Struma ovarii overview

# Overview
Struma ovarii is a variant of dermoid tumors of the ovary in which thyroid tissue components constitute fro more than 50% of the overall tissue. Struma ovarii is comparatively  a rare tumor which amounts to 1% of all ovarian tumors and 2.7% of all dermoid tumors. Struma ovarii is a rare monodermal variant of ovarian teratoma. In 1889 by Boettlin. By observing the ovaries discovered the presence of thyroid follicular tissue in Struma ovarii. It is thought that Struma ovarii is mediated by activation of the mitogen activated protein kinase signaling pathway as a critical step in tumorigenesis. Malignant struma ovarii (MSO) are rare tumors which arise from ectopic thyroid tissue in the ovary which is benign. The cause of Struma ovarii has not been identified.  Struma ovarii must be differentiated from other diseases like benign and malignant ovarian neoplasm, ovarian cyst, endometrioma and tubo-ovarian abscess. In 2015, the incidence of struma ovarii is approximately 220-240 cases per 100,000 individuals worldwide. Risk factors in the development of Struma ovarii include elevated CA-125 levels, older age, postmenopausal status, and large tumor masses.  In cases of metastatic struma ovarii post total thyroidectomy along with radioiodine scanning and radioiodine ablation, the thyroglobulin levels must be monitored as a tumor marker, and diagnostic radioiodine scans should be done to screen for residual or recurrent disease. If left untreated Struma ovarii may lead to thyrotoxicosis. Advanced disease may lead to malignancy, metastases, excessive hormone production and may prove fatal. The most feared complication of struma ovarii is thyrotoxicosis. Other complications include due to metastasis of stroma oavrii. Prognosis is generally excellent under benign conditions and in malignant cases, adjuvant iodine-131 ablation with surgical extirpation has excellent prognosis. The most common presenting symptoms are pelvic pain, abdominal distension followed by abnormal vaginal bleeding. Surgery is the mainstay of treatment for Struma ovarii. For benign cases of struma ovarii the treatment is surgical resection only. For malignant cases of struma ovarii an adjuvant treatment modalities such as radioiodine therapy and external beam radiation are recommended.

# Historical Perspective
Struma ovarii, the tumor was first described in 1889 by Boettlin. By observing the ovaries, he discovered the presence of thyroid follicular tissue in them. Further reports thereafter were published by Gottschalk in 1899.

# Classification
Malignant Struma ovarii (MSO) are categorized into 3 subtypes namely, Classic variant of papillary thyroid carcinoma (cPTC), Follicular variant of papillary thyroid carcinoma (FVPTC) and Follicular thyroid carcinoma.

# Pathophysiology
It is thought that Struma ovarii is mediated by activation of the mitogen activated protein kinase signaling pathway as a critical step in tumorigenesis. Malignant struma ovarii (MSO) are rare tumors which arise from ectopic thyroid tissue in the ovary which is benign.

# Causes
The cause of Struma ovarii has not been identified.

# Differentiating Stroma of ovary from Other Diseases
Struma ovarii which is potentially malignant should be differentiated from an ovarian mass with cystic, solid, or mixed cystic and solid structure. Struma ovarii must be differentiated from other diseases like benign and malignant ovarian neoplasm, ovarian cyst, endometrioma and tubo-ovarian abscess.

# Epidemiology and Demographics
In 2015, the incidence of struma ovarii is approximately 220-240 cases per 100,000 individuals worldwide. Struma ovarii usually occurs in the age groups between 40-60 years. There is no racial predilection to Struma ovarii. Being a tumor of ovarian origin, struma ovarii occurs in females only.

# Risk Factors
Risk factors in the development of Struma ovarii include elevated CA-125 levels, older age (between 40 - 60 years), postmenopausal status, and large tumor masses.

# Screening
There is insufficient evidence to recommend routine screening for Struma ovarii. However, in cases of metastatic struma ovarii post total thyroidectomy along with radioiodine scanning and radioiodine ablation, the thyroglobulin levels must be monitored as a tumor marker, and diagnostic radioiodine scans should be done to screen for residual or recurrent disease.

# Natural History, Complications, and Prognosis
If left untreated Struma ovarii may lead to thyrotoxicosis. Advanced disease may lead to malignancy, metastases, excessive hormone production and may prove fatal. The most feared complication of struma ovarii is thyrotoxicosis. Other complications include due to metastasis of struma oavrii. Prognosis is generally excellent under benign conditions and in malignant cases, adjuvant iodine-131 ablation with surgical extirpation has excellent prognosis. In adults with differentiated thyroid cancer who are treated with high doses of radioiodine seem to have an excellent long-term prognosis.

# Diagnosis

## History and Symptoms
The most common presenting symptoms are pelvic pain, abdominal distension followed by abnormal vaginal bleeding. Other symptoms such as anepithymia, dyschesia, nausea, fever, intestinal obstruction, frequent micturition and ascites may also be seen.

## Physical Examination
Patients with Struma ovarii usually appear normal. Physical examination of patients with Struma ovarii is usually remarkable for palpable lower abdominal mass. Pelvic pressure related to a pelvic mass is observed. Struma ovarii appears to occur more frequently in the right adnexa. In some cases ascites may be observed.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of Struma ovarii include histopathologic studies and elevated CA-125 levels.

## Electrocardiogram
There are no ECG findings associated with Struma ovarii.

## X-ray
There are no x-ray findings associated with Struma ovarii. However, an x-ray may be helpful in the diagnosis of complications of Struma ovarii, such as pleural effusion.

## CT scan
CT scan of the pelvis may be helpful in identifying a mass in the pelvic cavity but may not hold much value in the diagnosis of Struma ovarii. However, a CT scan may be helpful in the diagnosis of complications of Struma ovarii.

## MRI
MRI may be helpful in the diagnosis of Struma ovarii. Findings on MRI suggestive of Struma ovarii include solid and cystic lesions.

## Ultrasound
Ultrasound  may be helpful in the diagnosis of Struma ovarii. Findings on an ultrasound are suggestive of Struma ovarii occurred more frequently (68.8%) in the right adnexa and was seen with a normal CA-125 level.

## Other Imaging Findings
Scintigraphy may be helpful in the confirmation of diagnosis of Struma ovarii.

## Other Diagnostic Studies
There are no other diagnostic studies associated with Struma ovarii.

# Treatment

## Medical Therapy
The mainstay of treatment for Struma ovarii is surgical therapy. Chemotherapy doesn't seem to have role in the regular management of papillary and follicular thyroid cancer. It is reserved for patients with progressive disease which is usually not controlled by surgery, I-131, or other treatment modalities. Adjuvant treatment modalities such as radioiodine therapy and external beam radiation are recommended.

## Surgery
Surgery is the mainstay of treatment for Struma ovarii. For benign cases of struma ovarii the treatment is surgical resection only. For malignant cases of struma ovarii an adjuvant treatment modalities such as radioiodine therapy and external beam radiation are recommended.

## Primary Prevention
There are no established measures for the primary prevention of Struma ovarii.

## Secondary Prevention
There are no established measures for the secondary prevention of Struma ovarii.