13: Benign v Malignant

What type of mutations result in malignant tumors

Non-lethal heritable mutations

How do benign tumors cause damage

Compress surrounding tissues and may restrict blood flow, causing atrophy

How do malignant tumors cause damage

Infiltrate nearby tissues, may metastasize

Pleiomorphism

Change in size and shape of cells and nuclei

Histo characteristics of an abnormal nuclei

• Hyperchromic due to excessive genetic material

• Large nuclei

• Prominent nucleoli

Significance of mitotic figures

Indicates that there is increased mitotic activity

Characteristics of a tumor giant cell

Large cell with multiple nuclei

Significance of cellulular polarity

Crucial for epithelial and secretory cells, the loss of polarity may mean they don’t function correctly

Microscopic characteristics of benign neoplastic cells

• Well differentiated

• Uniform

• Normal nuclei and nucleoli

What structure is common in benign neoplasms that helps separate them from normal tissue

Capsule

Gross characteristics of malignant neoplasms

• Initially slow growing

• Aggressive growth

• Infiltrative

• No respect for boundaries

What encourages the switch from slow growth to aggressive growth in malignant neoplasms

The immune system will kill all the cells it can, inadvertently selecting for the cells that adapt to survive, resulting in a neoplastic cell population of aggressive subclones

What characteristic always means that a tumor is malignant

Metastasis

Why are malignant tumors less mobile

Not self contained, often very infiltrative

What substance/structure is part of tumors and supports their growth

Stroma

Why are excisional margins so important for malignant tumors

You may not know how far they have infiltrated, and if any of it is left it will lead to recurrence

Cause of central necrosis in tumors

Low nutrients to the center → hypoxia → death → central depressions in tumors

Cytology

Looking at cells

Biopsy/Histopath

Looking at whole tissues

What is described by tumor grading

How bad is the type of tumor

Who grades tumors

Pathologists

What is descried by tumor staging

How far along is the tumor

Who stages tumors

Clinicians

How is a diagnostic cytology sample collected

Fine needle aspirates

Purpose of a diagnostic cytology

• Initial determination of tumor type

• May allow determination of benign v malignant

• Complements biopsy

Types of biopsy

• Incisional

• Excisional

Incisional biopsy procedure and purpose

Removal of a partial sample of the mass, often done if the tumor is in an unfortunate location to help plan possible treatments

Excisional biopsy procedure and purpose

Complete removal of a mass, done to cure or reduce the tumor burden

Default histopath stain

H & E

Why might special histopath stains be used

To highlight certain characteristics or pathogens

What types of stains are commonly used to diagnose lymphoma

Immunohistochemical stains

Lymphoma characteristics determined by additional testing

• T or B cell

• Chronic or acute

• Monoclonal or polyclonal

Additional testing done for determining mast cell prognosis

Testing for tumor proliferation markers

Why might an excisional biopsy be “painted” with different stains

To visualize if there are any neoplastic cells approaching the margins

Characteristics used to stage a tumor

• T: primary tumor size

• N: involvement of lymph nodes

• M: metastasis to other organ systems

Characteristics used to grade a tumor

Morphologic features that are associated with prognosis

• Differentiation

• Invasiveness

• Cellularity

• Mitotic index