tumour pathology Flashcards
what is a neoplasm
A neoplasm is an abnormal mass of tissue , the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in same excessive manner after cessation of the stimuli which evoked change.
Abnormal mass is purposeless, preys on the host and virtually autonomous.
Two fundamental features of neoplasm are unregulated growth and clonal genetic defects (derived from single cell and all the cells in the neoplasm are clonal related)
metastasis
spread to distant, non-contiguous site
Lymphatic metastasis (spread to lymph nodes)
Haematogenous metastasis (spread to lung, liver, bone, brain, etc)
Implantation in body cavities (Pleural and peritoneal metastasis)
benign neoplasms
Cohesive, expansile, well demarcated masses, do not invade or infiltrate surrounding normal tissue (can push local structures, put pressure on them but do not invade)
Usually progressive and slow growth (can be seen on clinical and radiological examination); may come to a standstill or regress; mitotic figures rare and normal - some benign tumours have higher growth rates than malignant tumours
Well differentiated; structure sometimes typical of tissue of origin
Do not metastasize
malignant neoplasms
Locally invasive, infiltrating surrounding tissue; sometimes may be misleadingly cohesive and expansile
Infiltrative borders - stellate, spiculated (Can be seen on radiological and histopathological examination).
Locally advanced malignant tumours are fixed to adjacent structures and not mobile. (Clinical examination – palpation of the tumour)
May grow slowly or rapidly; mitotic figures may be numerous and abnormal
Some lack of differentiation (anaplasia); structure often atypical
Metastasis - Frequent; more likely with large undifferentiated primary tumours
anaplasia
anaplasia- lack of differentiation
Abnormal nuclei - high nucleus to cytoplasmic ratio, hyperchromatic nuclei (due to replicating DNA), clumped chromatin, prominent nucleoli
Anaplastic nuclei may have multiple copies of chromosomes and therefore more DNA
pleomorphism
variation in size and shape of cells and nuclei, abnormal mitotic figures
benign epithelial neoplasms
Adenoma - derived from glandular epithelium
Cystadenoma - benign epithelial neoplasm with cystic or fluid filled cavity
Papilloma - benign epithelial neoplasm producing finger like projections
benign mesenchymal neoplasms
Fat – Lipoma Smooth muscle – Leiomyoma Skeletal muscle – Rhabdomyoma Cartilage – Chondroma Bone – Osteoma Blood vessels – Haemangioma Fibrous tissue - Fibroma
malignant neoplasms (nomenclature)
Carcinoma - arising from epithelial tissue
Adenocarcinoma - arising from glandular epithelium
Squamous cell carcinoma – arising from squamous epithelium
Small cell carcinoma – arising from neuroendocrine cells or pleuripotent stem cells
Melanoma – arising from melanocytes
Sarcoma - arising from mesenchymal tissue
Lymphoma - arising from lymphoid tissue
Leukaemia - arising from blood or bone marrow elements
definitions: mixed tumours, teratomas, blastomas
- Neoplasms with more than one cell type but arising from only one germ layer are called ‘mixed tumours’
- Neoplasms with more than one cell type and arising from more than one germ layer are called teratomas
- Neoplasms ending in ‘blastoma’ resemble primitive embryonic tissues, which are often paediatric neoplasms (e.g. Retinoblastoma, Neuroblastoma)
what is tumour grade?
Histologic parameter quantifying degree of differentiation
Well differentiated (low grade) tumours resemble mature normal cells of the tissue of origin
Poorly differentiated (high grade) tumours show little resemblance to tissue of origin
Limitations - Many tumours show intermediate differentiation, sampling error in small biopsies, interobserver variation for assessment of grade (subjective light microscopic interpretation)
what is tumour stage?
AJCC and UICC (TNM)
Size of the tumour, extent of invasion, lymph node involvement, distant metastasis
Important in planning appropriate treatment, prognosis, research and guidelines
what are the clinical manifestations of cancer?
Cancer can cause illness by Local invasion and impingement on local structures Ulceration, bleeding and infection Cachexia Paraneoplastic process
causes of neoplasia
Environmental causes – Chemicals, Oncogenic viruses, Radiation
Hereditary causes
carcinogen
An external agent that increases the incidence of malignant neoplasms, reduces their latency, or increases their severity or multiplicity – WHO
chemical carcinogens
- There are two steps: initiation and promotion
- An initiating carcinogenic agent irreversibly damages cell DNA (it is mutagenic) to start the process
- A promoting agent (which may be the same as the carcinogen) then acts (reversibly) to cause proliferation of a neoplastic cell clone, but there appears to be a “dose-threshold” concentration of promoter below which neoplasia will not occur.
Many chemical carcinogens are highly reactive electrophiles (have electron deficient atoms) that can react with nucleophilic (electron rich) sites in the cell, including DNA, RNA and protein. Direct carcinogens (direct acting alkylating agents) Indirect carcinogens (aka procarcinogens) - Metabolite is the active carcinogen
