embryology and cancers

Question 1

What is the basic embryology of the pituitary gland?
2 parts
How does it grow?

Answer 1

Pituitary gland
Ectoderm and neurectoderm origins
Rathke pouch
Ectoderm- anterior pituitary
Out pocketing of ectoderm of the stomatodeum
Evagination of the roof of the pharynx
Grows dorsally towards the developing forebrain
Infundibulum
Neurectoderm- posterior pituitary
Neural tube component
Downward out growth of the forebrain towards the roof of the pharynx
Overall- ectoderm (rathke pouch) and neurectoderm (infundibulum

Question 2

What is the basic embryology of the tongue?
Where does it start?
Parts and arches?
innervation?- sensory and motor

Answer 2

Tongue
Lies partly in the oral cavity and partly in the pharynx
Very mobile
Lingual frenulum
Comprised of intrinsic and extrinsic muscles
Primordia of the tongue appears at the same time as palate begins to form, receives a component from each of the pharyngeal arches
The 2 lateral lingual swellings (arch 1)
3 median lingual swellings (arch 1 (tuberculum impar), 2 and 3 (cupola) , and 4 (epiglottal swelling))
Lateral lingual swellings over grow the tuberculum impar
The 3rd arch of the cupola over grows the 2nd arch
Extensive degeneration occurs so the tongue is free from the floor of the oral cavity- lingual frenulum remains
Sensory innervation
Anterior 2/3= CN V and IX
Posterior 1/3= N IX and X
Special sensory is VII
Chorda tympani is a branch of VII (nerve of second arch) but passes into first arch and though the middle ear
Motor innervation
Myogenic precursors migrate into the developing tongue – CN XII
Overall- forms in the floor of the pharynx with contributions from all 5 pharyngeal

Question 3

What is the basic embryology of the thyroid?
Begin
Migrate
Connected to
developmental issues

Answer 3

Thyroid gland
Primordium of the thyroid gland appears in the floor of the pharynx between the tuberculum impar and cupola
The final position is the anterior neck
Descent- Foramen cecum is the point of origin for the descent, bifurcates and descends as a bi-lobed diverticulum connected by the isthmus
Remains connected to the tongue by the thyroglossal duct at the pyramidal lobe in 50% of people
Can develop thyroglossal cyst and fistulae and ectopic thyroid tissue
Overall- midline diverticulum in the floor of the pharynx, migrates anterior to the pharyngeal gut, hyoid bone and laryngeal cartilage

Question 4

development of these structures e.g. thyroglossal cyst, ectopic thyroid tissue..

Answer 4

Thyroglossal cyst
The thyroglossal duct usually reseeds after the thyroid reaches its final position
However sometimes they do not disappear and leaves cavities or pockets which fill with mucus or fluid and can become enlarged and infected
May have difficulty swallowing or breathing
Ectopic thyroid tissue
Developmental defect where the thyroid due to excessive migration
May cause a cough, pain, difficulty sleeping, airway obstruction etc

Question 5

List the most common risk factors associated with head and neck cancer s (HNC) and thyroid cancers.

Answer 5

Heavy alcohol and tobacco use
Age- older people
Men more affected than women
Previous Epstein Barr virus infection (Nasopharyngeal)
Chewing of betel quid (Paan)
Prolonged exposure to certain inhalants e.g. hardwood
Sunlight or sun beds (lips)
HPV (oropharyngeal)- rising in young patients
Thyroid- irradiation exposure and family history

Question 6

Most common types of cancer in head and neck?

Answer 6

Squamous cell carcinomas in more than 90% of cases
Oral cavity, larynx and oropharynx more likely
Nasopharynx and laryngopharynx less likely
Salivary glands, nasal cavity and sinuses much rarer
Thyroid- irradiation exposure and family history

Question 7

Describe the common initial manifestations (i.e. typical presenting signs/symptoms)) of HNC, particularly those of the oral cavity, pharynx and larynx, and of thyroid cancers.

Answer 7

Vary greatly- depends on the location, structures involved, extent of cancer spread
Common initial manifestations
Unexplained painful mucosal ulcerations or lesions
Unexplained hoarseness of voice, dysphagia or odynophagia
Otalgia if pharynx or larynx
Cervical lymphadenopathy as easily spread to lymph nodes

Question 8

Outline the typical further investigations required to determine the diagnosis and severity of a HNC or thyroid cancer
Staging?
Appropriate treatment?

Answer 8

Clinical examination
Biopsy of lesion
If neck lump then can by biopsied by fine needed aspiration for cytology or core biopsy under ultrasound for guidance
Imaging
Evaluates the extent of primary cancer and involvement of other structures like lymph nodes
Endoscopic investigation if nasal cavity, pharynx or larynx
Enables direct visualization of the cancer and can biopsy
Staging systems can then be used to determine severity
TMN- Tumour size and location (T), degree of lymph node involvement (N) presence or absence of metastasis (M)
Can be stage I to stage IV
If patients have distant metastasis e.g. in lungs, survival greatly reduced and likely incurable
Helps determine appropriate treatment
E.g. surgical intervention (resectable or unresectable)
Early stage- surgery and radiotherapy
Late stage- surgery and adjuvant chemotherapy
Can vary from laser surgery to radial neck dissection where all ipsilateral lymph nodes, spinal accessory nerves, internal jugular vein and sternocleidomastoid are removed
Due to complexity of structures in the head and neck often significant implications on anatomical structures needed for eating, drinking, speaking and breathing
Need expert support
Will need a whole team to help support treatment, if too far advanced disease

Question 9

Outline the common causes of neck lumps (including but not limited to lymphadenopathy) and the clinical features associated with them (i.e.. key symptoms and clinical examination findings)
Lymphadenopathy
Pharynx cancer
larynx cancer
thyroid cancer

Answer 9

Lymphadenopathy
Swollen lymph nodes
Causes?
Infection e.g. cold, tonsillitis, glandular fever, measles, rubella, TB, HIV
Cancer
Symptoms?
Fever, runny nose, sore throat
Tender, swollen lymph nodes in neck, armpits and groin
Limb swelling and night sweats
Examination?
May see bulging lymph nodes
Palpate
If infectious may be firm, tender, enlarged and warm, skin may be red
If cancer may be firm, non-tender, matted, fixed, increase in size
Pharynx cancer
Symptoms- Lump, pain, problems swallowing, weight loss
Investigations- imaging with CT and MRI, PET, biopsy, feeding assistance
Treatment- Small tumour excise and repair, radiotherapy, larger tumours may need more extensive surgery
Larynx cancer
Symptoms- Dysphonia, dysphagia, referred Otalgia, glogus, neck lump, weight loss and cacexia
Investigations- imaging with CT and MRI, PET, biopsy, voice issue and swallowing problems
Treatment- small tumours resect, RT and chemo is medium, large may need laryngectomy
Thyroid cancer
Symptoms- lump in neck or thyroid, problems swallowing, feeling like they are being strangled, voice change
Investigations- triple assessment, Full Hx and Ex, imagine like ultrasound, needle testing of lumps (FNAC) advanced Ix
Treatment- thyroidectomy, radioactive iodine, radiotherapy or chemotherapy