Sinonasal undifferentiated carcinoma

Definition

A highly aggressive and clinicopatholog-ically distinctive carcinoma of uncertain histogenesis that typically presents with locally extensive disease. It is composed of pleomorphic tumour cells with frequent necrosis, and should be differentiated from lymphoepithelial carcinoma and olfactory neuroblastoma.

ICD-O code 8020/3

Synonym

Anaplastic carcinoma Epidemiology

The tumour is rare, with fewer than 100 reported cases. The age range is broad (third to ninth decade), and the median age is in the sixth decade {350,1216}. There is a male predominance (2-3:1).

Etiology

The neoplasm is typically negative for Epstein-Barr virus {350,1216}. Some cases have occurred after prior radiation therapy for nasopharyngeal carcinoma {1216}.

Localization

The nasal cavity, maxillary antrum, and ethmoid sinus are typically involved alone or in combination. The neoplasm also commonly extends to other contiguous sites.

Clinical features

Patients have multiple nasal/paranasal sinus symptoms, usually of relatively short duration, including nasal obstruction, epistaxis, proptosis, periorbital swelling, diplopia, facial pain, and symptoms of cranial nerve involvement.

Macroscopy

The tumour is usually larger than 4 cm. It is fungating, with poorly defined margins, bone destruction, and invasion of adjacent structures {2038}.

Tumour spread and staging

In addition to involvement of multiple sinuses, the neoplasm destroys sinus walls and orbital bones. Penetration into the cranial cavity is frequent. Less often, there is extension into the nasopharynx or oral cavity. The tumour can metasta-size to cervical lymph nodes and distant sites (such as liver, lung, bone) {1216}.

Histopathology

Sinonasal undifferentiated carcinoma forms nests, lobules, trabeculae and sheets, in the absence of squamous or glandular differentiation. Severe dyspla-sia of the overlying surface epithelium has been noted in a few instances. The nuclei are medium to large-sized, surrounded by small amounts of eosinophilic cytoplasm that lacks a syn-cytial quality. The nucleoli are variable in size, but most often, they are single and prominent. The mitotic rate is very high and there is often prominent tumour necrosis and apoptosis. Lymphovascular invasion is often prominent.

Immunohistochemistry

The carcinoma is immunoreactive for pan-cytokeratins and simple keratins (CK7, CK8 and CK19), but not CK4, CK5/CK6 and CK14 {801}. Less than half of the cases have been reported to be positive for epithelial membrane antigen, neuron specific enolase, or p53 {350}. The tumour is negative for CEA, while positivity for synaptophysin, chromo-granin, or S100 protein is only rarely observed {350,1216}.

Electron microscopy

Ultrastructurally, cells with occasional small desmosomes and rare dense core granules have been noted {819}.

Histogenesis

This is a tumour of uncertain histogenesis, but with unique clinicopathologic characteristics. It should be differentiated from other specific types of carcinoma and non-epithelial tumours with round cells.

Prognosis and predictive factors

Despite aggressive management, the prognosis is poor, with median survival of less than 18 months {350,1216}, and 5-year survival of less than 20% {856}. Recent results suggest that more promising outcome may be achieved by combining chemoradiation and radical resection {1802}.

Fig. 1.10 Sinonasal undifferentiated carcinoma. A Small nests of tumour cells with or without interconnections are frequently observed. B The cells usually have prominent nucleoli. The mitotic rate is high. C Conspicuous invasion of vascular spaces.

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