Lecture 3 2/6/25 Flashcards
What is a benign tumor?
tumor that does not invade surrounding tissue or metastasize
What is a malignant tumor?
neoplasm that is locally invasive or metastatic
What are the components of a morphologic diagnosis for a neoplasm?
-tissue
-tumor type
Which component of a morphologic diagnosis is added for metastatic neoplasms?
indicating that the tumor is metastatic in the tissue it is now found in
What is a grade?
assessment of clinical behavior of malignant neoplasms based on their microscopic appearance
What is a stage?
indication of the extent of tumor growth and spread throughout the body
What are the characteristics of grading?
-histologic diagnosis
-links microscopic features with clinical aggressiveness
-includes degree of differentiation, number of mitoses, and architectural features
What are the characteristics of staging?
-clinical diagnosis
-conveys extent of neoplasia in the patient
-includes tumor size, degree of local invasion, lymph node involvement, and presence of distant metastases
What components can be included in tumor grading?
-mitotic count
-amount of necrosis
-degree of differentiation
-nuclear pleomorphism
-cellular pleomorphism
Which neoplasms have well-established grading schemes?
-canine soft tissue sarcomas
-canine cutaneous mast cell tumors
-canine lymphoma
-canine mammary carcinomas
-feline mammary carcinomas
What are the components of grading for canine soft tissue sarcomas?
-mitotic score
-tumor necrosis score
-tumor cell differentiation score
How does tumor grade correlate with prognosis?
-low grading has the best prognosis
-intermediate falls between low and high grading
-high grading has the poorest prognosis
What are the characteristics of canine mast cell tumors?
-most frequently diagnosed malignant cutaneous neoplasm in dogs
-variable gross appearance
-can be cutaneous or subcutaneous
-eosinophils are almost always within the neoplasm
What are the components of grading for canine mast cell tumors?
-mitotic count
-multinucleated cells
-bizarre nuclei
-karyomegaly
What are the grading classifications for canine mast cell tumors and why?
-low and high grade
-previous system of low, intermediate, and high resulted in nearly every neoplasm being intermediate, making prognosis difficult to determine
What is the basis for grading of lymphoma?
histologic tumor features in the lymph nodes
What is the grade of lymphoma based on?
mitotic count
How is the size of lymphoma (such as small cell vs. large cell) determined?
based on nuclear size in comparison to an RBC
What are the further classifications used for lymphomas?
-immunophenotype
-pattern (nodular vs diffuse)
-clinical behavior
-location
What are the components of grading for canine oral/lip melanocytic neoplasms?
-nuclear atypia
-mitotic count
-Ki-67 index
-bone invasion
What are the components of grading for canine cutaneous melanocytic neoplasms not at the oral cavity or lip?
-nuclear atypia
-mitotic count
-Ki-67 index
-presence of ulceration
-tumor thickness
-extension beyond the dermis
What can result in a biopsy not being diagnostic?
-too small of a sample
-crush artifact
-cautery artifact
-poor fixation
-anaplastic neoplasm
What is an anaplastic neoplasm?
tumor in which cells do not resemble any normal cell type and for which the tissue of origin cannot be determined; cells are too poorly differentiated
What are the characteristics of immunohistochemistry?
-application of antibodies to tissue sections that bind to specific antigens
-antibody binding is detected by chromogen-associated color change
-can be performed on formalin-fixed and paraffin-embedded tissues
What is immunocytochemistry?
similar technology to immunohistochemistry, except performed on cytology samples such as aspirates or impression smears
What are the benefits of immunohistochemistry?
-identification of poorly differentiated neoplasms
-identification of more specific neoplastic phenotype
-useful for prognosis and/or making treatment decisions
What are the characteristics of PCR for Antigen Receptor Rearrangements (PARR)?
-assesses clonality
-useful to differentiate neoplastic from inflammatory lymphocytes
What are the characteristics of flow cytometry?
-counts cells and identifies them by surface markers
-must be done on fresh tissue or live cells; not formalin-fixed tissue
What are the characteristics of metastasis?
-when a malignant tumor spreads to another site within the same organ or in a different organ
-most definitive indicator of a malignancy
-responsible for many neoplasia-related euthanasias and deaths
What are the pathways of spread for neoplasms?
-lymphatic vessels (carcinomas)
-blood vessels (carcinomas and sarcomas)
-direct seeding (carcinomatosis and sarcomatosis)
Which cancer types are most likely to undergo carcinomatosis?
-ovarian
-pancreatic
-biliary
-intestinal
Which tumors are transmissible?
-canine transmissible venereal tumor
-devil facial tumor disease
-bivalve transmissible neoplasia
