Thyroid adenoma overview

# Overview
Thyroid adenoma is a benign tumor of the thyroid gland. Thyroid adenoma was first discovered by Fabricius, in 1619 when he described that thyroid enlargement causes midline neck swelling. Thyroid adenoma may be classified according to the histology into 3 subtypes/groups follicular adenoma, papillary adenoma, and signet cell adenoma. Thyroid adenoma arises from epithelial cells of thyroid gland, that are normally involved in secretion of thyroxine hormone. The most common gene involved in the pathogenesis of thyroid adenoma is THADA gene. Common causes of thyroid adenoma include iodine deficiency, chronic inflammation, and genetic mutation of THADA gene. Thyroid adenoma must be differentiated from other thyroid disorders such as multinodular goiter, grave's disease, Hashimoto's disease, medullary cell carcinoma, De Quervain's thyroiditis, thyroid lymphoma, and acute suppurative thyroiditis. The incidence of thyroid adenoma is estimated to be 9 million cases annually in United States. Females are more commonly affected with thyroid adenoma than males. Common risk factors in the development of thyroid adenoma are family history of thyroid adenoma, exposure to radiation, lack of iodine in diet, smoking, and Hashimoto's thyroiditis. Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as excellent. The hallmark of thyroid adenoma is swelling in front of the neck. A positive history of radiation exposure and family history of thyroid adenoma  is suggestive of thyroid adenoma. The most common symptoms thyroid adenoma include cough and hoarseness of voice. On ultrasound, thyroid adenoma is characterized by halo sign or smooth margin of thyroid, hyperechoic nodules, and normal reactive cervical nodes. Fine needle aspiration biopsy may be helpful in diagnosis of thyroid adenoma. Findings on fine needle aspiration biopsy suggestive of thyroid adenoma include cystic changes, fibrosis, and areas of hemorrhage. The mainstay of therapy for thyroid adenoma is supportive therapy and regular monitoring.

# Historical Perspective
Thyroid adenoma was first discovered by Fabricius, in 1619 when he described that thyroid enlargement causes midline neck swelling.

# Classification
Thyroid adenoma may be classified according to the histology into 3 subtypes/groups follicular adenoma, papillary adenoma, and signet cell adenoma.

# Pathophysiology
Thyroid adenoma arises from epithelial cells of thyroid gland, that are normally involved in secretion of thyroxine hormone. The most common gene involved in the pathogenesis of thyroid adenoma is THADA gene.

# Causes
Common causes of thyroid adenoma include iodine deficiency, chronic inflammation, and genetic mutation of THADA gene.

# Differentiating thyroid adenoma from other Conditions
Thyroid adenoma must be differentiated from other thyroid disorders such as multinodular goiter, grave's disease, Hashimoto's disease, medullary cell carcinoma, De Quervain's thyroiditis, thyroid lymphoma, and acute suppurative thyroiditis.

# Epidemiology and Demographics
The incidence of thyroid adenoma is estimated to be 9 million cases annually in United States. Females are more commonly affected with thyroid adenoma than males.

# Risk Factors
Common risk factors in the development of thyroid adenoma are family history of thyroid adenoma, exposure to radiation, lack of iodine in diet, smoking, and Hashimoto's thyroiditis.

# Natural History, Complications and Prognosis
Depending on the extent of the tumor at the time of diagnosis, the prognosis of thyroid adenoma may vary. However, the prognosis is generally regarded as excellent. Common complications of thyroid adenoma include hyperthyroidism,thyrotoxicosis, hemorrhage, thyroid cyst, and superior vena cava obstruction.

# Diagnosis

## Study of Choice
There is no single diagnostic study of choice for the diagnosis of thyroid adenoma, but thyroid nodules can be diagnosed based on an ultrasound examination of the neck, a screening serum TSH level, and fine needle aspiration biopsy.

## History and Symptoms
The hallmark of thyroid adenoma is swelling infront of the neck. A positive history of radiation exposure and family history of thyroid adenoma is suggestive of thyroid adenoma. The most common symptoms thyroid adenoma include cough and hoarseness of voice.

## Physical Examination
Patients with thyroid adenoma usually appear normal. Physical examination of patients with thyroid adenoma is usually remarkable for solitary, non-tender nodule in the midline of neck, which is smooth, soft, and mobile.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of thyroid adenoma include decreased thyroid stimulating hormone, elevated calcitonin, and decreased calcium.

## Ultrasound
On ultrasound, thyroid adenoma is characterized by halo sign or smooth margin of thyroid, hyperechoic nodules, and normal reactive cervical nodes.

## Other Imaging Findings
Other diagnostic studies for thyroid adenoma include thyroid scan, which demonstrates hot, cold, and functioning nodule.

## Biopsy
Fine needle aspiration biopsy may be helpful in diagnosis of thyroid adenoma. Findings on fine needle aspiration biopsy suggestive of thyroid adenoma include cystic changes, fibrosis, and areas of hemorrhage.

# Treatment

## Medical Therapy
The mainstay of therapy for thyroid adenoma is supportive therapy and regular monitoring.

## Surgery
Thyroid lobectomy is recommended for all patients who develop pressure symptoms of thyroid adenoma.

## Prevention
There is no established method for prevention of thyroid adenoma.