51.1 Benign Tumours

• Usually present as solitary nodule or dominant nodule in MNG

• Middle-aged women

• Not premalignant

• Rarely become toxic

• Encapsulated

• Microscopic patterns:

Follicular

Microfollicular

Hürthle cell

Embryonal

• Malignancy excluded by ruling out capsular or vascular invasion on histology

51.2 Malignancy Risk Factors

• Family history of thyroid cancer

• Exposure to ionizing radiation

51.3 Malignant Tumours

51.3.1 Papillary Adenocarcinoma

• 80% of thyroid malignancy

• “Only” thyroid cancer in children

• 5th decade

• Presents as thyroid nodule

• Microcarcinoma <1 cm diameter

• Histological subtypes:

Pure papillary

Mixed papillary–follicular (most common)

Follicular

• Psammoma bodies in fibrous stalk

• Ground-glass “orphan Annie” nuclei

• High incidence of LNs in levels III to VII (60%)

• Primary tumour may be impalpable—therefore often presents with LNs

• 20% have pulmonary mets at presentation

• Bony mets less common

• More aggressive in older age groups—may invade larynx/trachea

• 10-year survival >90%

51.3.2 Follicular Adenocarcinoma

• 6th decade

• 20% of all thyroid malignancies

• Decreasing incidence in endemic goitre areas

• Commonly presents as solitary thyroid nodule

• May present with mets—bone/lung in 20 to 30%

• Non-vesicular nuclei

• Histology required following surgical resection to determine diagnosis

51.3.3 Hürthle Cell Tumours

• Aka eosinophilic/oncocytic/oxyphilic cell

• More aggressive variant of follicular ca (2% total)

• Is possibly a degenerative/metaplastic phenomenon

• Found in:

Nodular goitres

Chronic lymphocytic thyroiditis

Diffuse toxic goitre

Post-radiation

Post-chemotherapy

Aging thyroids

• Malignant tumours display capsular and vascular invasion

• May invade surrounding tissue and extrathyroid structures

• LN mets common

51.3.4 Medullary Thyroid Carcinoma

• 5% of all thyroid malignancies

• May occur as part of MEN syndrome:

MEN IIA

MEN IIB

Familial non-MEN

Sporadic

• Bilateral in 90% of cases with MEN

• LN mets in 25 to 30%

• Arise from parafollicular/C cells

• Calcitonin = tumour marker

• Uniform spindle-shaped cells with variable fibrous stroma on histology

• Account for <5% of all lymphoma

• Classically rapidly increasing swelling in neck of an elderly woman

• Immunocytochemistry needed to distinguish from anaplastic carcinoma

• Usually arises on background of chronic autoimmune thyroiditis

• Most are high-grade B-cell NHL

• Mostly stage I or II

• Occasionally thyroid involved in widespread systemic lymphoma

51.3.6 Anaplastic Cancers

• Elderly women

• Often long-standing enlargement of thyroid

• Rapid increase in size associated with pain referred to ear and hoarseness ± airway obstruction

• Aggressively malignant with high metastatic potential

• Commonly invade surrounding structures

• Most patients dead within 1 year of presentation

51.3.7 Metastatic Deposits

• Kidney and breast

51.4 Radiology

• CXR

Tracheal deviation

Mediastinal extension/LNs

Pulmonary mets

Co-morbidity

• USS

Tumour size

Diagnosing MNGs

Excludes contralateral disease

Evaluate complex cysts

Fine calcification 85 to 95% specific for papillary thyroid ca

Combined with FNA for initial diagnosis

Evaluate metastatic neck disease if suspected combined with FNA and thyroglobulin washout

• CT scan

Avoid the use of iodinated contrast media when performing CT scans. This may reduce the subsequent radioiodine uptake by thyroid tissue and therefore delay its use

Assess extent of larger tumours including larynx/trachea/oesophagus/major vessels

Demonstrates nodal deposits in neck/mediastinum

Direct retrosternal extension

Pulmonary mets

• MRI scan

Assess possible vessel involvement (MR angiography)

No contrast required

• Scintigraphy

Poorly specific and sensitive

Technetium-99m mostly used due to cost and availability

90% of nodules are cold

20% risk of malignancy in a cold nodule (50% if cyst excluded on USS)

Hot nodules unlikely to be malignant

¹²³I-MIBG used for suspected MEN

¹³¹I radioiodine used for post-operative ablation and to search for mets

51.5 Laboratory Investigations

• TFTs—mandatory

• Thyroid autoantibodies

May assist diagnosis of chronic lymphocytic thyroiditis

Predict post-operative hypothyroidism

Helps interpretation of thyroid function and thyroglobulin

Preop thyroglobulin not helpful

Serum calcium and calcitonin—if medullary ca suspected

51.5.1 Prognostic Factors

• The British Thyroid Association (Guidelines 2007) recommend either use of TNM staging or MACIS systems to determine when a patient is low risk or high risk for recurrence.

• TNM: Tumour size, node metastases, and distant metastases

• MACIS: Metastases, age at presentation, completeness of surgical resection, invasion (extra thyroidal), size

51.6 Poor Prognostic Factors for DTC

• Age > 45 years

• Male