Friday, May 5, 2017

Thyroid cancer - A Short Discussion

Thyroid cancer
occurs in all age groups, especially in persons who have had radiation treatment to the neck area. 
Papillary and follicular carcinomas are most common and are usually associated with prolonged survival.

Papillary carcinoma accounts for half of all thyroid cancers in adults; it’s most common in young adult females and metastasizes slowly. It’s the least virulent form of thyroid cancer. 

Follicular carcinoma is less common but more likely to recur and metastasize to the regional nodes and through blood vessels into the bones, liver, and lungs.
Medullary carcinoma originates in the parafollicular cells derived from the last branchial pouch and contains amyloid and calcium deposits. It can produce calcitonin, histaminase, corticotropin (producing Cushing’s syndrome), and prostaglandin E2 and F3 (producing diarrhea).
This rare form of thyroid cancer is familial, associated with pheochromocytoma, and completely curable when detected before it causes symptoms. Untreated, it progresses rapidly.
Seldom curable by resection, giant and spindle cell cancer (anaplastic tumor) resists radiation and metastasizes rapidly.

Predisposing factors include radiation exposure, prolonged thyrotropin stimulation (through radiation or heredity), familial predisposition, or chronic goiter.

Signs and symptoms
The primary signs of thyroid cancer are a painless nodule, a hard nodule in an enlarged thyroid gland, or palpable lymph nodes with thyroid enlargement. Eventually, the pressure of such a nodule or enlargement causes hoarseness, dysphagia, dyspnea, and pain on palpation.
If the tumor is large enough to destroy the gland, hypothyroidism follows, with its typical symptoms of low metabolism (mental apathy and sensitivity to cold). However, if the tumor stimulates excess thyroid hormone production, it induces symptoms of thyrotoxicosis (sensitivity to heat, restlessness, and hyperactivity).
Other clinical features include diarrhea, anorexia, irritability, vocal cord paralysis, and symptoms of distant metastasis.

The first clue to thyroid cancer is usually an enlarged, palpable node in the thyroid gland, neck, lymph nodes of the neck, or vocal cords. A patient history of radiation therapy or a family history of thyroid cancer supports the diagnosis. However, tests must rule out nonmalignant thyroid enlargements, which are more common.
Fine needle biopsy detects cancer cells.
Thyroid scan differentiates between functional nodes (rarely malignant) and hypofunctional nodes (commonly malignant) by measuring how readily nodules trap isotopes compared with the rest of the thyroid gland. In thyroid cancer, the scintiscan shows a “cold,” nonfunctioning nodule.
Other tests include computed tomography scan, ultrasonic scan, and serum calcitonin assay to diagnose medullary cancer. Calcitonin assay is a reliable clue to silent medullary carcinoma.
  • Total or subtotal thyroidectomy, with modified node dissection (bilateral or unilateral) on the side of the primary cancer (papillary or follicular cancer)
  • Total thyroidectomy and radical neck excision (for medullary, giant, or spindle cell cancer)
  • Radiation (with or without surgery)
  • Adjunctive thyroid suppression, with exogenous thyroid hormones suppressing thyrotropin production, and simultaneous administration of an adrenergic blocking agent such as propranolol, increasing tolerance to surgery and radiation
  • Chemotherapy for symptomatic, widespread metastasis is limited, but doxorubicin is sometimes beneficial.

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