Adenoid Cystic Carcinoma

Question 1

Prevelance

Answer 1

• Rare tumor, accounting for about 1% of all head and neck malignancies and about 10% of all tumors of the salivary glands
• The most commonly reported malignant tumor of the minor salivary glands (MSGs)
• Also one of the most common cancers of the major salivary glands (the parotid, submandibular and sublingual salivary glands)
• Most common malignant tumor in Submandibular salivary gland

Question 2

Epidemiology

Answer 2

Common in the 5th and 6th decade of life(mean age is 57).
Very rare in patients under 20

Affects both male and female equally

Question 3

Sites

Answer 3

50% occurs in minor salivary glands- most common site is the palate followed by paranasal sinuses

Submandibular gland is the commonly affected in major salivary glands, rarely occcurs in the parotid (2-3%)

Question 4

Etiology

Answer 4

There are no distinct risk factors, and smoking is not known to affect the incidence

Question 5

Clinical features

Answer 5

It has been described as “one of the most biologically destructive and unpredictable tumors of the head and neck”

Presenting symptoms are:
1. Slow growing mass
2. Pain attributed to its tendency for perineural invasion.

The pain is localized and is present even before a palpable tumor is seen (low grade dull ache gradually increasing with intensity).

Oro-antral fistula may be seen when occuring in palate

May cause ulceration

Facial nerve palsy may occur when tumor is in the parotid

Question 6

Pathology

Answer 6

(A) Cribriform pattern
Hematoxyphilic material is present in cyst-like spaces. Appearances simulating the Roman-bridge pattern seen in salivary duct carcinoma.

(C) Solid pattern
Largely basaloid tumor cells growing in sheets without lumina formation

Three grades were suggested:
1. Grade I, tumors with tubular and cribriform areas, but without solid components;
2. Grade II, cribriform tumors that were purely or mixed with >30% of solid areas; and
3. Grade III, tumors with a predominantly solid pattern.

Neural invasion can be seen even in early-stage tumors and has been regarded as an unfavorable prognostic factor, associated with distant metastasis and adverse final outcome

Question 7

Histology

Answer 7

Mixture of myoepithelial and ductal cells

Three patterns
1. Cribiform pattern
2. Tubular pattern
3. Solid pattern

Perineural invasion is the high characteristic of this tumour with swirling patterns around the nerve bundless

Cribifrom pattern has a Swiss Cheese appearance (Islands of basaloid epithelial cells that contain multiple cylindric cyst like spaces resembling swiss cheese)

Question 8

Investigations

Answer 8

1. Fine Needle Aspiration Cytology
   The finding of large globules of extracellular matrix, partially surrounded by basaloid cells
2. Diagnostic Imaging
   Computed tomography (CT) and/or Magnetic resonance imaging (MRI)

Question 9

Treatment and prognosis

Answer 9

Treatment
- Radical surgical excision ensuring free margins
- Post op radiation (does not change survival rate)

Prognosis
* 5 year overall survival (55 - 89%)
* High frequency of local and distant recurrence and poor long term prognosis
* Lung is most common site of distant metastasis (lung, bone, soft tissue)
* Tumors with solid pattern have the worst prognosis
* Maxillary sinus and Submandibular gland have the worst prognosis
* MX sinus and palatal tumors can invade upwards to the base of the brain

Death is usually from local recurrence and distant metastasis

Question 10

Differential diagnosis