mass or swelling associated with pain and constitutional symptoms of fatigue and raised ESR. This at times leads to the mistaken diagnosis of osteomyelitis. Paresthesia and loosening of the teeth are the common features seen in Ewing's sarcoma of the jaws. In the head and neck, clinical symptoms depend on the site of presentation but invariably include pain and swelling of the surrounding structures due to mass effect. Fever is also common. Other reported symptoms and signs are site specific, including individual cranial neuropathies, exophthalmos, epistaxis, nasal obstruction, anosmia, neck masses, and headache.
Morphologically, PNETs are typically grouped with other small round blue cell tumors, including Ewing's sarcoma, lymphoma, neuroblastoma, and rhabdomyosarcoma.
Microscopically, EWSs/PNETs are composed of uniform small round cells with round nuclei containing fine chromatin, scanty clear or eosinophilic cytoplasm, and indistinct cytoplasmic membranes. The term Ewing's sarcoma has been used for those tumors that lack evidence of neuroectodermal differentiation, whereas the term PNET has been employed for tumors that demonstrate neuroectodermal differentiation.
Histologically, there is a spectrum of appearances which reflects the degree of neuroectodermal differentiation. Tumors at the poorly differentiated (Ewing's) end of the spectrum have scanty, pale cytoplasm and round-to-ovoid open nuclei with finely distributed chromatin pattern. At the opposite end of the spectrum, the cells may have somewhat eosinophilic cytoplasm and the chromatin pattern may be coarser with more frequent nucleoli. Mitotic figures are common in PNET, as are necrosis and endothelial hyperplasia. Diagnosis of PNET is aided by the presence of Homer-Wright rosettes.
Electron microscopy of EWS/PNET reveals cytoplasmic processes, along with filaments, microtubules, and neurosecretory granules. Immunohistochemistry shows tumor positivity with CD99 (MIC 2). The demonstration of immunoreaction with the p30/32 MIC 2 antigen (CD99) is however not confined to PNET/EWS. Studies have also demonstrated positive staining to CD99 in acute lymphoblastic lymphoma, related leukemias, alveolar rhabdomyosarcoma, and granulocytic sarcoma (acute myeloid leukemia).
The EWS/PNET spectrum shows immunohistochemical evidence of neuroectodermal differentiation by positivity for antigens like neuron-specific enolase (NSE), neurofilament, HNK 1 (Leu-7), S100, and synaptophysin. Molecular assays and polymerase chain reaction can be used to identify the common chromosomal translocation in these tumors.
Treatment modalities include surgical excision, chemotherapy, and radiotherapy. Peripheral PNETs are highly aggressive and have a propensity for local recurrence and metastasis to the lung, bone, and bone marrow. After a tissue diagnosis has been made, the patient should undergo a full metastatic work-up, including a chest x-ray, CT of the lungs, a bone scan, and bone marrow aspiration, to ascertain whether the tumor has metastasized. Bone erosion has been reported to be a common initial finding. Similarly, many affected patients have metastatic disease. Even though PNET is highly aggressive, it has been shown to be curable with multimodal therapy in some cases. Frequently used chemotherapeutic agents include cyclophosphamide, ifosfamide, vincristine, doxorubicin, and actinomycin D. Radiation is generally administered as an adjuvant therapy when surgical excision is incomplete, but it can also be used as a primary treatment for unresectable lesions. Although PNETs are believed to be radiosensitive, radiation is not believed to be adequate to cure macroscopic disease. This case is reported for the rarity of the location of the tumor, with an emphasis on the diagnosis of this entity for proper management.
To conclude, we have presented a case of a 3-year-old girl presenting with a rapidly growing soft tissue tumor in the maxillary vestibule. A clinical diagnosis of pyogenic granuloma, lymphoma, rhabdomyosarcoma, and PNET was suggested. Biopsy and histopathological examination revealed a tumor composed of sheets of small round blue cells; which had to be further categorized by immunohistochemistry, which was positive for CD 99, thus confirming the diagnosis of PNET. This emphasizes the importance of recognizing this entity when presented with a similar clinical scenario. The patient was lost to follow-up.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]