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Poorly differentiated NEC arises most often in the supraglottis, but it also occurs in other parts of the larynx. It affects men more frequently than women, mostly between 50 and 70 years of age; most patients are heavy smokers. The most common presenting symptoms are hoarseness and dysphagia, frequently associated with painless enlarged cervical lymph nodes due to metastases. It may be associated with a paraneoplastic syndrome [108, 244].

Grossly, PD-NECs are submucosal nodular or polypoid masses, frequently ulcerated and cannot be distinguished from other laryngeal carcinomas.

Microscopically, laryngeal PD-NECs are identical to their pulmonary counterparts [243]. They are composed of closely packed small cells with hyperchromatic round, oval or spindle nuclei and very scant cytoplasm. Necroses, mitoses, as well as vascular and perineural invasion are frequently present. PD-NEC can also be composed of slightly larger cells with more cytoplasm. The mucosa is often ulcerated, but there is no carcinoma in situ or significant atypia.

Immunohistochemically, the tumour cells variably express cytokeratins and neuroendocrine markers, such as synaptophysin, neuron-specific enolase, chromo-granin, S-100 protein and CD56.

By electron microscopy, sparse neurosecretory granules are occasionally found, but they may be absent.

In the differential diagnosis, the possibility of a metastasis from the lung must be excluded. PD-NEC must also not be confused with the basaloid squamous carcinoma, malignant lymphoma, and malignant melanoma. Basaloid squamous carcinoma is composed of larger cells, contains areas of squamous differentiation, tends to stain for high molecular-weight cytokeratins, and is frequently associated with atypia of the overlying squamous epithelium. Malignant lymphomas characteristically express leukocyte common antigen and B- or T-cell markers, which are absent in PD-NEC. Malignant melanoma occasionally consists of small undifferentiated cells, thus resembling PD-NEC, but, in contrast to PD-NEC, it typically expresses S-100 protein, melan A and/or HMB45.

The clinical course is aggressive, characterised by early metastases to the regional lymph nodes and distant sites, especially to the lungs, bones and liver. In contrast to lung PD-NEC, laryngeal PD-NEC does not frequently metastasise to the brain.

Radiation with chemotherapy is the treatment of choice. Surgical therapy is not indicated because most patients have disseminated disease at presentation. The prognosis is poor, and the 2- and 5-year survival rates are 16 and 5% respectively [114, 135].

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