world cancer report - iarc

structures such as bone, muscles and skin
may be evident. Cancers of the oral cavity
may be preceded by, and present with, leukoplakias
(Fig. 5.92) or with mucosal rigidity
and fibrosis, restricted mouth opening and
tongue mobility (oral submucus fibrosis).
Some 5-15% of patients with cancer of the lip
mucosa present with lymph node metastases,
compared with more than 50-70% of
those with tongue and floor of the mouth
cancers. Distant metastases from oral cancer
are uncommon. A careful oral examination
and palpation of the neck leads to diagnosis,
which is confirmed by biopsy.
Oral visual inspection in high-risk individuals
leads to early diagnosis of oral precancer
[8,9]. However, the effectiveness of organized
screening in reducing incidence of and
mortality from oral cancer remains to be
established.
An asymptomatic high neck mass in an adult
is frequently associated with a primary
oropharyngeal (tongue base and tonsil) or
hypopharyngeal primary tumour. Fine needle
aspiration biopsy and careful direct laryn- goscopy in order to identify the primary
tumour are mandatory. Frequently, a surgical
panendoscopy with tonsillectomy is indicated.
Patients with pharyngeal cancers may
complain of difficulty in swallowing and
hoarseness of voice, particularly in advanced
stages. The early symptoms of laryngeal cancer
are hoarseness with dysphagia, pain and
a neck mass. In most cases, the first sign of
nasopharyngeal cancer is a mass in the neck
(due to lymph node metastasis). Because the
tumour is close to the foramina through
which several cranial nerves pass, there may
be signs due to their compression, as well as
pain, blocked Eustachian tubes and nasal
stuffiness. Early detection of nasopharyngeal
cancer by screening for elevated antibody
titres to Epstein-Barr virus has been widely
performed in populations of Southern China,
although so far, it is not known whether this
procedure can prevent deaths.
Fig. 5.91 A paan-tobacco chewer in Kerala, South
India, with ingredients for betel quid (betel leaf,
areca-nut, lime and tobacco). This habit is associated
with a high risk of oral cancer.
234 Human cancers by organ site
< 0.4
< 0.6
Fig. 5.90 The global incidence of nasopharyngeal cancer in men. This cancer is very common in Southern
China.
Pathology and genetics
Most cancers of the head and neck are squamous
cell carcinoma, which may be poorly,
moderately or well-differentiated, according
to the degree of keratinization (Fig. 5.94).
Other variants of squamous cell carcinoma
include verrucous carcinoma, sarcamoid
squamous cell carcinoma and lymphoepithe-
< 0.8
< 1.9
Age-standardized incidence/100,000 population
< 25.2
lioma [10]. The vast majority of nasopharyngeal
cancers in endemic regions is comprised
of non-keratinizing and undifferentiated
histological types, whereas in non-endemic
countries, some 30-50% are keratinizing
squamous cell carcinomas [11].
Conditions carrying increased risk of head
and neck cancer include epithelial differentiation
disorders, such as dyskeratosis congenita,
and DNA repair deficiency syndromes
such as Blooms’ syndrome, Fanconi
anaemia, ataxia telangiectasia and xeroderma
pigmentosum (Carcinogen activation and
DNA repair, p89).
A strong genetic component to the risk of
developing nasopharyngeal cancer is evident.
Migrant populations of Chinese or
North African origin appear to retain their elevated
risk, as do their children, born in a new
host country. An association between human
leucocyte antigen (HLA) profile and risk of
nasopharyngeal cancer has been reported,
and a study of affected siblings in Singapore
identified a gene locus close to HLA with a
20-fold increased risk for nasopharyngeal
cancer.
Cytogenetic abnormalities have been reported
in head and neck squamous cell carcinoma,
including gain or loss of the Y chromosome
and abnormalities at other loci; very