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.