DISCUSSION
Neuroendocrine cells are specialized cells that exhibit characteristics of both endocrine cells and neurons. Neuroendocrine carcinomas originate from these cells 2. NETs have a reported incidence of 2.5–5 cases/100 000 people. Common primary sites are lungs and associated structures. Extrapulmonary SNECs account for only 2.5-5% of all SNECs, while head and neck events account for 10-16%.2 Reported cases of NETs in the oral cavity are scarce3.
Ki-67 is a cellular proliferation marker crucial for detecting tumour growth. The proposed WHO 2010 grading system divides NETs into three classes on the basis of mitotic count and Ki-67 index. They include Grades 1, 2, and 3. Grade 1 exhibit a low proliferative index with Ki-67 3% or 2 mitoses per 10 high power fields, Grade 2 exhibit moderate proliferative with Ki-67 3%-20% or 2-20 mitoses per 10 high power fields, and Grade 3 exhibit a high proliferative index with Ki-67 >20% or >20 mitoses per 10 high power fields. Another way of evaluating a tumour proliferation rate is to count the number of mitoses per unit tumour area. However, in tissue with limited volume, Ki-67 is more convenient to measure than mitotic count. The survival rate of patients who had G3 tumours compared to other classes was significantly lower. In the present case, it was a mandibular lesion with extensive distribution. Ki-67 values were 90%, consistent with clinical findings 4,5.
Histopathology and immunohistochemistry play a crucial role in the diagnosis of SNEC. It has typical histologic features of small cell carcinoma such as densely packed cells with sparse cytoplasm and hyperchromatic nuclei with finely divided chromatin and discrete nucleoli. It is often associated with extensive necrosis as well as high mitotic figures. The immunohistochemistry evaluation of these tumours indicates the presence of neuroendocrine markers, particularly synaptophysin and chromogranin A, and low-molecular-weight cytokeratins6,7. The present case showed a small cell carcinoma with the presence of synaptophysin and chromogranin A which is typical for small cell neuroendocrine tumours.
Diagnostic Imaging is an essential component, in staging and assessing treatment outcomes for NET patients. For the evaluation of NETs, CT scans are often the primary imaging modality. MRI is a supplementary modality. It is necessary to perform a systemic whole-body assessment utilizing PET/CT and scintigraphy after NETs are suspected or diagnosed to establish whether the tumour is primary or metastatic5.
A multimodal approach is needed to treat SNEC due to its aggressive nature and high rates of recurrence and metastatic spread. Surgery is not feasible for most patients due to disseminated disease at diagnosis. Therapeutic radiotherapy and chemotherapy are recommended in these cases. For extrapulmonary lesions, cisplatin and etoposide are typically used as chemotherapy, the same regimen used to treat pulmonary lesions7,8.
CONCLUSION This case report describes a case of a small cell neuroendocrine tumour extensively involving the right side of the mandible, diagnosed in an elderly woman. Although NETs are rare, it is important to differentiate NETs from other tumours in the region because of their therapeutic importance. Since there is a paucity of reported cases in literature, a detailed description of such unique cases is needed as it would aid in developing an overall diagnostic protocol.