Mock12 Parotid

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A 60-year-old female patient presented at the outpatient clinic with unilateral firm facial swell in raising the right ear lobe. Facial nerve examination was normal.

What's the most probable diagnosis?

Benign parotid swelling

What's the most common benign parotid neoplasm?

Pleomorphic adenoma

What's the differential diagnosis of a unilateral parotid Swelling?

Duct obstruction: salivary calculus, external ductal compression
Neoplasia: benign or malignant
Infective: mumps, parotitis.

What's the meaning of pleomorphic?

Pleomorphic means variation of size, shape, stain of cells or their nuclei

Describe pleomorphic adenoma appearance?

Benign tumours that consist of a mixture of ductal (epithelial) and myoepithelial cells, and therefore they show both epithelial and mesenchymal differentiation.

Can pleomorphic adenoma turn malignant?

Yes, in 5% of people in process called carcinoma ex-pleomorphic adenoma

How does it occur?

It occurs in long standing pleomorphic adenomas, with average age of recurrence after 20 years
Unclear etiological factors but has some theories like
exposure to radiation
accumulation of genetic instabilities

What's the most common malignant parotid tumour?

Mucoepidermoid carcinoma (15%)

From your examination, what clinical signs would make you suspect malignant transformation in a parotid swelling?

Facial nerve affection.
Rapid increase in size.
Fixity to underlying tissue and skin.
Skin ulcer
Presence of associated lymph nodes.

What are the characters of a malignant neoplasm in general?

Rapid increase in size.
Anaplasia (less differentiation or lack of differentiation).
Invade surrounding tissues
Metastasize to distant tissues.

Simple test in the clinic to help you differentiate?

FNAC

What are the cytological features that would raise concerns of malignancy? (anaplastic features)

Necrosis or haemorrhage
Increased atypical mitosis
Atypical polymorphic cell forms (varied size and shape of cells)
Hyperchromatism (nucleus is darkened due to increased concentration of DNA)
Increase nuclear to cytoplasmic ratio
Increase number of mitotic figures

What is the main difference between cytology and histology?

Cytology is the study of cellular structure and function
Histology is the study of tissue under the microscope

What are the advantages of each?
Cytology

+Cheap
+Simple
+Quick
+Less invasive

Histology

+More reliable
+Avoid unnecessary excisional biopsy
+Give information about tissue architecture
+Can differentiate between follicular adenoma and carcinoma
+Expensive

Interpret the following FNAC findings
Langerhans giant cell + lymphocytes + necrotic material?

Mycobacterium TB granuloma

Brown pigmented cells + epithelioid cells?

Malignant melanoma

Reed Sternberg cell + lymphoid cells + blast cells?

Hodgkin lymphoma

FNAC has a sensitivity of about 81% and a specificity of around 98%.

What's the meaning of: sensitivity, high sensitivity, specificity and high specificity?

Sensitivity

The ability of a test to correctly classify an individual as diseased (i.e. true positive rate)

High sensitivity test

Low number of false negatives results when applied to test population.

Specificity

The ability of a test to correctly classify an individual as disease-free (i.e. true negative rate).

High specificity test

Low number of false positives results when applied to test population.

How can you differentiate between carcinoma and lymphoma?

IHC

What's IHC in simple words?

It's method of localizing specific antigen based on Ag-Ab recognition.

How is it done?

The antibodies are usually linked to an enzyme or a 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.

How to rule out malignancy intraoperatively?

Frozen section

How is it done?

The surgeon takes a small piece from a tissue or tumour and send it for analysis
The pathologist freezes it and section it and immediately cut it
The section will be stained and reported immediately when the results come out

While doing FNAC a needle stick injury was encountered, what would you do?

The wound should be allowed to bleed under running water and wash with soap
Assess incident risk
Assess source patient
Take history if he has a possibility of any blood borne infection, take a blood sample from the patient if high risk after consent.
I would file an incident report and speak to occupational health for advice.
Documentation

What are the post-operative complications of parotidectomy?

7th CN palsy
Frey's Syndrome
Salivary fistula
Greater auricular nerve damage → numbness to earlobe.

What's Frey's syndrome? (Auriculotemporal syndrome)

Post-operative phenomena following salivary gland surgery
Resulting in gustatory sweating and facial flushing due to reinnervation of postganglionic fibres to sweat gland and cutaneous blood vessels.

10 years after surgery, the patient presented with a neck swelling? What's your differential diagnosis?

Possible recurrence with metastasis
Lymphoma
Carotid body tumour

isurg

Mock12 Parotid