21. Neoplasia: Classification of Tumors

What are the four broad categories of tumors?

E
M
N
O

• epithelial cells

• mesenchymal cells

• neural crest cells

• other

What give rise to epithelial tissues and tumors?

all three embryonic layers (ectoderm, mesoderm, and endoderm)

What do epithelial cells have? What is their function?

cell to cell junctions; line surfaces (epidermis, mucosa), form glands, cords, or tubules

How are epithelial tumors typically described grossly?

off white and firm

What are examples of benign epithelial neoplasms?

A
P
P

• adenoma

• papilloma

• polyp

benign epithelial tumor with glandular or tubular differentiation

adenoma

benign exophytic (growing outwards) tumor that is typically arising from a cutaneous or mucocutaneous surface

papilloma

What are examples of malignant epithelial neoplasms?

A
C

• adenocarcinoma

• carcinoma

What is this showing?

epithelial tumor (squamous papilloma)

What is this showing?

equine squamous cell carcinoma

benign epithelial tumors projecting from a mucosal surface

polyp

What is this showing?

intestinal polyp

What is this showing?

endometrial polyp

What are malignant tumors of epithelial origin referred to as?

carcinomas

What patterns can carcinomas form? What are these based on?

N
C
T
S
T

• nesis

• cords

• trabeculae

• solid

• tubular

cell of origin the tumor originates from

When the tumor is glandular in nature, what is it referred to as?

adenocarcinoma

Typically, carcinomas have ________ well-defined borders, are ________-________, can be ________-________ or have a ________ surface, and are ________ in texture.

less; off-white; multi-lobulated; corrugated; firm

What is this showing?

adenocarcinoma

What tumor type tends to produce a schirrous or desmoplastic response better than most?

carcinomas

What is this showing?

schirrous or desmoplastic response

derived from the mesoderm embryologically and are an incredibly diverse category of cells that can develop into tumors

mesenchymal tumors

Typically, mesenchymal tumors are tumors of ________ cells from tissues. They can be anything from adipocytes to cells forming bone to muscle cells to astrocytes and oligodendrites or meningeal cells in the brain.

supporting

How do you name a benign mesenchymal neoplasm?

tissue type + “oma” (fibroma)

How do you name a malignant mesenchymal neoplasm?

tissue type + sarcoma (fibrosarcoma)

Sarcomas are typically ________, ________ tumors. There can be exceptions to this rule. Hemangiomas/hemangiosarcomas tend to be ________ and ________ ________.

firm; white; fluctuant; dark red

What is this showing?

hemangioma

What is this showing?

hemangiosarcoma

What is this showing?

osteosarcoma

specific category of mesenchymal tumors

round cell tumors

What are the 5 cell types in round cell tumors?

L
M
P
H
T

• lymphocytes (B and T cells)

• mast cells

• plasma cells

• histiocytoma

• transmissible venereal tumor

leukocytic (including lymphocytic) tumor that is originating in the bone marrow, which ends up in the peripheral blood stream

leukemia

True or false: There is no benign lymphocytic neoplasm, though some forms of lymphoma are referred to as indolent (slow course of progression) whereas others are very aggressive.

true

Lymphomas are typically of what origin? What is an exception?

T or B cell; some can be de-differentiated enough that they do not express those markers

What are the 2 separate patterns of lymphomas?

1. D

2. C

• diffusely enlarges an organ

• creates homogenously soft off white bulging tumors on a cut section

What is this showing?

lymphoma

terminally differentiated B cells producing immunoglobulins

plasma cells

Plasma cell tumors or plasmacytomas are typically ________ and ________ in clinical course. They can be ________.

cutaneous; benign; extracutaneous

How does multiple myeloma appear on serum protein electrophoresis?

hyperglobulinemia + monoclonal gammopathy

Multiple myeloma has what type of cell infiltrate?

plasma cell

What else is seen in multiple myeloma?

H
O
B

• hypercalcemia

• osteolytic bone lesions

• bence jones proteinuria

What is this showing?

multiple myeloma

tumor that is neither benign nor malignant and have variable biologic behavior

mast cell tumor

What is significant about canine mast cell tumor? What does it mean?

they are graded; the higher the grade, the more aggressive the clinical course

What are the types of grading scales?

2 tier and 3 tier grading scales

2 tier grading scale

Kiupel (low vs. high)

3 tier grading system

Patnaik (I is low, II is intermediate, III is high)

What is this showing?

mast cell tumor

benign cutaneous tumor in dogs that is commonly found on the head and limbs of young dogs, though old dogs can get it too and is described as a button tumor

histiocytoma

What cell is involved in histiocytomas?

langhan’s cells (type of histiocyte)

True or false: Histiocytomas will self regress given time or after traumatized.

true

What is this showing?

histiocytoma

What is transmissible venereal tumor (TVT) thought to arise from? What abnormalities do these cells have?

genetic alteration of canine histiocytes; chromosomal abnormalities

How is TVT transmissible?

through direct contact

Where does TVT occur?

at mucocutaneous junctions

What are the possible outcomes with TVT?

S
I
M

• spontaneous regression

• indolent growth

• metastatic form (frequently fatal)

What is this showing?

transmissible venereal tumor (TVT)

transmissible tumor in tasmanian devils that has a similar concept to TVTs and is decimating the population

tasmanian devil facial tumor

How is tasmanian devil facial tumor spread?

by biting

True or false: Some devils have been found with partial immunity to tasmanian devil facial tumor.

true

What is this showing?

tasmanian devil facial tumor

From where are neural crest tumors derived?

neural crest cells from the neuroectoderm

What are the cell types involved with neural crest tumors?

M
A
S
G

• melanocytes (melanoma)

• adrenal medullary cells (pheochromocytoma)

• schwann cells (schwannoma)

• ganglion cells (ganglioma)

Neural crest tumors are neither ________ nor ________. Therefore, tumors of these types are named differently. Typically, they are still named with oma but malignant is added as a pre-fix for aggressive variants.

mesenchymal; epithelial

What is this showing?

neural crest tumor

True or false: Some malignant neoplasms are difficult to determine the origin because they are so poorly differentiated (anaplastic).

true

Mixed tumors are believed to arise from what? What are they capable of?

single pluripotent or totipotent stem cell; differentiating into a variety of mature cell types

What is this showing?

benign mixed mammary tumor

What do teratoma arise from?

totipotent germ cells

In teratoma, what is usually expressed in the neoplasm?

all three embryonic cell lines

What is this showing?

teratoma

two separate tumor types that are in one location colliding and are originating from two separate cell types

collision tumors

What is this showing?

collision tumor

True or false: Tumor-like masses are not neoplastic but can look like it.

true

mature normal tissues/components in normal locations there is just a lot more present than normal or the structures appear slightly dysplastic

hamartoma

What is an example of hamartoma?

collagenous hamartoma

normal tissue in an abnormal location

choriostoma (aka ectopic)

What is this an example of?

choriostoma (corneal dermoid)