Small Cell Neuroendocrine Carcinoma

required for diagnosis [176]. Before placing a tumour within this category, a differential diagnosis of a primary tumour from the lung must be ruled out.

This type of tumour has been well documented in various head and neck territories, mainly in the parotid gland and in the larynx. In the sinonasal tract, where they are distinctly uncommon, small cell neuroendocrine carcinomas have been less precisely characterised, and so far no unanimous consensus has been reached with regard to the way they have to be separated from other small cell tumours, either round or undifferenti-ated, occurring in this region [51, 132, 151, 191, 208, 210, 229, 264]. Table 2.2 provides the current criteria most widely accepted for their recognition.

Small cell neuroendocrine carcinoma of the sinona-sal region is considered to derive from cells with neuroendocrine differentiation occasionally found in the se-romucous glands. In some cases the tumour grows surrounding the seromucous glands of the lamina propria, as if it were originating from them. They give rise to nests, cords and sheets of small, undifferentiated cells, with moulded nuclei and scanty cytoplasm. Immuno-histochemistry exhibits a positive reaction for low molecular weight cytokeratins and EMA, as well as variable positivity for neuron-specific enolase, Leu-7, CD56, syn-aptophysin and chromogranin. At least two neuroendocrine markers should demonstrate positivity [199]. Diligent searching and expert hands usually demonstrate neurosecretory granules by electron microscopy.

Although its prognosis seems to be somewhat better than that of SNUC, or for similar tumours of the lung, small cell neuroendocrine carcinoma is a high-grade malignancy. Treatment should be a combination of surgery and radiotherapy, plus chemotherapy.

Fig. 2.10. Sinonasal undifferentiated carcinoma (SNUC) a Extensive neoplastic growth invading ethmoid, orbit and sphenoid at the left and also the right ethmoid. Courtesy of Prof. J. Traserra, Barcelona, Spain. b Nests of small to intermediate epithelial cells showing markedly atypical nuclei and areas of necrosis. c Frequent foci of intra-vascular invasion

ICD-O:8041/3

This is a high-grade malignant epithelial tumour with histological features similar to small cell carcinoma of the lung [226]. Variable degrees of neuroendocrine differentiation may be demonstrable by electron microscopy or immunohistochemistry, but have not always been

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