MoD session 8: neoplasia 1 Flashcards
Define neoplasm
An irreversible, abnormal growth of cells that persists after the initial stimulus is removed.
Define malignant neoplasm
An irreversible, abnormal growth of cells that persists after the initial stimulus is removed AND that invades the surrounding tissue with potential to spread to distant sites. A.k.a cancer
Define tumour
Any clinically-detectable lump or swelling. One type of neoplasm
Define metastasis
A malignant neoplasm that has spread from its original (primary) site to a new, non-contiguous (secondary) site
Define dysplasia
A pre-neoplastic alteration in which cells show disordered tissue organisation. NOT neoplastic as change is reversible (as is the result of a stimulus, rather than being autonomous); can however change into carcinoma in situ (cancer that hasn’t invaded basement membrane), then invasive carcinoma (invades basement membrane)
Characteristics of a benign tumour
Remains confined to site of origin; does not produce metastases
Grows in a confined local area
Pushing outer margin (pushes and squashes rather than invades and destroys, so rarely dangerous)
Cells are well-differentiated: closely resemble parent
Characteristics of a malignant tumour
Irregular outer margin and shape
May have areas of necrosis (often grows away from blood supply) or ulceration (break in epithelial surface)
Range from well to poorly-differentiated: differentiation is indicated by grade. High grade=poor differentiation and for many this correlates with prognosis
What does anaplastic mean?
Cells with no resemblance to any other tissue
What changes are seen with worsening differentiation?
- cells have increasing NUCLEAR:CYTPLASMIC RATIO
- HYPERCHROMASIA: increased nucleus staining
- more MITOTIC FIGURES
- variation in size and shape of cells and nuclei: PLEOMORPHISM
How do mutations cause neoplasia?
Accumulation of mutations in somatic cells
INITIATORS (mutagenic agents) and PROMOTERS (cause cell proliferation) are needed to cause an expanded monoclonal population of mutant cells. Main initiators are chemicals/infection/radiation but some of these can also act as promoters
Mutations can be classed as passenger mutations (in genes unimportant to proliferation) or driver mutations (in genes involved in proliferation)
Neoplasms emerge from this monoclonal cell population through PROGRESSION: by chance/exposure to more mutations/failure of repair. It is thought neoplasia occurs by accumulation of mutations (~5-7 rate-limiting mutations) until malignant
How do inherited cancers develop?
Germline mutations are inherited, so neoplastic cells get a “head start”
Describe the evidence supporting the monoclonal theory of neoplasia
- study of X-linked dream for glucose 6-phosphate dehydrogenase in tumour tissue from women
- gene has several alleles encoding different isoenzmes
- early in female embryogenesis one allele in each cell is randomly inactivated: LYONISATION
- in heterozygous women that happen to have one allele encoding a heat-stable isoenzyme and one a heat-labile isoenzyme, normal tissues will be a patchwork of both
- neoplastic tissues only express 1 isoenzyme indicating a monoclonal group of cells
- heat stable will work heated, heat labile will not. Apply colour to see which allele was inactivated
General rule for neoplasm naming
Benign: end in -oma
Malignant: end in -carcinoma (epithelial) or -sarcoma (stromal)
Carcinomas are in situ if have not invaded basement membrane, or invasive if penetrated through basement membrane
Blastomas: mainly in children, formed from immature precursor cells e.g. nephroblastoma
Describe the nomenclature for epithelial neoplasms
Benign
- stratified squamous=SQUAMOUS PAPILLOMA (finger-like projections. E.g. skin, buccal mucosa)
- transitional: TRANSITIONAL CELL PAPILLOMA e.g. bladder mucosa
- glandular: ADENOMA e.g. adenomatous polyp of colon
Malignant: carcinoma. (carcinoma not all cancer, but 90%)
- strat sq= SQUAMOUS CELL CARCINOMA (e.g. skin, larynx, oesophagus, lung)
- transitional=TRANSITIONAL CELL CARCINOMA (bladder, ureter)
- glandular=ADENOCARCINOMA (stomach, colon, lung, prostate, breast, pancreas, oesophagus)
- other: BASAL CELL CARCINOMA (skin), MALIGNANT MELANOMA (in melanocytes)
Nomenclature of connective tissue neoplasms
Benign:
- smooth muscle: leiomyoma
- fibrous tissue: fibroma
- bone: osteoma
- cartilage: chondroma
- fat: lipoma (most common benign tumour, foud in all tissue planes, rarely becomes a liposarcoma)
- nerve: neuroma
- nerve sheath: neurofibroma
- glial cells: glioma
Malignant:
- smooth muscle: leiomyosarcoma
- fibrous tissue: fibrosarcoma
- bone: osteosarcoma
- cartilage: chondrosarcoma
- fat: liposarcoma
- glial cells: malignant glioma
Nomenclature of lymphoid/haematopoietic neoplasms
All malignant
Lympoid: lymphoma. Occurs in lymphoid tissue (usually lymph nodes). Hodgkin’s and non-Hodgkin’s types
Haematopoietic: leukaemia “liquid neoplasm”. Starts in bone marrow then abnormal cells enter blood. Acute or chronic, myeloid or lymphocytic
Germ cell neoplasm nomenclature
> 1 neoplastic cell type from >1 germ cell layer
Benign: benign teratoma (dermoid cyst) in ovary. Can contain hair, teeth, thyroid tissue, connective tissue, fat, muscle
Malignant: malignant teratoma (testes), seminoma (testicular slow-growing cancer, usually painless lump)
Neuroendocrine tumour nomenclature
Arise from cells distributed throughout the body. Terminology still evolving
Includes:
-carcinoid tumour (usually in GI tract and lung)
-pheochromocytoma (adrenal)
-small cell carcinoma of bronchus
What does scirrhous mean?
Hard or indurated tumour, due to abundance of connective tissue and collagen
What is a polyp?
An abnormal growth of tissue projecting from a mucous membrane with a stalk
What is rhabdomyosarcoma/rhabdomyoma?
Malignant/benign tumour of striated muscle
Haemangioma
Benign tumour of blood vessels
Angiosarcoma
Cancer of inner lining of blood vessels
Can occur in any area, but usually skin of scalp and face
Can present as skin infection or a non-healing lesion or a soft lump
Mesothelioma
Cancer of mesothelium: the vessels and surface coverings
Meningioma
Benign tumour of brain coverings
What is a naevus?
Benign tumour of melanocytes
Myeloma
Cancer of the bone marrow plasma cells
Incurable
Often have bone disease, anaemia, recurrent infection, hypercalcaemia
Hamartoma
A benign vascular tumour that resembles a neoplasm but results from faulty development in an organ
Choriocarcinoma
Cancer of the placental epithelium
Astrocytoma
Cancer of astrocytes
Type of glioma
Colorectal carcinoma
Cancerous growth of colon, rectum and appendix
Usually adenocarcinomas
Symptoms include rectal bleeding, palpable mass, change in bowel habit
Uterine leiomyoma
Benign tumours of the uterus due to overgrowth of smooth muscle. May grow very big and cause infertility. Oestrogen-dependent
Common name-fibroids
Bundles of spindle cells with blunt-ended nuclei. May cause severe pain if large causing ischaemia, or some fibroids can twist and impair blood flow
Osteosarcoma
Bone cancer
Especially happens at metaphysis, and around the knee and proximal humerus
Primary most common cancer in teenagers, adults usually have it as a secondary metastatic site
Mature cystic teratoma of ovary
Benign tumour of totipotent cells in ovary
Also called dermoid cyst
Almost-always lined by skin-like structures
Struma ovarii
Rare teratoma of usually ovaries but can be in other areas, with mostly thyroid tissue composition–>can cause hyperthyroidism
Usually benign but can be malignant
Chronic lymphocytic leukaemia
Cancer of mature lymphocytes
Usually insiduous onset, more likely to affect adults
