Head and neck tumours

Oral cavity: why Pakistan sees so much oral cancer

• More than 90% of oral cancers are squamous cell carcinoma. Pakistan has one of the world's highest rates because of areca nut chewing (betel quid or paan, gutka, supari), smokeless tobacco such as naswar, smoking and alcohol. The tumour typically arises in the buccal mucosa where the quid is held, or on the lateral tongue and floor of mouth.
• Areca nut stimulates fibroblasts to lay down collagen and inhibits its breakdown, causing oral submucous fibrosis: blanched, stiff mucosa with progressive trismus. It is premalignant.

• Presentation: non-healing ulcer with an indurated rolled edge, pain referred to the ear, cervical nodes. Spread is mainly to cervical lymph nodes.
• HPV-16 oropharyngeal cancer (tonsil, tongue base) affects younger non-smokers, is p16 positive and has a better prognosis.

Jaw tumours

• Ameloblastoma is an odontogenic epithelial tumour of the posterior mandible (molar–ramus region). X-ray shows a multilocular "soap bubble" radiolucency. It is locally aggressive and recurs if curetted, but rarely metastasises, so it is treated by resection with a margin.
• Odontogenic keratocyst (also posterior mandible, recurs, Gorlin syndrome) and dentigerous cyst (around the crown of an unerupted tooth) are the main differentials.

Larynx, nasopharynx and sinuses

• Laryngeal SCC is a smoking cancer. Glottic tumours (commonest) cause early hoarseness and rarely spread to nodes, because the cords have few lymphatics, so prognosis is good. Supraglottic tumours spread early to nodes. Hoarseness lasting more than 3 weeks needs laryngoscopy.
• Nasopharyngeal carcinoma: EBV and salted fish; neck mass, unilateral serous otitis media in an adult, epistaxis, cranial nerve palsies; treated with radiotherapy.
• Sinus adenocarcinoma: hardwood dust; nickel exposure.

Salivary gland tumours

• About 80% arise in the parotid, about 80% of parotid tumours are benign, and most benign ones are pleomorphic adenomas. The smaller the gland, the more likely a tumour is malignant.

• Why pleomorphic adenoma recurs after enucleation: its capsule is incomplete and finger-like projections (pseudopodia) pierce it. Shelling it out leaves these behind, and they regrow years later as multiple nodules. The correct operation is superficial parotidectomy with a cuff of normal tissue.
• Facial nerve palsy with a parotid mass means malignancy until proven otherwise. Parotidectomy complications: facial nerve injury, Frey syndrome (gustatory sweating from misdirected auriculotemporal fibres), great auricular numbness, salivary fistula.

Neck lump in an adult

• A persistent neck mass in an adult over 40 is metastatic SCC from the upper aerodigestive tract until proven otherwise. Investigate with ultrasound and FNAC and panendoscopy; avoid open excision biopsy before this. In Pakistan, TB lymphadenitis (matted nodes, cold or collar-stud abscess) is the main benign alternative.

Brain tumours

• Glioblastoma: commonest primary malignant brain tumour; butterfly lesion across the corpus callosum, necrosis with pseudopalisading; surgery, radiotherapy and temozolomide; poor prognosis.
• Gliomas (astrocytes, oligodendrocytes, ependymal cells) are GFAP positive, identifying glial origin. Astrocytoma is the commonest glioma.
• Meningioma: commonest benign intracranial tumour; extra-axial with a dural tail, psammoma bodies, women, NF2; it is the commonest brain tumour after cranial irradiation.
• Pilocytic astrocytoma: cerebellar cyst with mural nodule, Rosenthal fibres, excellent prognosis. Medulloblastoma: commonest malignant childhood brain tumour, cerebellar vermis, CSF drop metastases.
• Vestibular schwannoma: cerebellopontine angle, unilateral sensorineural deafness; bilateral in NF2. Oligodendroglioma: calcified, "fried egg" cells, 1p/19q codeletion.
• Craniopharyngioma (Rathke pouch remnant): calcified suprasellar mass, growth failure, field defect. Surgery near the hypothalamus can damage the ventromedial nucleus (satiety centre), causing hyperphagia, and the supraoptic and paraventricular nuclei, causing diabetes insipidus and thirst.
• Pituitary macroadenoma grows up from below and presses the crossing nasal fibres from the inferior retinas first. These fibres serve the upper temporal fields, so the first defect is bitemporal superior quadrantanopia, progressing to bitemporal hemianopia. Craniopharyngioma presses from above and affects the lower temporal fields first.
• Raised ICP: morning headache worse on coughing, vomiting, papilloedema, sixth nerve palsy. Dexamethasone reduces oedema; avoid LP.

Thyroid cancer

• Nodules are common and mostly benign. Assess with TSH, ultrasound (hypoechoic, microcalcification, irregular margin, taller than wide) and FNAC graded by the Bethesda system.

• Differentiated cancer: total thyroidectomy (lobectomy for small low-risk papillary), radioactive iodine, TSH suppression, follow-up with thyroglobulin.
• MEN 2: medullary carcinoma with phaeochromocytoma (the hypertension in "familial medullary carcinoma") plus hyperparathyroidism in 2A, or mucosal neuromas and marfanoid build in 2B. Exclude phaeochromocytoma before thyroid surgery; RET carriers have prophylactic thyroidectomy.

Remember Name the cell, and the spread follows: follicular cells give papillary (lymph) and follicular (blood); C cells give medullary (calcitonin).

Exam trap A thyroid nodule biopsy showing amyloid stroma points to medullary carcinoma, not anaplastic or follicular.

Exam trap Enucleating a pleomorphic adenoma leaves its capsular projections behind; recurrence is multinodular.

How FCPS asks about this

• Habit causing submucous fibrosis and oral SCC in Pakistan: areca nut chewing; erythroplakia carries the highest malignant risk.
• Soap-bubble multilocular radiolucency of posterior mandible: ameloblastoma, locally aggressive, rarely metastasises.
• Recurrence of an enucleated pleomorphic adenoma: projections pierce its incomplete capsule; do superficial parotidectomy.
• Commonest benign and commonest malignant salivary tumours: pleomorphic adenoma; mucoepidermoid carcinoma.
• First field defect with a pituitary macroadenoma: bitemporal superior quadrantanopia.
• Commonest brain tumours: metastases and glioblastoma in adults; infratentorial tumours in children; psammoma bodies in meningioma; GFAP marks glial cells.
• Thyroid cancer spread and markers: papillary lymphatic, follicular blood, medullary calcitonin with RET and MEN 2.