Neoplasia Lecture 2

Neoplasia Lecture 2

• Neoplasia is the abnormal growth of cells.
• Differentiation refers to how similar a tumour is to its cell of origin, both morphologically and functionally.
• Anaplasia is the lack of differentiation, an indicator of malignancy.
• Benign tumours are composed of well-differentiated cells resembling normal cells.
• Benign tumours often grow slowly as cohesive masses.
• Benign tumours usually remain localized and have a capsule.
• Examples of benign tumours include lipomas (fat) and chondromas (cartilage).
• Well-differentiated benign tumours have rare mitoses (cell divisions).
• Malignant tumours exhibit various degrees of differentiation from well to poorly differentiated and anaplastic.
• Malignant tumours often exhibit a wide range of parenchymal cell differentiation and morphologic alterations.
• Malignant tumours can display nuclear pleomorphism (variation in size and shape).
• Nuclear abnormalities such as extreme hyperchromatism, variation in size and shape, and prominent nucleoli may be present in malignant cells.
• A higher nuclear-to-cytoplasmic ratio is often observed in malignant cells.
• Increased mitotic activity (cell division) is a feature of malignancy.
• Atypical mitoses (tripolar or quadripolar) are often seen in malignant cells.
• Tumor giant cells are characteristic of malignant tumours.
• Loss of polarity of tumor cells is characteristic of malignant tumours.
• Alteration or loss of functional capacity (paraneoplastic syndrome) can occur with malignancies.
• Examples of well-differentiated squamous cell carcinoma and anaplasia and abnormal mitosis are illustrated.
• Dysplasia is characterized by a loss in the uniformity of cells and in their architectural cells, but not synonymous with cancer.
• Mild or moderate dysplasia may regress if inciting causes are removed
• Severe dysplasia involving the entire epithelium is referred to as carcinoma in situ (preinvasive stage of cancer).
• Local invasion is a hallmark of malignancy, indicated by progressive infiltration, invasion, and destruction of adjacent tissues.
• Benign tumours, on the other hand, grow as cohesive expansile masses that remain localized, often with a capsule (a rim of compressed fibrous tissue).
• Metastasis is the spread of a tumour to sites physically separate from the primary tumour; it is a hallmark of malignancy.
• Approximately 30% of newly diagnosed solid tumours (excluding melanomas) show clinically evident metastases.
• 20% of newly diagnosed solid tumours (excluding melanomas) have occult (hidden) metastases.
• Metastatic spread is more common in larger and more anaplastic tumours.
• Very small cancers can still spread, while very large, but well differentiated cancers may not.
• Basal cell carcinomas and most CNS cancers are highly locally invasive but rarely metastasize.
• Leukemias and lymphomas are usually considered disseminated and malignant at diagnosis.
• Pathways for metastasis include seeding within body cavities, lymphatic spread, and hematogenous spread (through blood vessels).
• Seeding involves the spread by the dissemination of malignant cells into a natural body cavity, often seen in cancers of the ovary.
• CNS cancers, and more specifically ependymomas and medulloblastomas may spread via the cerebrospinal fluid (CSF) seeding along the meninges, to the brain and or spinal cord.
• Lymphatic spread is more common in carcinomas, while hematogenous spread is favored by sarcomas.
• Cancers originating near the vertebral column can often disseminate through the paravertebral venous plexus.
• Hepatocellular carcinomas and renal cell carcinomas readily spread through the venous system.
• The pattern of lymph node involvement in cancer depends on the site of the primary tumour and the natural pathways of lymphatic drainage.
• A sentinel lymph node is the first lymph node receiving lymph flow from a primary tumour.
• Hematogenous spread, favoring sarcomas, is when malignant cells enter the blood vessels and spread to other organs, where they form secondary tumours.
• Common secondary sites include the lungs and the liver (receiving metastatic deposits from organs with portal venous drainage).

This quiz covers key concepts from Neoplasia Lecture 2, focusing on the differences between benign and malignant tumors. Learn about cell differentiation, anaplasia, and the characteristics of various tumor types. Test your understanding of neoplasia and its implications in pathology.