Write a short note on Pleomorphic Adenoma.

The Concept

The pleomorphic adenoma is the commonest salivary gland tumour, most often arising in the parotid. It is a benign tumour also called a 'mixed' tumour because it contains a mixture of epithelial cells and a myxoid/chondroid ('cartilage-like') stroma — the 'pleomorphic' (many-formed) appearance from which it takes its name. This mixed histology and its capsule are the keys to its behaviour and treatment.

Clinical Features

It presents as a slow-growing, painless, smooth, firm, mobile lump, classically over the angle of the jaw or in the parotid tail. Because it is benign, it does not cause a facial nerve palsy — the appearance of nerve weakness in a parotid lump should immediately raise suspicion of malignancy instead.

WHY It Must Not Be Enucleated

The defining surgical point is that although the tumour appears encapsulated, it has an incomplete capsule with microscopic finger-like ('pseudopod') extensions that project into the surrounding gland. If it is simply enucleated (shelled out), these extensions are left behind and the tumour recurs, often multifocally and harder to treat. Therefore it is removed by superficial parotidectomy (excising the tumour with a cuff of surrounding gland) while carefully preserving the facial nerve.

Malignant Transformation

A long-standing pleomorphic adenoma carries a small but real risk of malignant change to carcinoma ex-pleomorphic adenoma, suggested by a sudden increase in size, pain, fixation or facial nerve involvement in a previously stable lump — another reason these tumours are excised rather than watched indefinitely.

Malignant Transformation & Follow-up

The safest summary for the viva is: a benign but troublesome tumour that must be excised by superficial parotidectomy, never enucleated, with lifelong awareness that a stable lump which suddenly grows, becomes painful, fixes or causes facial weakness has probably undergone malignant transformation and needs urgent reassessment.

Microscopic & Surgical Correlation

On histology the pleomorphic adenoma shows a characteristic mix of epithelial and myoepithelial cells within a myxoid, chondroid or mucoid stroma, with the tumour bulging into its surrounding pseudo-capsule as microscopic pseudopods. This directly explains the surgical rule: because tumour extends beyond the apparent capsule, an adequate cuff of normal gland must be taken (superficial parotidectomy), and spillage during surgery must be avoided as it seeds recurrence. The clinician therefore treats even this benign tumour with an oncological respect for margins.

Management Decisions & Recurrence

If a pleomorphic adenoma does recur after inadequate surgery, it is characteristically multifocal and adherent, making re-operation difficult and increasing the risk to the facial nerve — which is exactly why the first operation must be done correctly. In the submandibular gland the equivalent treatment is excision of the whole gland. Longstanding or recurrent tumours are excised rather than observed because of the cumulative risk of malignant transformation, and any suspicious change prompts urgent imaging and biopsy.

The Bottom Line

Ultimately the pleomorphic adenoma is the archetypal 'benign tumour treated with oncological respect': confirmed by FNAC, removed by superficial parotidectomy with a cuff of normal gland, never enucleated or spilled, and watched for the rare late malignant transformation — principles that recur throughout salivary surgery.

Enucleation causes recurrence — the pseudocapsule is incomplete.

• Commonest salivary tumour; benign 'mixed' tumour (epithelial + myxochondroid stroma); usually parotid.
• Slow-growing, painless, smooth, mobile lump at the angle of the jaw/parotid tail; no facial nerve palsy (that suggests malignancy).
• Has an incomplete capsule with pseudopod extensions → recurs if enucleated.
• Treat by superficial parotidectomy preserving the facial nerve (not enucleation).
• Small risk of malignant change (carcinoma ex-pleomorphic adenoma) if long-standing.