Oncology Flashcards
What are the mechanisms of oncogene activation?
Chromosomal translocation, gene amplification, point mutations, viral insertions.
What are oncogenes?
Mutations that produce oncogenes with dominant gain of function. Retroviral sequences that are responsible for transforming properties are called viral oncogenes. They have cellular homologues called cellular oncogenes. Proto oncogene is used to describe cellular oncogenes that do not have transforming potential to form tumours in their native state but can be altered to lead to malignancy.
What are tumour suppressor genes?
Tumour formation can result from a loss of inhibitory functions associated with another class of cellular genes called the tumour suppressor genes.
What are the seven alterations that the vast array of cancer genotypes are a manifestation of?
These characteristics are acquired during the process of carcinogenesis and can be considered as: a self sufficiency in growth, an insensitivity to anti growth signals, an ability to evade programmed cell death, limitless replicative potential, an ability to sustain angiogenesis, an ability to invade and metastasise, an ability to evade host immunity.
What is the grade of a tumour?
The grade of a tumour refers to a pathological description of the tumour and is based upon several criteria. (e.g mitotic rate, tissue architecture and pleomorphism.) This should not be confused with stage, which refers to the clinical extent of the disease.
What is staging of a tumour?
Involves a consideration of primary tumour size, presence or absence of local lymph node involvement and presence or absence of distant metastases. To stage solitary tumours we use the TNM system. T= primary tumour, N=regional lymph node, M=metastases.
Describe Evaluating the primary tumour (T) in the TNM staging process
Physical examination - size of the tumour, mobility with respect to underlying tissues and degree of fixation, presence/absence and degree of erythema, presence/absence of ulceration, relationship with associated anatomical structures. Diagnostic imaging - required for deep tumours, tumours involving vital structures, bone, tumours adjacent to bone. Endoscopy or bronchoscopy in cases of suspected tumours of the GI tract, respiratory tract or urogenital system, Biopsy. The primary tumour is allocated a numerical or alphabetical suffix denoting size and extent of the tumour.
Describe lymph node evaluation in the TNM system
Physical examination - size of the lymph node, mobility with respect to underlying tissues and degree of fixation, texture and consistency, presence/absence of ulceration, relationship with associated anatomical structures. Diagnostic imaging - required for deep lymph nodes that cannot be physically examined. Aspirate or biopsy. The lymph node is allocated a numerical value depending on the presence or absence of neoplastic disease.
Describe how metastatic disease (M) is evaluated in the TNM staging system
Physical examination/history - this may give essential clues to the possibility of metastasis including weight loss, coughing or lameness. Diagnostic imaging - will depend on the tumour type and its natural biological behaviour. Particular attention should be paid to lungs, liver and bones. Biopsy - may be required too confirm metastatic disease versus nodular hyperplasia. The patient is allocated an M value depending on the presence / absence of disease at distant sites.
Describe staging for disseminated or multicentric disease
Diseases such as lymphoproliferative disorders often present as a disseminated form and thus the TNM classification is not appropriate. For diseases such as lymphoma the disease may be staged according to the various organ systems involved and assigned a numerical figure.
What is post surgical biopsy essential for?
to ensure surgical margins were adequate, the histological type and the grade of the tumour, that no follow up therapy is required, to inform prognosis.
What does biopsy have the potential to inform?
The detection of neoplastic disease in either primary or secondary sites, the tumour type, the grade of the tumour, the adequacy of surgical excision.
When deciding on an appropriate technique what must the clinician consider?
The amount of tissue that should be recovered in the biopsy, the position within the tumour that tissue is to be recovered from, the type of tissue to be biopsied, the anatomic location of the tumour.
What is cytology?
The examination of individual cells or small groups of cells which have been recovered from tumour masses or from neoplastic effusions.It is used to identify the presence of neoplastic diseases. The cells in cytological preparations often bear no relationship to their original arrangement within the tumour or to its architecture. Specimens can b e recovered with little disruption of the tumour and the surrounding tissues.
What is needle biopsy?
Used to remove small cores of tumour tissue from solid lesions. Used when it is important to recover sufficient tissue to establish tumour type. eg recovery of tissue from tumours of internal organs without surgical procedures, recovery of tissues from bone lesions.
What is a skin punch biopsy?
Excellent for skin and superficial soft tissue tumours. Recover substantially more tissue than needle aspirates. Recovered tissue retains much of its architecture and is suitable for routine processing techniques.
What is an incisional biopsy?
Surgical removal of a solid piece of tissue from a tumour for histopathological examination. It is used where a substantial amount of tumour tissue is required to enable histopathological typing and grading. Incisional biopsy provides an opportunity for exposure of the biopsy site allowing accurate selection of the site for tumour sampling and reducing the risks of post biopsy complications. Normally requires general anaesthesia.
What is Excisional biopsy?
the complete surgical extirpation of a tumour following which tissue samples are removed for histopathological examination, which should ideally be performed on all excised specimens.
Describe a bone marrow biopsy
Often indicated in the diagnosis of conditions affecting the lymphoid and myeloid systems. The biopsy may take the form of an aspirate or a core biopsy. Indications for bone marrow biopsy: non regenerative anaemia of undetermined cause, investigation for secondary immune mediated haemolytic anaemia, staging and or diagnosis of haematopoietic tumours. One can use the humerus, femur or the iliac crest. A bone marrow needle is used.
What is a bone marrow core sample?
A bone marrow biopsy is carried out, but after the aspirate has been retrieved the needle is advanced to obtain a core sample. The needle is rocked forward and backward after advancement to saver the bone in the needle from its base. When the needle is removed, a smaller wire obturator is used to retrograde the biopsy material out of the top of the needle.
What are paraneoplastic syndromes?
They are diverse clinical syndromes resulting rom systemic effects of neoplasia. The effects occur at sites distant from the tumour and can affect many end -target organs. Syndromes include hormonal, metabolic, haematologic, neuromuscular, dermatologic, musculoskeletal, renal, gastrointestinal and cardiovascular disorders. PNS may occur as a result of immune-mediated mechanisms, peptide protein or hormone secretion, cytokine secretion, production of enzymes or other biochemical mechanisms that interfere with normal metabolic pathways.
