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Cards (57)
Cancer
in individuals ≤19 yr of age is uncommon representing only about
1%
of all new cancer cases in the USA
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Malignant neoplasms
remain the second most common cause of all deaths (
12.8
%) among persons 1–14 yr of age in the USA
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Pediatric cancers
Differ markedly from adult malignancies in both
prognosis
and distribution by
histology
and tumor site
Common childhood tumors are lymphohematologic, embryonal,
CNS
tumors,
soft tissue
tumors
Unlike adults epithelial tumors are
uncommon
in children
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Tumor incidence
is highest during early
childhood
and adolescence
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Percentage of different childhood tumors
Lymphohematopoietic
cancers - 40%
Nervous system
cancers - 30%
Soft tissue sarcomas
- 10%
Embryonic tumors
- 10%
Neuroblastoma
- 6-7%
Wilms tumour
- 6-7%
Retinoblastoma
- 3%
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Embryonal tumors, acute leukemias, non-Hodgkin lymphomas, and gliomas
Peak in incidence from
2–5
yr of age
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As children age
Bone
malignancies, Hodgkin disease, gonadal germ cell
malignancies
, and other carcinomas increase in incidence
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Oncogenes
Genes implicated in the development of
cancer
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Tumor suppressor genes
Important regulators of
cellular growth
and programmed
cell death
or apoptosis
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Mechanisms by which proto-oncogenes can be activated to oncogenes
1.
Amplification
2.
Point
mutation
3.
Translocation
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Tumor suppressor genes
Alteration in the regulation of tumor suppressor genes results in
cancer
Mutations in
P53
&
Rb
gene
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Knudson's
"
two-hit
" model
Inactivation of both alleles of a tumor
suppressor
gene is required for expression of a malignant phenotype
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Mechanism of cancer formation
Aberrant cellular growth
Signal transduction
Cell cycle control
DNA repair
Cellular growth and differentiation
Translational regulation
Senescence and apoptosis
Cancer stem cells
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Cell cycle
All cells at some point enter the
cell cycle
, whether during embryonic development or normal body maintenance<|>Cell growth occurs via
cell cycle
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Phases of the cell cycle
G0
- Cell is quiescent and withdraws from cell cycle
G1
- Genes actively direct synthesis of RNA and proteins
S
- DNA replication
G2
- Final growth and activity before mitosis
M
- The dividing phase of the cell cycle
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Cyclins
Groups of
proteins
that control progress through each phase of the cell cycle (produced by
proto-oncogenes
)
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Cyclin
inhibitors
Proteins that inhibit the activity of cyclins, thereby
inhibiting
cell growth and cell division (produced by
tumor suppressor
genes)
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Cell cycle turnover
Rapidly
dividing cells: epidermal, BM, epithelial lining of
GIT
, oropharynx
Slow
dividing cells: fibroblasts, osteoblasts, osteoclasts
Non-dividing
cells: striated muscle, nerve cells
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Cell cycle/growth stimulus
Internal signals:
growth
factors (tissue growth and
differentiation
, tissue injury)
External signals:
infections
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Apoptosis
A programmed physiologic process for normal cell
turnover
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Aberrant cell division
The primary characteristic of a cancer (
malignant
) cell, such a cell has lost the ability to control cell growth and the ability to undergo
apoptosis
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Properties of cancer cells
Uncontrolled growth
Invasion
Metastasis
Angiogenesis
Immortality
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Genetic risk factors for childhood cancer
Neurofibromatosis
Down syndrome
Beckwith-Wiedemann syndrome
Ataxia-telangiectasia
Li-Fraumeni
(
P53
) syndrome
Tuberous sclerosis
Xeroderma pigmentosum
Nevus basal cell carcinoma syndrome
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Viral risk factors for cancer
Epstein-Barr
virus (EBV)
Hepatitis B
virus
Hepatitis C
virus
Human papillomavirus
(HPV 16, 18)
Human herpes
virus 8
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Unlike adult epithelial malignancies, the environmental risk of developing cancer is
less
common in children
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Childhood leukemia
The most common
malignant
neoplasms in childhood, accounting for
41
% of all malignancies in children <15 yr of age
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Types of childhood leukemia
Acute lymphoblastic leukemia
(ALL) - 77%
Acute myelogenous leukemia
(AML) - 11%
Chronic myelogenous leukemia
(CML) - 2-3%
Juvenile chronic myelogenous leukemia
(JCML) - 1-2%
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Pathogenesis of childhood leukemia
Genetic
abnormalities
in a
hematopoietic
cell
Unregulated
clonal
proliferation
of cells
Growth
advantage over
normal
cellular elements
Increased
rate of proliferation
Decreased
rate of spontaneous
apoptosis
Disruption of
normal marrow
function and marrow
failure
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Childhood leukemia
Peak incidence
2–6
yr of age
More common in
boys
than in
girls
Chromosomal abnormalities associated with leukemia: Down syndrome, Bloom syndrome,
ataxia-telangiectasia
,
Fanconi syndrome
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Environmental factors for childhood leukemia
Ionizing
radiation
Drugs: Alkylating agents,
Nitrosourea
,
Epipodophyllotoxin
Benzene
exposure
Advanced
maternal
age
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In virtually all cases, the etiology of
ALL
is
unknown
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Exposure to medical diagnostic radiation
Increases the
incidence
of
ALL
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cell
ALL
Associated with
Epstein-Barr
viral infections
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In twins, if the first twin develops
leukemia
, the risk to the second twin is
higher
than in the general population
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Clinical features of childhood leukemia
Fever
Easy bruising
Epistaxis
Bleeding
from any site
Bone pain
Joint swelling
Lymphadenopathy
(50%)
Pallor
Weakness
Recurrent
infections
Opportunistic
infections
Purpuric
and
petechial
skin lesions
Mucous
membrane hemorrhage
Hepatosplenomegaly
Bone
or
joint
tenderness or joint swelling and effusion
Testicular
swelling
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Lab findings in childhood leukemia
Leukocyte
count (median 33,000, 75% <20,000)
Thrombocytopenia
(75% of patients)
Hepatosplenomegaly
(30-40% of patients)
CNS
symptoms (5% of patients)
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ALL classification
Based on morphologic,
immunologic
, biochemical, and cytogenetic features<|>French-American-British (FAB) system: L1, L2,
L3
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L1 ALL
Lymphoblasts
are small cells with scant
cytoplasm
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Clinical features of ALL
Nonspecific fever, easy bruising, epistaxis, bleeding from any site,
bone
pain,
joint
swelling
Lymphadenopathy
(50 percent)
Pallor
,
Weakness
, recurrent infections
Opportunistic
infections
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Clinical features of ALL
Pallor
Purpuric
and
petechial
skin lesions
Mucous
membrane hemorrhage
Lymphadenopathy
,
HSM
Bone
or
joint
tenderness or joint swelling and effusion
Testicular
swelling
View source
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