Benign and malignant tumors Flashcards
What is a neoplasm?
- “New growth”, Abnormal mass of tissue, exceeding and uncoordinated with the normal growth, which persists even after the cessation of the original stimuli
What is meant by dysplasia?
It is the abnormal growth of cells within tissue losing their original uniformity and architectural orientation, can predispose to cancer
What are the types of neoplastic proliferation?
1) Benign: Localized and non-invasive & slow-growing
2) Malignant “cancer”: spreads and invasive
What causes cancer?
It is a genetic disorder due to the mutations of DNA, which are either acquired spontaneously or induced by the environment
What are the hallmarks of cancer?
- Occurs due to the accumulation of mutations
1) Evades growth suppressors (Tumor suppressor genes)
2) Activates invasive and metastasis growth
3) Enables replicative immortality
4) Induces angiogenesis
5) Resists cell death (apoptosis)
6) Sustains proliferating signals
What is the nomenclature of neoplastic cells?
1) Parenchyma: The proliferating cells
2) Stroma: The connective tissue & blood vessels that support it
What is the specific nomenclature of benign tumors?
- We find the suffix -oma to all benign tumors + cell type where tumor arises
- Some are classified by their microscopic or macroscopic appearance (adenoma for gland-shaped microscopic morphology “Tubular adenoma, colon”, papilloma = papillary-like projections “epithelial neoplasm” produces finger-like fronds, etc)
- Others are classified by their cells of origin (lipoma, fibroma, myoma, chondroma)
- Exceptions: melanoma and lymphoma are malignant, (they were named before nomenclature was introduced)
What is a polyp?
- Mainly associated with adenoma, it is a Mass projection over a mucosal surface (gut), a macroscopic, can also be due to inflammation
What is a hamartoma?
A mass of disorganized tissue, inside the particular site (cartilage tissue in lungs) and during embryogenesis where some mass-like structures are present in a disorganized way
What is a choristoma?
A congenital anomaly of heterotopic cells (normal cells in the wrong location), like pancreatic cells in the liver/GIT
What is a teratoma?
- Special type of mixed tumors, containing recognizable mature/immature or tissues
- Represents more than one germ layer (originating from totipotential cells)
For example, in the teratoma neoplasm of the ovary, you can find teeth
What is the nomenclature of malignant tumors?
They could be (differentiated based on the cell origin):
1) Sarcomas “mesenchymal tumors”: (connective tissue that gives rise to various cell types, including bone cells, cartilage cells, and muscle cells)
- Chondrosarcoma: cartilaginous tumor
- Fibrosarcoma: fibrous tumor
- Osteosarcoma: bone tumor
2) Carcinomas “epithelial tumors”:
- Adenocarcinoma: gland-forming tumor
- Squamous cell carcinoma: squamous differentiation
- Undifferentiated carcinoma: no differentiation
note: carcinomas can arise from ectoderm, mesoderm, or endoderm
What is a sarcoma?
Malignant tumors arising from the mesenchyme (Connective tissue)
What is a carcinoma?
Malignant tumors that originate from the epithelium
What is the difference between the nomenclature of benign and malignant tumors?
In benign we add cell of origin/ or micro/macroscopic appearance + oma
In malignant we add (sarcoma or carcinoma) depending on the cell origin
Lymphoma (a malignant tumor of lymphatic tissue) & melanoma (a malignant tumor of the skin) – do not follow normal nomenclature, and were named before this invention.
What is meant by anaplasia?
Lack of differentiation (which is the resemblance of comparable normal cells both morphologically and functionally)
- With benign being well differentiated and malignant that do not have a poor prognosis
What are the differences between benign and malignant tumors?
1) Benign are well-differentiated and typical of tissue origin, while malignant lacks differentiation and is often atypical
2) Benign Usually progressive and slow; may come to a standstill or regress; mitotic figures are rare and normal, while malignant are slow to rapid mitotically, with numerous and abnormal mitotic figures, the less differentiated they are the faster the growth rate
3) Benign tumors are well-demarcated masses that do not invade nor infiltrate surrounding tissue (they push “forming a capsular structure”), while malignant tumors are invasive, & infiltrate surrounding normal tissue
4) Bening tumors are metastaically inactive, while malignant are highly metastatic, the larger and more undifferentiated they are the more metastatic, and the metastases are regarded as secondary tumors located in remote tissues (discontinuous with the primary tumor)
Benign:
Slow growing, Encapsulated (as they “push”), Expansile growth, No Metastasis, Well Differentiated
Malignant:
Rapidly growing, Non encapsulated, Infiltrative growth, Metastasis,
Well-Poorly differentiated
What is the hallmark of malignant tumors?
Anaplasia, detected by the morphologic patterns
What are the features of malignant cells?
1) Hyperchromatic (abundant DNA) makes the nucleus darker
2) Increases the N:C ratio to 1:1 instead of 1:6
- Chromatic clumping
- Prominent nucleoli
3) Cells vary in size & shape (pleomorphism)
4) Increased, bizarre Mitosis (“Mercedes figure is visible under the microscope”)
5) MALIGNANT CAN BE WELL differentiated-grade 1, MODERATELY differentiated-grade 2, or POORLY grade 3(grows faster)
6) Loss of polarity (Present in a disorganized way, crowded, loose line compared with other cells)
7) Might have tumor giant cells (with a large nucleus “in relation with the cell”, with hyperchromatic nuclei)
What are the steps of Neoplasia?
- Cancer invasion:
1) Cancer cells express cell surface receptors enabling them to bind to the basement membrane component (laminin)
2) Tumor cell disrupts and invades the basement membrane
3) Tumor cells metastasize by way of lymphatics or BV
Explain squamous cell carcinoma
- Occurs mainly in the skin, Oral cavity, Oesophahus, Uterine cervix, etc)
- Risk factors are:
- Sun exposure
- Carcinogens (Tars)
- Chronic ulcers
- Burn scars
- Arsenic poisoning
- Radiation exposure
- A well-differentiated (but malignant as it invades into the dermis) hall-mark of squamous cell carcinoma is the attempt of the invading cell to produce keratin into the nest forming a “pearl” that is viewed under the microscope
- The tumor cell mass invades through the basement membrane dermis
- Can also happen in other tissue where the lining is squamous epithelium (not just skin), or after metaplasia of the lung happens
Why is adenocarcinoma malignant?
Due to its large size, and exophytic (grow outwardly) growth pattern, obstructing the lumen
- Moderately differentiated
- There is still a glandular configuration, but the glands are irregular and crowded
- Many of them have lumens containing bluish mucin.
What is the mechanism by which tumor cells spread?
The epithelial-mesenchymal process (EMT):
1) Detaches themselves via loosening of the intercellular junctions
2) Invade basement membrane and tissues until they reach the Blood Vessels enter it and then extravasate
3) Settels in a new organ start forming BV (angiogenesis) and proliferates
- Lung & prostate cancer can go to the bone
What are the pathways by which tumors spread?
1) Direct pathway
2) Body cavities (peritoneal, pericardial, subarachnoid, pleural)
3) Blood vessels
4) Lymphatic vessels
Which organs are considered a good source for malignancy?
1) Lungs – Systemic Venous blood
2) Liver – GIT venous return, nutrition.
3) Brain – End arteries
4) Bones
What is meant by staging?
The process of determining how much cancer is present in the body (tumor size and spread)
“TNM” system:
1) Tumor size
2) Lymph node status
3) Metastasis
What is meant by grading?
1) The cytological differentiation of tumor cells
2) Number of mitosis within the tumor
- High grade – poorly differentiated – more aggressive than well-differentiated
As grades increase the severity increases.
