Pathology: Neoplasia Flashcards
Mixed tumors
Tumors that are monoclonal develop into widely varying cell types (i.e. teeth and hair). Pleomorphic.
Teratomas
Tumors that contain tissue from more than one germ cell layer. These often come from totipotent cells
Benign tumor differentiation
Neoplastic cells are well-differentiated and closely resemble the surrounding parenchyma
Why are malignant tumors more difficult to diagnose pathologically than benign tumors?
Malignant neoplastic cells vary greatly in differentiation and anaplasia.
Hallmarks of malignancy
Anaplastic neoplasms, hyperchromatic nucleus, mitoses (abnormal cell divisions), loss of polarity, ischemic necrosis and giant cells.
*What do you see?
Benign, well differentiated tumor in the uterus
*What do you see?
Anaplastic tumor. Note pleomorphism, hyperchromatic nuclei and giant tumor cells
*What do you see?
Anaplastic tumor. Note abnormal tripolar spindle in center cell.
What often occurs in metaplastic epithelial tissue?
Dysplasia = loss of uniformity of individual cell and architecture
When is a carcinoma considered to be invasive?
Once it breaches the basement membrane. Before that, it is an in situ carcinoma
What clinical aspect of neoplasia makes detection difficult?
By the time you find a solid tumor most of its cells are no longer in the replicative pool.
What determines the rate at which a tumor grows?
Doubling time, growth fraction (number of cells in replicative pool) and rate of cell death
Where do most tumor cells go when they leave the replicative pool?
G0 phase
What ultimately determines how fast a tumor grows.
Cell production and cell loss ratio
Why does radiation or surgery normally precede chemotherapy?
Chemotherapy drugs are effective against drugs in the cell cycle. Since many cells in the tumor are in G0, radiation and surgery debulk the tumor to try and get the cells back into replication phase.
What physiological factors can increase or decrease tumor growth over time?
Hormonal stimulation or blood supply
Why are malignant stem cells generally non responsive to current therapies?
Stem cells have a low level of cell division and express drug resistant factors.
*What do you see?
Benign breast tumor. Note connective tissue border that prevents to tumor from spreading into surrounding tissues.
*What do you see?
Malignant breast tumor. Note invasion of breast stroma, absence of capsule, fat in nests and cords of tumor cells
What are the two most reliable features that differentiate a malignant tumor from a benign tumor?
- Metastasis 2. Invasiveness
What malignant tumors do not usually metastasize?
Gliomas (glial cells in the CNS)
What three ways does cancer normally spread?
Seeding, lymphatic spread and hematogenous spread.
Where does seeding most often occur?
Peritoneal cavity
What is the most common mode of cancer spread?
Lymphatics
What lymphatics are most likely to be affected when cancer spreads?
Lymph node closest to the primary site of neoplasia
A patient experiences swollen lymph nodes and a lump on her breast. What do you suspect regarding tumor metastasis?
Possible metastasis due to migration to lymph node. Possible cancer arrest within the lymph node.
What organs are most often affected by cancers that migrate hematogenously?
Liver and lungs. Cancer gets into veins easier because they are thinner and most veins go through the liver and lungs.
*What do you see?
Metastatic nodule from pancreas in the liver
Genetic factors that may predispose someone to cancer
Autosomal dominant: stay in a particular place w/particular phenotype, Defective DNA-repair, Familial cancers: combination of multiple low-penetrance alleles
Why would physicians prescribe COX-2 inhibitor to a colon cancer patient?
Chronic inflammation and its mediators are linked to development of cancer.
What are the four classes of regulatory genes in neoplasia?
Proto-oncogenes, tumor suppressor genes, apoptosis genes, and DNA-repair genes.
7 Cellular Physiological Changes That Determine Malignancy
Proliferation w/o external stimuli, Nonresponsive to strong inhibitory stimuli, Inactivation of apoptotic genes (p53), Limitless replicative potential, Angiogenesis, Ability to invade and metastasize, and DNA repair defects
How do growth factors contribute to development of neoplasms?
They activate receptors that activate, most often, a portion of the signal pathway that fell prey to oncogenes. That portion greatly amplifies the signal transduction and proliferation of the cell.
What receptors are particularly susceptible to oncogene mutations?
Tyrosine kinase receptors. They phosphorylate each other and can remain in an activating state without any stimulus.
Why might growth factor receptors be good targets for targeted cancer therapy?
Growth factor related cancers usually have a receptor mutation. Targeting receptors is fairly easy compared to other methods.
Most common abnormality of proto-oncogenes in human tumors?
Point mutations in RAS or its GEF, which activates the MAP kinase pathway which signals for cell proliferation.
What gene influences receptor kinase mutations that are not growth factor related?
Translocation of ABL gene from chromosome 9 to chromosome 22. JAK2 activation and STAT induces proliferation.
This transcription factor is thought to play a role in cancer by activating more origins than needed during DNA replication.
MYC
What cyclins are most commonly mutated in patients with tumors?
Why would a mutation in p21, p27, or p57 put someone at a high risk for cancer?
They inhibit CDKs widely and mutations would activate CDKs and the cell cycle widely.
What phase of the cell cycle prevents replication of cells with DNA defects?
G1/S checkpoint. Induces apoptotic pathways if the DNA is not repaired.
Defects at which part of the cell cycle give chromosomal abnormalities?
G2/M checkpoint. If DNA does not replicate properly and chromatids cannot separate properly, cells are arrested in G2.
What sensors and transducers are used at the cell cycle checkpoints?
Sensors: RAD family and ATM. Transducers: CHK kinases
What effector molecules regulate at the G1/S checkpoint?
p53 induces cell cycle inhibitor p21
What effector molecules regulate at the G2/M checkpoint?
p53 and other mechanisms