Page 563 - Concise Pathology for Exam Preparation ( PDFDrive )

548 SECTION II Diseases of Organ Systems

• Widely invasive tumours commonly develop metastasis, and about 50% patients
succumb to their disease within 10 years.
• Minimally invasive follicular carcinoma has a 10-year survival greater than 90%.

Medullary Carcinoma
• Neuroendocrine neoplasm derived from the parafollicular or ‘C cells’.
Clinical features
• Secretes calcitonin, which has an important role in diagnosis and postoperative follow
up of patients.
• In addition, may secrete other polypeptide hormones, eg, somatostatin, serotonin and
vasoactive intestinal peptide (VIP).
• Sporadic lesions are common in adults (40–50 years); cases associated with MEN
syndrome are seen in younger patients/childhood.
• May present as/due to:
• A paraneoplastic syndrome, eg, diarrhoea due to excessive VIP or hypocalcaemia due
to increased serum calcitonin
• Mass symptoms
Gross morphology:
• Solitary/multiple lesions seen in both lobes of thyroid
• Bilateral and multicentric in a familial setting, and solitary and unilateral in a sporadic setting
• Firm, pale grey-tan and infiltrative
• Foci of haemorrhage and necrosis may be seen in larger lesions
Microscopy:
• Composed of polygonal to spindle-shaped cells, which may form nests, trabeculae and
follicles; rarely small, more anaplastic cells are the predominant cell type.
• Acellular amyloid deposits (derived from altered calcitonin) may be seen in the stroma.
• Multicentric C-cell hyperplasia is often seen in the surrounding thyroid in familial
medullary carcinoma thyroid (absent in sporadic medullary carcinoma).
• Electron microscopy shows membrane-bound, electron-dense granules.
Prognosis: Prognosis of familial cancers is worse than sporadic (familial cancers tend to be
multiple and are associated with C-cell hyperplasia or micromedullary carcinomas ,1 cm).
Anaplastic Carcinoma
It is an undifferentiated tumour derived from thyroid follicular epithelium.
Clinical features
• Presents as a rapidly enlarging bulky neck mass, which spread to contiguous structures
• Seen in older patients (mean age of 65 years)
• Fifty percent patients have a previous history of multinodular goitre
• Twenty percent have a previous history of a differentiated carcinoma
• Twenty to thirty percent have a concurrent differentiated thyroid tumour most
commonly PTC

Genetic defects
Differentiated tumours Anaplastic carcinoma
Loss of P 53
Morphology
Highly anaplastic tumour, which may show any of the following histological patterns:
• Giant cell pattern (large pleomorphic giant cells)
• Spindle cell (sarcomatoid) pattern
• Mixed spindle cell and giant cell pattern
• Small cell pattern
Prognosis: Commonly metastasizes to lungs; is aggressive and fatal.

PARATHYROID GLAND
• Derived from developing pharyngeal pouches that also give rise to thymus
• Four glands (two each at upper and lower poles of thyroid)

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