Test 2- Neoplasia Flashcards
Neoplasia
The process of tumor formation.
Neoplasia becomes more common as age increases.
Neoplasm or tumor
“New growth” - “composed of cells originally derived from normal tissues that have undergone heritable genetic changes that allows them to become relatively unresponsive to normal growth controls and expand beyond their normal anatomic boundary”
Oncology
Study of tumors or neoplasms.
Neoplasm (tumor): two basic components
- Parenchyma- formed by the neoplasic cells that ma
- Stroma (connective tissue and blood vessels that support the neoplastic cells). Some tumors induce prominent desmoplasia (the formation and development of collagen-rich fibrous connective tissue stroma): e.g.: scirrhous carcinomas (“stony hard consistency”)
Supplies the nurishment for the neoplasa cells
Pre-neoplastic changes
“Because cell replication
is involved in neoplastic transformation, regenerative, hyperplastic and dysplastic proliferations are fertile soil for carcinogenesis to occur”…
- this can be any process that is involved in cell replication
hyperplasia can be a pre- neoplasic change BUT it doesn’t mean that everytime there is hyperplasia that there is a tumor
Papillary ductal hyperplasia,
breast
The image above shows a small lesion , under 1 mm, with severe cytologic atypia, apocrine features and no necrosis. Because the architecture is disorganized, lesions such as these may be classified as “carcinoma in situ”
- epithelial tumors
Hyperplasia
Metaplasia
Reversible change in which one adult cell type is replaced by another adult cell type of the same germ cell line. Usually specialized epithelium is replaced by less specialized epithelium.
Metaplasia is often, but not always an adaptive response.
Epithelial metaplasia is commonly to squamous epithelium and usually due to chronic irritation (not alwayse.g.: Vitamin A deficiency).
In the respiratory epithelium squamous metaplasia leads to impaired function of the mucociliary escalator (picture)chronic heavy cigarette smokers (10-fold greater risk to develop lung cancer in comparison to non-smokers)
Carcinoma in situ. The entire thickness of the epithelium is replaced by dysplastic cells. There is preservation of the basement membrane but no orderly differentiation of squamous cells.
Mesenchymal Tumors:
COMMON TYPE OF TUMOR
Mesenchymal Tumors: Arise from cells of mesodermal origin.
– Benign:suffix“oma”
– Malignant:Suffix“sarcoma”
Epithelial Tumors:
COMMON TYPE OF TUMOR
Epithelial Tumors: Primarily arise from cells of endodermal and ectodermal origin. Benign: papilloma exophytic growth from an epithelial surface; polyp benign epithelial tumor that projects from a mucosal surface.
– _Malignant:_carcinoma;addorganoforigin;addwhetherarisesfrom glandular epithelium or form glandular structures microscopically; add whether induces desmoplasia (scirrhous) or produces mucin (mucinus).
– Carcinoma in situ
Mixed Tumors
Mixed Tumors (multiple cell types derived from a single or multiple germ cell layers – pluripotential or totipotential cell)
– Mixed mammary tumors in dogs
– Teratomas
– Nephroblastoma(Embryonalnephroma,Wilms’tumor)
Teratomas
“Arise from totipotent germ cells. They contain tissues derived from all embryonic cell layers and consist of a bizarre mixture of adult and embryonic tissue types
pic Horse, testicular teratoma
Nephroblastoma, pig
Nephroblastomas are Also known as embryonic Nephromas or Wilms’ tumors
Tissue of origin: metanephric blastema
Epithelial and mesenchymal components- Mixed Tumors
Nephroblastoma, dog
Tissue of origin: metanephric blastema
Epithelial and mesenchymal components
Nephroblastomas are Also known as embryonic Nephromas or Wilms’ tumors
There is a unique tumor reported in thoracolumbar junction of the spinal cord of young dogs(up to 3 years old), mainly German Shepherds, that is now believed to be a nephroblastoma.
Nephroblastoma, pig
Biology of tumor growth: Benign versus Malignant
a) Differentiation/ anaplasia
— benign tumors- are very well differentated and they will very closely resemble the cell of the origin
neoplasic cells- look different from the cells of origin
b) Rate of growth
malignant tumors grow extremely fast, but benign tumors grow at a more normal rate
c) Local invasion (expansile/ infiltrative growth)
malignant tumors-infiltrative growth—- they are invasive
d) Presence or absence of metastasis(secondary growths of a tumor)
Differentiation/ Anaplasia
Refers to the extend to which parenchymal cells resemble the correspondent normal parenchymal cells, both morphologically & functionally
Benign tumors are well-differentiated
Malignant neoplasms can be well-differentiated or undifferentiated (the latter are said to be “anaplastic”).
Anaplasia is characterized by
Anaplasia (“cellular atypia”) is characterized by:
—-Pleomorphism- tumor cells have different sizes, the nuclei are different sizes and morphology
—-Abnormal nuclear morphology
—High mitotic rate
—Loss of polarity (disorganization)
Anaplasia is also understood as lack of
Anaplasia is also understood as lack of differentiation“to form backwards”, implying a reversal of differentiation to a more primitive level.
anaplastic cells arise from
The truth is that in most cancers anaplasia does not represent reverse differentiation of mature normal cells; anaplastic cells arise from less differentiated stem cell-like (totipotent cells) present in tissues.
Anaplasia: pleomorphic muscle cells: Rhabdomyosarcoma
maliganant tumor arising from the mesechemyal cells
skeletal muscle
high degree of anaplasia
In general, the growth rate of tumors correlates with
In general, the growth rate of tumors correlates with their level of differentiation, and thus most malignant tumors grow more rapidly than do benign lesions” (Robbins & Cotran)there are of course many exceptions to the rule…
b) Rate of Growth/ cell proliferation
The main mechanisms that regulate tissue growth are:
- Rate of cell proliferation (fraction of cells in the replicative pool adds to cells undergoing mitotic activity)
- Rate of programed cell death (apoptosis)
This is also applicable to neoplasms…
Apoptosis
Non-lethal genetic damage lies at the heart of carcinogenesis.
Genetic damage per se does not constitute mutation, mutation occurs during DNA replication”the alteration in DNA sequence caused by genetic damage needs to be imprinted in the genome.