Common pathology definitions

Question 1

What is an abscess?

Answer 1

-collection of pus
-surrounded by granulation or fibrous tissue

Question 2

What is pus?

Answer 2

Pus is a collection of neutrophils, together with dead or dying micro-organism

Question 3

What is a cyst, and how is this different from a pseudocyst?

Answer 3

-abnormal membranous sac containing a gaseous, liquid, or semisolid substance.
-This differs from a pseudocyst in that a pseudocyst lacks epithelial or endothelial cells.

Question 4

What is a sinus?

Answer 4

A sinus is a blind-ended track lined by granulation tissue, which normally connects an
abscess to the skin

Question 5

What is a stoma? How can they be classified?

Answer 5

A stoma is a surgical opening into a hollow viscus. It can be classified by anatomical site
(colostomy, ileostomy, urostomy, tracheostomy, gastrostomy), temporary vs permanent, or
the number of openings (loop vs end).

Question 6

What is an aneurysm?

Answer 6

An aneurysm is an abnormal, permanent, localised dilatation of a blood vessel to >1.5x its
normal diameter

Question 7

What are diverticula?

Answer 7

A diverticulum is an abnormal outpouching of a hollow viscus into the surrounding tissues

Question 8

What are the differences between a clot, a thrombus and an embolus?

Answer 8

A thrombus is defined as solid material formed from the constituents of blood in flowing
blood.

When formed in stationary blood this is termed a clot.

An embolus is defined as an abnormal mass of undissolved material that is carried in the
bloodstream from one place to another.

Question 9

What is necrosis?

Answer 9

Necrosis is defined as abnormal tissue death during life

Question 10

What are hypersensitivity reactions?

Answer 10

A hypersensitivity reaction represents an exaggerated response of the host’s immune system
to a particular stimulus

Question 11

What is a tumour marker?

Answer 11

A tumour marker is a substance which can found in the circulation of a patient with neoplasia

Question 12

What is a polyp?

Answer 12

A polyp is a pedunculated mass of tissue arising from an epithelial surface

Question 13

What is a neoplasm?

Answer 13

A neoplasm is an abnormal growth of tissue which displays:
Uncoordinated growth
Growth which exceeds that of the normal tissue
Growth which continues despite removal of the original stimulus

Question 14

What is hyperplasia?

Answer 14

Hyperplasia is an increase in the size of an organ or tissue through an increase in the
NUMBER of cells. The cells are of normal size and morphology

Question 15

What is hypertrophy?

Answer 15

Hypertrophy is an increase in the size of an organ or tissue through an increase in the SIZE of
the cells. The number of cells remains the same, as does the morphology.

Question 16

What is a hamartoma?

Answer 16

A hamartoma is a tumour-like malformation composed of a disorganised arrangement of
different amounts of tissue normally found at that site. It grows under normal growth
controls.

Question 17

What is metaplasia?

Answer 17

Metaplasia is a REVERSIBLE replacement of one fully differentiated cell type with another
differentiated cell type

Question 18

What is dysplasia?

Answer 18

Dysplasia is disordered cellular development characterised by increased mitosis and
pleomorphism but WITHOUT the ability to invade the basement membrane and metastasise

Note: Severe dysplasia = carcinoma-in-situ

Question 19

What are carcinomas and sarcomas?

Answer 19

A carcinoma is a malignant tumour of epithelial cells
A sarcoma is a malignant tumour of connective tissue

Question 20

What is a metastasis?

Answer 20

A metastasis is the survival and growth of cells that have migrated from a malignant tumour
to a site distant from the primary tumour

Question 21

What is a fistula?

Answer 21

A fistula is an abnormal communication between two epithelial surfaces (or endothelial
surfaces e.g AV fistula).