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Figure 27.18 Follicular carcinoma, showing encapsulated tumour with invasion of a capsular vessel. The follicles lined by tumour cells are of
various sizes and there is mild pleomorphism.

has association with pheochromocytoma and parathyroid fibrovascular septa. Sometimes, the tumour cells may be
adenoma (multiple endocrine neoplasia, MEN II A), or with arranged in sheets, ribbons pseudopapillae or small
pheochromocytoma and multiple mucosal neuromas (MEN follicles. The tumour cells are uniform and have the
II B). The sporadic cases occur in the middle and old age structural and functional characteristics of C-cells. Less
(5th-6th decades) and are generally unilateral, while the often, the neoplastic cells are spindle-shaped.
familial cases are found at younger age (2nd-3rd decades) 2. Amyloid stroma: The tumour cells are separated by
and are usually bilateral and multicentric. amyloid stroma derived from altered calcitonin which can

2. Secretion of calcitonin and other peptides. Like normal be demonstrated by immunostain for calcitonin. The
SECTION III
C-cells, tumour cells of medullary carcinoma secrete staining properties of amyloid are similar to that seen in
calcitonin, the hypocalcaemic hormone. In addition, the systemic amyloidosis and may have areas of irregular
tumour may also elaborate prostaglandins, histaminase, calcification but without regular laminations seen in
somatostatin, vasoactive intestinal peptide (VIP) and ACTH. psammoma bodies.
These hormone elaborations are responsible for a number of 3. C-cell hyperplasia: Familial cases generally have
clinical syndromes such as carcinoid syndrome, Cushing’s C-cell hyperplasia as a precursor lesion but not in sporadic
syndrome and diarrhoea. cases.
3. Amyloid stroma. Most medullary carcinomas have Most medullary carcinomas are slow-growing. Regional
amyloid deposits in the stroma which stains positively with lymph node metastases may occur but distant organ
usual amyloid stains such as Congo red. The amyloid metastases are infrequent. The prognosis is better in familial
Systemic Pathology
deposits are believed to represent stored calcitonin derived form than in the sporadic form: overall 10-year survival rate
from neoplastic C-cells in the form of prohormone. is 60-70%.
Most cases of medullary carcinoma present as solitary
thyroid nodule but sometimes an enlarged cervical lymph Anaplastic Carcinoma
node may be the first manifestation. Undifferentiated or anaplastic carcinoma of the thyroid
comprises less than 5% of all thyroid cancers and is one of
MORPHOLOGIC FEATURES. Grossly, the tumour may the most malignant tumour in humans. The tumour is
either appear as a unilateral solitary nodule (sporadic form), predominantly found in old age (7th-8th decades) and is
or have bilateral and multicentric involvement (familial slightly more common in females than in males (female-male
form). However, sporadic neoplasms also eventually ratio 1.5:1). The tumour is widely aggressive and rapidly
spread to the contralateral lobe. Cut surface of tumour in growing. The features at presentation are usually those of
both forms shows well-defined tumour areas which are extensive invasion of adjacent soft tissue, trachea and
firm to hard, grey-white to yellow-brown with areas of oesophagus. These features include: dyspnoea, dysphagia
haemorrhages and necrosis. and hoarseness, in association with rapidly-growing tumour
Histologically, the features are as under (Fig. 27.19): in the neck. The tumour metastasises both to regional lymph
1. Tumour cells: Like other neuroendocrine tumours (e.g. nodes and to distant organs such as the lungs.
carcinoid, islet cell tumour, paraganglioma etc), medullary
carcinoma of the thyroid too has a well-defined organoid MORPHOLOGIC FEATURES. Grossly, the tumour is
pattern, forming nests of tumour cells separated by generally large and irregular, often invading the adjacent