Week 6 Flashcards
Why is an understanding of cancer pathology important
Explains how cancers present clinically:
-rectal bleeding
-cutaneous mass
-jaundice
-haemoptysis, respiratory distress
Histopathological assessment important for:
-diagnosis: tissue confirmation required to diagnose cancer, tissue for subtyping the cancer, need to understand terms used in pathology reports
-prognosis: tumour grading and staging
-treatment: eg surgical resection, chemotherapy, radiotherapy
-additionally ancillary test eg molecular testing for prediction of chemo/immunotherapy
Neoplasia
A neoplasm is a mass of cell that:
-have undergone an irreversible change from normality and
-proliferate in an uncoordinated manner
-are partially or completely independent of the factors which control normal cell growth
Neoplastic growth persists even if the initiating stimulus is withdrawn
Neoplasm literally means “new growth”: a commonly used synonym for neoplasm is tumour (swelling)
Definition of cancer
A malignant neoplasm
Classifications of neoplasms
Behaviour - benign or malignant
Histiogenesis- tissue of origin/differentiation
Histological- sub typing within a tissue
Functional- hormonal secretion
Behaviour and histiogenesis are two most important features used in classifying neoplasms
Benign vs malignant neoplasms
Malignant neoplasms have the capacity for:
-local invasion into surrounding tissue
-spread to distant sites to form secondary deposits (metastases)
—metastasis occurs via two main routes (lymphatic and haematogenous)
The term cancer is used to describe all types of malignant neoplasm
Some neoplasm behave in an “intermediate” manner
-eg basal cell carcinoma of skin - invades local tissues, but doesn’t metastasise)
Liver haemangioma, benign neoplasm- well circumscribed
Neoplasm of vasculature structures of liver- haemangioma
Typical appearance of benign neoplasm: well circumscribed- doesn’t invade locally
Staging of malignant neoplasms
Staging= extent of spread (local or distant)
Numerous staging systems exist
-some are disease/organ specific
-a commonly used generic system is TNM
T=tumour
N=nodes
M=metastasis
Staging has important implications for prognosis and treatment
Neoplasia- tissue of origin
Epithelial
-most malignant neoplasms termed ‘carcinoma’ (eg skin, lung, GIT)
Mesenchymal tissue:
-many benign neoplasms eg soft tissue “lipoma”, muscle “leiomyoma”, blood vessels “haemangioma”
-if malignant termed “sarcoma”
-mesothelium- mesothelioma
Other:
-haemato-lymphoid neoplasms, termed “lymphoma” from lymph nodes or “leukaemia” if involving blood cells
-germ cell neoplasms- teratoma, Seminoma
Differentiation
Differentiation is the degree to which a neoplasm histologically resembles its tissue of origin
Benign neoplasms- always well differentiated (always closely resembles tissues of origin)
Malignant neoplasms- differentiation variable
Grading
Grading is a term used to describe the degree of differentiation
Grade 1- well differentiated
Grade 2- moderately differentiated
Grade 3- poorly differentiated
Grading has implications for prognosis and treatment
-poorly differentiated cancers behave more aggressively
-well differentiated cancers have better prognosis and certain well differentiated cancer eg prostate can be managed conservatively
Some malignant tumours are so poorly differentiated that it’s impossible to determine their histiogenesis. These neoplasms are called anaplastic
Classification of common neoplasms
Epithelium origin:
-squamous— squamous cell papilloma (Benign), squamous cell carcinoma (malignant)
-transitional- transitional cell papilloma (b), transitional cell carcinoma (M)
-glandular- adenoma (B), adenocarcinoma (M)
Mesenchyme:
-fat— lipoma (b), liposarcoma (M)
-fibrous tissue— fibroma (b), fibrosarcoma(m)
-smooth muscle -leiomyoma (b), leiomyosarcoma (m)
-skeletal muscle- rhabdomyoma (b), rhabdomyosarcoma (m)
-cartilage- chondroma (b), chondrosarcoma (m)
-bone- osteoma(b), osteosarcoma (m)
Thyroid carcinoma
Different behaviour according to histological subtype
Papillary: freq 75-85%, lymphatic spread (lymph node metastasis), very good prognosis 5 year survival>95%
Follicular: freq 10-20%, haematogenous spread (bone metastases), good prognosis 5 year survival >80%
Anaplastic: freq 5%, local invasion, poor prognosis (most dead within 1 year)
Classification of neoplasms functional
Classification according to substances produced
-endocrine neoplasms secreting functionally active hormones
-insulinoma= insulin producing pancreatic islet cell neoplasm
-prolactinoma= prolactin producing anterior pituitary neoplasm
Other tumours and tumour like conditions
Teratomas
Embryonic neoplasms
Hamartomas
Teratomas
Neoplasms derived from embryonic germ cells
Have the capacity to form representatives of all 3 germ cell layers (totipotential cells)
Teratomas occur in the following sites:
-ovary- usually benign
-testes- usually malignant
-midline structures (retroperitoneum, mediastinum)-behaviour variable
Embryonic tumours
Arise from neoplastic transformation occurring in the developing organ
Derived from multi-potential embryonic “blast” cells and given the suffix- blastoma
Frequently have divergent differentiation eg epithelial and mesenchymal
Majority present at or soon after birth. Commonest type of neoplasm in childhood
Most are highly malignant (but may respond well to aggressive treatment)
Examples:
-nephroblastoma (Wilma’s tumour)
-hepatoblastoma
Hamartomas
Not genuine neoplasms but tumour like malformations
Many present at birth and stop growing when the host stops growing
Examples: peutz Jeghers polyp, bronchial hamartoma, biliary duct hamartoma
Comparison between benign and malignant neoplasms
Essential differences
Gross appearance
Microscopic features
Growth characteristics
Effects on host
Essential differences between benign and malignant
Invasion: B=no, M=yes
Metastasis: B=no, M=yes
Gross appearance benign vs malignant
Shape: b=well circumscribed, m-irregular
Size: b=generally smaller, m=generally larger
Haemorrhage: b=unusual, m=common
Ulceration: b=unusual, m=common
Necrosis: b=unusual, m=common
Microscopic features benign vs malignant
Nuclear size: b=normal, m=enlarged
Nucleoli: b=small/inconspicuous, m=prominent
Pleomorphism and loss of polarity: b=absent, m=often marked
Mitoses: b=infrequent, m=frequent (may be atypical)
Differentiation: b=good, m=variable
Anaplastic carcinoma
Big nuclei
Prominent nuclei
Several mitoses
Growth characteristics benign vs malignant
Speed: b=slow, m=rapid
Spontaneous arrest: b=common, m=rare
Comparison between benign and malignant neoplasms effects on host
Mechanical pressure: b=yes, m=yes
Invasion: b=no, m=yes may damage vital structures
Metastasis: b=no, m=yes common cause death
Paraneoplastic syndromes : b=no, m=yes (esp lung cancer) neurological, haematological, endocrine, immunological, other
Death: b=very uncommon, m=frequent (if untreated)
Pathology as a clinical discipline
Specimens from living people
Approx 70% of hospital diagnoses based on pathology “tests”
-majority are simple tests (eg blood samples)
-others are more complex and invasive (eg biopsies, surgical resection, specimens, molecular biology tests)
Information also important for prognosis and treatment
Why is an understanding of tumour pathology important
Clinical presentation and natural history
Terms used to classify neoplasms and their clinical relevance
Treatment options
How are neoplasms classified
Behaviour- benign or malignant
Tissue of origin/differentiation
Histological subtypes
Knowledge of gross features helpful in distinction between benign and malignant lumps (clinical examination, radiology)
Benign= smooth, well circumscribed, mobile
Malignant= irregular, poorly defined, may be fixed to adjacent tissues
Fibroadenoma
Commonest benign breast neoplasm
Mostly occurs in young women <30
Smooth well circumscribed lumps, highly mobile on palpation (“breast mice”)
Breast carcinoma
Commonest malignant breast neoplasm
Commonest cause of cancer death in women
Mostly occur in older women (75%>50 years)
Irregular, poorly circumscribed lumps, rarely mobile on palpation (due to invasion of surrounding structures)
In which layer of the colon do majority of neoplasms arise
Mucosa
Colon carcinoma- clinical presentation
Caecum/ascending colon: often polypoid, rarely cause bowel obstruction, insidious presentation- eg anaemia, weight loss
Sigmoid colon: often stenosing, frequently cause bowel obstruction, typically present with alteration in bowel habit