Pathology mock Flashcards
Scenario: A 60 year old female patient presents at OPD clinic with unilateral firm facial swelling raising the right earlobe. Facial nerve examination is normal.
What is the most likely diagnosis?
-Benign parotid neoplasm
What is the most common benign parotid neoplasm?
Pleomorphic adenoma
What is the differential diagnosis of unilateral parotid swelling?
Classify:
–> Infection
–> Neoplasm (benign or malignant)
–> Obstruction
Benign neoplasm
-Pleomorphic adenoma
-Warthin’s tumour
Malignant neoplasm
–> adenocarcinoma
–> adenoid cystic carcinoma
Obstruction
–>Sialectasis
Infection:
–> Parotitis
–> Mumps
What is the meaning of pleomorphic?
-Variety of histological features reflecting stromal and epithelial tissue elements
Describe the histological appearance of a pleomorphic adenoma
-Benign tumour of the parotid gland
-Consists of a mixture of ductal (epithelial) and myoepithelial cells
-Therefore shows both epithelial and mesenchymal differentiation
Can pleomorphic adenoma turn malignant? How? What is the most common type of parotid malignancy?
Malignant pleomorphic adenoma is:
–> carcinoma ex pleomorphaic adenoma
Theories on how this develops include:
–> exposure to radiation
–> accumulation of genetic mutations
Most common type is
-Mucoepidermoid carcinoma
From your examination, what signs would make you suspect malignant transformation in a parotid swelling?
-Rapidly enlarging mass
-Fixity to underlying tissues
-Ulceration
-Facial nerve palsy
-Presence of lymph nodes
In general what are the characteristics of a malignant neoplasm?
-Rapidly enlarging
-Less well differentiated/anaplasia
-Tendency of invasion (local structures and lymphatics/blood vessels)
-Ability to metastasise
What simple test in clinic can help differentiate between benign and malignant tumours?
-FNAC
What are the cytological features which would raise suspicion of malignancy?
-Loss of normal tissue architecture: normal epithelial cells are arranged in orderly fashion and often have polarity; nucleus is in specific location
-Pleomorphism (variation in nucleus or cell size)
-Hyperchromatic nuclei (increase in nuclear DNA content with subsequent darker H and E staining
-High nucleus to cytoplasmic ratio (due to increase in nucleus size)
-Anaplasia (loss of differentiation)
-Increased rate of mitosis (irregular or bizarre mitosis)
-Giant cells (some malignant cells can coalesce into giant cells)
-Ischaemic necrosis (tumour cells outgrow their blood supply)
What is the difference between cytology and histology?
Cytology is the study of individual cells
Histology is the study of tissue architecture, with background parenchyma and connective tissue
Cytology: useful in grading
Histology: useful in staging
Interpret the following FNAC findings:
–> langerhans cell + lymphcyte + necrotic material
–> Brown pigmented cells + epithelioid cells
–> Reed sternberg cell + lymphoid cell + blast cell
–> langerhans cell + lymphcyte + necrotic material: granuloma –> TB
–> Brown pigmented cells + epithelioid cells: malignant melanoma
–> Reed sternberg cell + lymphoid cell + blast cell: lymphoma
What are the advantages and disadvantages of histology and cytology?
Describe the meaning of sensitivity
The percentage of true positives. So a sensitive test has a low percentage of false negatives
The sensitivity of a test is its ability to classify a diseased person as diseased
Describe the meaning of specificity
The percentage of true negatives.
Ability of a test to classify non diseased patients as normal
How can you differentiate between carcinoma and lymphoma?
By immunohistochemistry
What is immunohistochemistry in simple words?
It is a method of localising specific antigens in tissues or cells based on antigen antibody recognition
How does immunohistochemistry work?
The antibodies are usually linked to an enzyme or fluorescent dye. When the antibodies bind to the antigen in the tissue sample, the enzyme or dye is activated, and the antigen can then be seen under a microscope
What is the type of antigen-antibody reaction in immunohistochemistry?
Complement fixation
How can you rule out malignancy intraoperatively?
Can be ruled out with frozen section
What is a frozen section?
A pathological laboratory procedure to perform rapid microscopic analysis of a specimen
How is the specimen fixed in frozen section?
-Specimen is taken and frozen -20 to 30 degrees
-It is then fixed in gel like medium called OCT
-Subsequently the frozen specimen is cut with a microtome and picked up on a glass slide and stained
Needle stick injury: what would you do?
Wound
-Wound is allowed to bleed under running water and washed with soap
-Assess incident risk(e.g. intravascular vs suture needle, depth of injury)
-Assess source patient: take a history for risk factors of blood borne infection.
-Take bloods from patient after consent if indicated
-File incident report and speak to occ health
-Document
What are the post operative complications of parotidectomy?
-Facial nerve injury
-Frey’s syndrome
-Fistula
-Great auricular nerve damage
What is Frey’s syndrome
-Parasympathetic disruption: fibres which normally supply parotid gland join with sympathetic fibres which supply scalp and face
-Results in gustatory sweating (erythema and sweating instead of salivation)
