Other names:
1. Mixed tumour
2. Enclavoma
3. Branchiomma
4. Endothelioma
5. Enchondroma
Definition:
It is the most common benign tumour of salivary gland cells exhibiting the ability to differentiate to epithelial (ductal and non-ductal) cells to mesenchymal (chondroid, myxoid and osseous) cells.
Note:
It is a misnomer i.e. It is not actually a pleomorphic tumour because:
- There are myoepithelial cells which look pleomorphic but are not pleomorphic
- No two tumour of adenoma are similar
- This tumour doesn't arise from more than one cell
Histogenesis:
- It is derived from a mixture of ductal and myoepithelial element
- Various theories
A) Hubner and his associates:
"Myoepithelial cell is responsible for pleomorphic diversity of the tumour, including the production of the fibrous, mucinous, chondroid and osseous areas"
B) Regezi and his associates:
"Intercalated duct reserve cell can differentiate into ductal and myoepithelial cells and later mesenchymal metaplasia"
C) Dardick and his associates: (Most accepted theory)
"Neoplastically altered epithelial cells with the potential for multidirectional differentiation might be histo-genetically responsible for it".
Clinical features:
Age: 30 - 50 years (but any age), Avg: 43 years, M:F =2:3
Site: Parotid gland (superficial lobe) - most common
Others: Submandibular>Sublingual>Minor Salivary glands
Sign and Symptoms:
Nodule or mass which is:
- Small
- Painless
- Slowly growing
- Mobile
- Not fixed to overlying skin or deeper tissues
- Firm in consistency
- Skin seldom ulcerates
- Local discomfort
- Facial paralysis rarely
Histologic features:
Gross/ Macroscopic features:
- Have a incomplete fibrous capsule or unencapsulated
- Cut surface: Rubbery, flesh, mucoid or glistening with homogenous tan or white colour, area of hemorrhage and infarction can be seen
Microscopic features:
1. Consists of both glandular and mesenchymal elements
2. The glandular component (epithelium) forms ducts or cysts that may contain eosinophilic coagulum or may occur as small cellular nest, sheets of cells, anastomosing cords and foci of keratinizing squamous or spindle cells.
- Myoepithelial cells are major component which has variable morphology i.e. angular, spindle or round with eccentric nuclei and hyalinized eosinophilic cytoplasm resembling plasma cells (Hyaline cells)
3. Myxoid appearance: Myoepithelial cells shows mesenchyme like changes → extensive accumulation of mucoid material around myoepithelial cells giving myxoid appearance
4. Cartilaginous appearance: Due to vascular degeneration of these myoepithelial cells
Note:
Foote and Frazell Classification:
1. Mucoid
2. Muco-cellular
3. Predominantly cellular
4. Extremely cellular
Investigations: CT and MRI
Treatment:
1. Surgical excision
2. Superficial parotidectomy
3. Removal of submandibular gland if involved
Malignant transformation:
To carcinoma ex-pleomorphic adenoma
Clinical staging: TNM and AJCC 1997
Tx: Primary tumour cannot be assessed
T0: No evidence of Primary tumours
T1: Tumours < or = 2 cm without extraparenchymal extension
T2: Tumour > 2 cm < 4 cm (diameter)
T3: Tumour > 4cm < 6 cm with extraparenchymal extension
T4: Tumour invade base of skull, 7th cranial nerve and > 6 cm
N0: No regional lymph node metastasis
Nx: Regional lymph node can't be assessed
N1: Single ipsilateral node, < 3 cm
N2a: Single ipsilateral node > 3 <6 cm
N2c: Contralateral or bilateral lymph node <6 cm
N3: Lymph node > 6 cm
M0: No distant metastasis
Mx: Metastasis cannot be assessed
MCQS
(These MCQS are specially made for entrance examinations but also for study purpose)
1. Mixed tumour is
a. Pleomorphic adenoma
b. Warthin's tumour
c.Mucoepidermoid carcinoma
d. Acinic cell carcinoma
Correct answer is a.
2. Pleomorphic adenoma is a misnomer because:
a.There are myoepithelial cells which look pleomorphic but are not pleomorphic
b. No two tumour of adenoma are similar
c.This tumour doesn't arise from more than one cell
d. All of the above
Correct answer is d.
3. Tumour exhibiting the ability to differentiate to epithelial (ductal and non-ductal) cells to mesenchymal (chondroid, myxoid and osseous) cells is
a. Mucoepidermoid carcinoma
b. Warthin's tumour
c. Pleomorphic adenoma
d. Acinic cell carcinoma
Correct answer is c.
4. Most accepted theory for histogenesis of pleomorphic adenoma is given by
a. Hubner and his associates
b. Regezi and his associates
c. Dardick and his associates
d. None of the above
Correct answer is c
5. Most common site for pleomorphic adenoma is
a. Parotid gland
b. Submandibular gland
c. Sublingual gland
d. Minor salivary glands
Correct answer is a.
6. Most common site for pleomorphic adenoma is
a. Superficial lobe of parotid gland
b. Deep lobe of salivary gland
c. Submandibular gland
d. Sublingual gland
Correct answer is a.
7. Facial paralysis can be seen in
a. Mucoepidermoid carcinoma
b. Pleomorphic adenoma
c. Both a and b
d. None of the above
Correct answer is c.
8. Myxoid appearance histologically is the feature of
a. Pleomorphic adenoma
b. Warthin's tumour
c.Mucoepidermoid carcinoma
d. Acinic cell carcinoma
Correct answer is a.
9. Most common benign tumour of salivary gland is
a. Warthin's tumour
b. Pleomorphic adenoma
c.Mucoepidermoid carcinoma
d. Acinic cell carcinoma
Correct answer is b.
10. Eosinophilic coagulum within a cyst can be seen in
a. Warthin's tumour
b. Pleomorphic adenoma
c. Both a and b
d. None of the above
Correct answer is c.
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