In Lymph Node Metastases

Cancer cells initially lodge in the marginal sinus, and then extend throughout the lymph node. Metastases may be confined to the lymph node, or may penetrate the capsule and infiltrate the perinodal tissue; this pattern of growth has been referred to as extracapsular spread (ECS). Extracapsular spread is further divided into macroscopic and microscopic ECS [62]; macroscopic ECS is evident to the naked eye during the laboratory dissection of the surgical specimen and is later confirmed by histological assessment. It usually involves not only the perinodal fibro-adipose tissue, but also the surrounding structures. Microscopic ECS is only evident on histo-logic examination and is usually limited to the adjacent perinodal fibro-adipose tissue.

Extracapsular spread is a significant predictor of both regional recurrence and the development of distant metastases resulting in decreased survival [109, 155, 175, 335, 337]. In some studies, ECS has been shown as a better predictor than the resection margins. It has therefore been suggested that ECS should be incorporated into the staging system for surgically managed patients [380]. Some studies, on the contrary, have not confirmed the independent prognostic significance of extracapsular spread [230, 280].

In some patients, an SCC in the soft tissue of the neck is found, with no evidence of lymph nodes being present. These soft tissue metastases may be the result of either total effacement of a lymph node by the SCC, or extra-lymphatic spread of the SCC [176].

It has been shown that the presence of soft tissue metastases is associated with an aggressive clinical course and poor survival [176, 368]. In a study of 155 patients, survival was significantly shorter for patients with soft tissue metastases than those without nodal metastases and those with nodal metastases without extracapsu-lar spread; it was similar to that for patients with lymph node metastases with extracapsular spread [176].

Distant metastases in patients with head and neck cancer are usually defined as metastases below the clavicle, and may be the result of lymphogenic or haematogenous spread. Lymphogenic spread results in distant lymph node metastases; the most commonly affected distant nodes are the mediastinal, axillary and inguinal nodes [7]. Haematogenous spread results in distant metastases, most commonly to the lung, liver and bones, followed by the skin and brain [84, 157, 198, 208, 337, 362, 387]. Metastases have been also described in the small intestine [384], spleen [3] and the cavernous sinus [362].

Distant metastases in head and neck SCCs are infrequent, but may occur in the late stages of the disease, with the reported incidence between 3 and 8.5% [337, 387]. Postmortem studies have shown a higher incidence of distant metastases, ranging from 24 to 57% [266, 325, 393].

The incidence of distant metastases depends on the site of the primary tumour, as well as the initial size of the tumour and the presence of nodal metastases [59, 198, 253]. The highest incidence of distant metastases has been reported in hypopharyngeal SCCs, followed by the SCCs of the tongue [198].

Most distant metastases become clinically apparent 2 years after diagnosis of the initial tumour. The average survival once distant metastases are diagnosed ranges between 4 and 7 months [208].

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