Page 557 - Concise Pathology for Exam Preparation ( PDFDrive )

542 SECTION II Diseases of Organ Systems

• Flattened follicular epithelium with abundant colloid results in an enlarged, colloid
rich gland (colloid goitre).
Clinical features
• Patients are usually clinically euthyroid
• Main symptoms are due to mass effects
2. Multinodular goitre (MNG)
• Repeated episodes of hyperplasia and involution lead to irregular enlargement of thyroid
with formation of nodules.
• MNG may be nontoxic or toxic depending on the secretion of T 3 and T 4 .
• Normal thyroid cells are heterogeneous with respect to response to TSH and ability to
replicate. Thyroid cells with high-intrinsic growth potential replicate actively.
Steps in the evolution of MNG are given in (Flowchart 20.6):

Thyroid cells with high-intrinsic growth potential
Active replication Mutations in TSH signalling pathways
Autonomous growth

Formation of polyclonal and monoclonal nodules

Uneven follicular hyperplasia and accumulation of colloid

Tensions and stresses

Rupture of follicles and vessels

Haemorrhage, scarring and calcification
FLOWCHART 20.6. Evolution of a multinodular goitre.

Gross morphology (Fig 20.1)
• Multinodular, asymmetrically enlarged thyroid
• May exert lateral pressure on midline structures (trachea and oesophagus)
• Growth behind sternum and clavicles labelled ‘intrathoracic or plunging goitre’

Haemorrhage

Colloid
filled
nodules

FIGURE 20.1. Gross picture of a MNG showing multiple nodules of variable size.
mebooksfree.com