Thyroid tumors

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Thyroid tumors
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Classification of thyroid tumors

• A. Benign tumors
• Follicular thyroid adenoma
• B. Malignant thyroid tumors
• Papillary carcinoma (75-85).
• Follicular carcinoma (10-20).
• Medullary carcinoma (5).
• Anaplastic carcinoma (less than 5).
• Lymphoma.

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Follicular adenoma
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• Adenomas of the thyroid are typically discrete,
  solitary masses. With rare exception, they are
  derived from follicular epithelium and so might
  all be called follicular adenomas.
• Although the vast majority of adenomas are
  nonfunctional, a small proportion produce thyroid
  hormones and cause clinically apparent
  thyrotoxicosis.

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• Gross features
• The typical thyroid adenoma is a solitary,
  spherical, encapsulated lesion that is well
  demarcated from the surrounding thyroid
  parenchyma.

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Follicular adenoma
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• Follicular adenomas average about 3 cm in
  diameter, but some are smaller and others are
  much larger (up to 10 cm in diameter).
• In freshly resected specimens, the adenoma bulges
  from the cut surface and compresses the adjacent
  thyroid.

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• The neoplastic cells are demarcated from the
  adjacent parenchyma by a well-defined, intact
  capsule. These features are important in making
  the distinction from multinodular goiters, which
  contain multiple nodules on their cut surface
  produce less compression of the adjacent thyroid
  parenchyma, and lack a well-formed capsule.

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Adenoma

• Multinodular goiter

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• Microscopic features
• 1. Macrofollicular adenoma formed of opened
  acini containing colloid
• 2. Microfollicular adenoma formed of small acini
  with scanty colloid.
• - Most cases are mixed.

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Follicular adenoma
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• Complications
• 1. Toxic transformation (2ry toxic goiter).
• 2. Malignant transformation (thyroid carcinoma).

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Thyroid carcinoma
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• Carcinomas of the thyroid are relatively uncommon
  in the United States, accounting for about 1.5
  of all cancers.
• Most cases occur in adults, although some forms,
  particularly papillary carcinomas, may present in
  childhood.
• A female predominance has been noted among
  patients who develop thyroid carcinoma in the
  early and middle adult years, perhaps related to
  the expression of estrogen receptors on
  neoplastic thyroid epithelium.

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Types of thyroid carcinoma

• Papillary carcinoma (75-85).
• Follicular carcinoma (10-20).
• Medullary carcinoma (5).
• Anaplastic carcinoma (less than 5).
• Lymphoma.

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• Most thyroid carcinomas are derived from the
  follicular epithelium, except for medullary
  carcinomas the latter are derived from the
  parafollicular or C cells.

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Risk Factors for thyroid carcinoma

• 1. Ionizing radiation High dose x-rays of the
  neck or face during infancy or teenage years is a
  risk factor specially for papillary carcinoma
• 2. Old standing multinodular goiter is a risk
  factor for follicular carcinoma.
• 3. Hashimoto thyroiditis is a risk factor for
  lymphoma.

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Papillary Carcinoma

• The most common type.
• Females outnumber males, 31.
• Highest incidence in women in midlife.
• Commonly metastasizes to neck and mediastinal
  lymph nodes.
• lt5 of patients have distant metastases at time
  of diagnosis. Lung is most common site

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Gross features

• Unencapsulated tumor nodule with ill-defined
  margins
• Tumor typically firm and solid, sometimes with
  papillary growths.

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• Histopathology
• closely packed papillae which have fibrovascular
  cores.
• Psammoma bodies which is a laminated
  calcification.
• Nuclei are oval or elongated, pale staining with
  ground glass appearance .

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Papillary carcinoma of thyroid
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Papillary Thyroid Cancer nuclei are oval or
elongated, pale staining with ground glass
appearance
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Psammoma bodies within the tumor
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Follicular Thyroid Carcinoma

• Second most common type of thyroid cancer
• Early spread by blood to the bones, lungs, and
  central nervous system.
• Usually does not spread to the lymph nodes

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• Gross picture
• - encapsulated, solitary mass.

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Microscopic picture neoplastic follicles
invading the capsule and the blood vessels
outside the capsule
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Capsular infiltration malignant follicles
invade pink fibrous capsule
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Vascular infiltration the neoplastic follicles
invades blood vessel outside the capsule
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Anaplastic Thyroid Cancer

• Often occurs in the elderly people.
• Tumor is typically hard, poorly circumscribed,
  and fixed to surrounding structures.
• Extremely aggressive.

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Medullary Thyroid Carcinoma

• Tumor arising from the calcitonin-secreting
  C-cells of the thyroid gland.
• characterized by presence of pink amyloid in
  between malignant cells.

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Medullary Thyroid Carcinoma characterized by
presence of pink amyloid in between malignant
cells.