ONCOLOGY
CANCER
GENERAL OVERVIEW
TUMOUR DEFINITION
The tumour is defined as an abnormal new growth that grows by abnormally rapid cell proliferation,
which continues to grow in the absence of growth stimuli, it shows a partial or complete disruption of
structural organisation and functional coordination, and it usually
forms a distinct mass of tissue.
In physiological situation, if a tissue is undergoing to proliferation,
a pool of cells in the tissue will die. This equilibrium between cell
proliferation and cell death allows to maintain the volume of the
tissue constant. On the contrary, in tumour, there is an alteration
in the balance between cell proliferation and cell death towards a
promotion of the cell proliferation.
The tumours can be divided into two types, which are:
• Benign tumours: they are tumours composed of cells that
proliferate autonomously, but they do not invade
adjacent tissues and do not spread towards distant sites;
examples are warts (e. g. HPV), nevus, lipoma, and benign
parotid tumour; note that the dimension of a tumour is not related to its malignancy; the
expansive growth may compress adjacent tissues; the tumoral cells may become independent
of homeostatic control (e. g. adenomas may
produce hormones without stimulating
signals); it may be encapsulated into a fibrous
capsule.
• Malignant tumours (or cancer): they are
tumours composed of cells that proliferate autonomously and invade adjacent tissues; they
can spread to distant sites by entering blood vessels or lymphatic vessels, thereby forming
metastasis; examples are melanomas (i. e.
melanocyte tumours that spread in the skin
layers), pancreatic adenocarcinoma, and
melanoma metastases (e. g. liver, loss of
functionality in producing melanin).
PHYSIOLOGICAL ADAPTATIONS
The increase of the mass of a tissue due to cell proliferation is not always pathological and related to
tumours. Indeed, there is a distinction between adaptive cell responses and tumours. There are
different adaptive responses
that can be triggered by a
tissue, which are:
• Hypertrophy: it
consists in an increase
in cell dimension;
examples are the
hypertrophy of the skeletal muscle, typical in case of training.
• Hyperplasia: it consists in an increase in cell number; it occurs for instance in muscle cells and
in the thyroid gland (i. e. goitre).
• Metaplasia: it consists in a substitution of a specialised cell type with another different cell
type, which still belongs to the same lineage; an example occurs in the Barrett’s oesophagus,
in which the squamous epithelium of the oesophagus is converted into glandular epithelium;
, it is typical in patients that suffer from gastroesophageal reflux, and it can revert into
gastroesophageal cancer.
All these adaptations are reversible conditions since there is not an alteration of the cell genome.
They are physiological.
DYSPLASIA
The dysplasia is a pathological alteration in tissue architecture with variation in the cell dimension
and morphology (i. e. pleomorphism), abnormal nuclei (e. g. enlarged, irregularly shaped,
hyperchromic, etc.), and irregular arrangement of cells in the
tissue (i. e. loss of polarity). The dysplasia main increase the
risk of evolving into a malignant tumour.
An example of dysplasia may be observed in the uterine
cervix biopsy. It shows cells that are different in dimension,
morphology, and nuclei; the polarity of cells is completely
lost.
The dysplasia of the uterine cervix can be divided into
different phases according to its grade. Indeed, from normal tissue, low-grade squamous
intraepithelial lesion (LSIL) and high-grade
squamous intraepithelial lesion (HSIL) can be
formed. Normally LSIL reverts into normal
tissue, but if it forms HSIL there will be a high
susceptibility of cancer development. For that
reason, HSIL is used as pre-tumour marker to
detect uterine cancer predisposition.
Other examples of precancerous lesions are
actinic keratosis (UV light), oral leucoplakia
(herpesvirus infection), Barrett’s oesophagus (gastroesophageal reflux), atrophic gastritis
(Helicobacter pylori), intestinal polyps, ulcerative colitis, and cryptorchidism.
Furthermore, a typical sign that characterises malignant tumours is the presence of cachexia. The
neoplastic cachexia is a condition characterised by weight loss, apatia, and asthenia caused by the
activity of cytokines (e. g. TNF) produced by malignant tumoral cells.
CHARACTERISTICS BENIGN TUMOURS MALIGNANT TUMOURS
Growth rate Slow Rapid
Mitotic cells Rare Frequent
Differentiation High Low
Fibrous capsule Often present Absent
Type of growth Expansive Invasive
Damage of nearby tissues Compression Infiltration and substitution
Invasion in lymphatics Absent Frequent
Metastasis Absent Possible
Cachexia Absent Present
CANCER NOMENCLATURE
CANCER ORIGIN
The cancer that may be formed in the organism are several. The cancers can derive from different
tissues, and according to their origin they are divided into three main categories, which are:
• Carcinomas: they are tumours that have either an endodermal or an ectodermal origin;
examples are lung, breast, colon, bladder, and prostate cancer.
, • Leukaemia and lymphoma: they are tumours that have a haematological origin; they are
divided into leukaemia (tumoral cells in bloodstream), and lymphomas (tumours in lymphoid
organs).
• Sarcomas: they are tumours that have a
mesodermal origin; examples are fat, bone,
and muscle sarcomas.
A specific cancer nomenclature is used according to
the type of tumour that is present. Together with the
suffix that is given by the tumour origin (e. g.
carcinoma, sarcoma, etc.), prefix may be used to
indicates the cell or tissue of origin. Examples are
adeno- (gland), chondro- (cartilage), erythro-
(erythrocyte), hepato- (liver), melano- (melanocyte), and myo- (muscle).
EPITHELIAL AND MESENCHYMAL TUMOURS
The epithelial tumours can be either benign or malignant. In the epithelial lining, they can be polyp,
papilloma, wart (benign), and carcinoma. In glandular epithelium adenoma (benign) and
adenocarcinoma (malignant). Note that the
prefix indicates the site of origin, while the
suffix whether the tumour is benign (-oma) or
malignant (-carcinoma).
The mesenchymal tumours present as suffix -
oma if they are benign and -sarcoma if they are
malignant. Examples are fibrous connective
tissue tumours (fibroma, fibrosarcoma),
cartilage tumours (chondroma,
chondrosarcoma), adipose tissue tumours
(lipoma, liposarcoma), bone tumours
(osteoma, osteosarcoma), smooth muscle
tumours (leiomyoma, leiomyosarcoma), striated muscle tumours (rhabdomyoma,
rhabdomyosarcoma), and vascular tissue (angioma, angiosarcoma).
The tumour of the melanocytes can be benign (nevus), precancerous (dysplastic nevus), and
malignant (melanoma).
NERVOUS SYSTEM TUMOURS
The tumours of the nervous system present their own nomenclature. Most of them are benign, such
as meningiomas (37% of total nervous system tumours) and pituitary tumours (16%). Other, instead,
are malignant, such as glioblastomas (15%).
In paediatric cases, medulloblastoma (embryonic nerve
cells), neuroblastoma (embryonic nerve cells), and
retinoblastoma (retinoblasts) is the most common type
of malignant tumour. Note that medulloblastoma is one
of the few nervous system tumours that can cause
metastasis (migrate in spinal cord and nerves).
In adult cases, common benign tumours are meningioma
(meninges) and neurofibroma (Schwann cells), while
malignant tumours are astrocytoma, glioblastoma,
oligodendroglioma, and ependymal tumours. The
malignant brain tumours usually present a 5-year survival
that is less than 35%.
, HAEMATOLOGICAL TUMOURS
The haematological neoplasms are tumours that affect the circulation and the lymphatic organs. They
can be divided into two types, which are:
• Leukaemia: it is a haematological
tumour that derives from the
myeloid (platelets, erythrocytes,
granulocytes, monocytes) or the
lymphoid lineage (B- and T-
lymphocytes); in it, tumoral cells
are circulating in the blood; there
are two types of leukaemia, which
are acute and chronic leukaemia.
• Lymphoma: it is a haematological tumour that derives from the lymphoid lineage; it affects
the lymphatic organs; it is furtherly divided into two types, which are:
Non-Hodgkin lymphoma: they can have either an indolent or aggressive course.
Hodgkin lymphomas: they are characterised by binucleated tumoral cells, that are
called Reed-Sternberg cells.
The haematological neoplasms account for about 9% of all tumours in Italy. They are more frequent
in children, but fortunately they are more treatable in these patients.
CANCER INCIDENCE AND MORTALITY RATE
The five most frequently diagnosed tumours in Italy in 2019 (excluded skin cancer) are prostate, lung,
colorectal, bladder, and stomach cancers in males; while in females they are breast, colorectal, lung,
thyroid, and uterus cancers. The skin cancer is not considered
in studies on tumour incidence since it is highly common, and
it will represent the large majority of tumours.
As regards mortality rate, lung cancer is the tumour with the
highest mortality rate, followed by colorectal, prostate, liver,
and stomach cancer. In females they are breast, colorectal,
lung, pancreatic, and gastric cancer. A similar incidence is
observed in the US.
Overall, the cancers that present a higher incidence worldwide
are lung, prostate, colorectal, gastric, and hepatic cancer (due
to HBV or HCV infection), In
females the breast, colorectal,
lung, cervical, and thyroid
cancers are the ones with the
highest incidence. A similar
pathway is followed by the
mortality rate.
The risk of cancer incidence in the US is slightly increasing, while the
mortality rate is decreasing. Note that in the 1990-1995 there was a
large increase in the incidence of tumour in males
due to a higher detection of prostate cancer. The
prostate cancer was detected via the utilisation of a
marker, the prostate-specific antigen (PSA).
However, PSA is no longer used to diagnose prostate
cancer since it detects several false positive (e. g.
prostatitis, inflammation of prostate, etc.).
Moreover, this type of cancer grows slowly, and most
of patients will not develop severe symptoms.
