Thyroid cancer learning notes

[Thyroid] Cancer cases rise in Fukushima but experts unsure on the cause - Maan Pamintuan  Features, National - Japa Daily Express Dec 23, 2013

http://japandailypress.com/cancer-cases-rise-in-fukushima-but-experts-unsure-on-the-cause-2341371/

Fifty-nine young people from Fukushima Prefecture have either been diagnosed or suspected to have thyroid cancer but experts are still unsure if nuclear radiation is to blame for their illness. They were tested by the prefectural government along with 239,000 others at the end of September and those diagnosed were under 18 years old when the nuclear meltdown at the Fukushima Daiichi plant happened in March 2011.

A leading newspaper reported that most experts in a meeting conducted by the Japan’s Environment Ministry are not sure if the radiation leaks from Fukushima are the culprit for thyroid cancer in the children, as they believe that it’s too soon for the exposure to have any effect on them yet. Toshide Tsuda, a professor of epidemiology at Okayama University warned the government that there is a huge probability of increase in cases as such in the future and said that, “the rate at which children in Fukushima prefecture have developed thyroid cancer can be called frequent, because it is several times to several tens of times higher” and compared numbers of cancer cases all over Japan from the period of 1975 to 2008 with the rate in Fukushima and showed that annual average in those years were 5 to 11 people (late teens to early 20s) for every 1 million.

Tetsuya Ohira, a professor of epidemiology in Fukushima Medical University however, opposed the statistics, saying it “was not scientific to compare the Fukushima tests with cancer registry statistics.” Even officials from the prefecture have ruled out the likelihood that the increase in cancer cases was because of radiation exposure and compared it to the Chernobyl disaster of 1986 where cases of thyroid cancer increase around 4 to 5 years after the accident. Dr. Choi Kin, former president of the Hong Kong Medical Association said that, “radioactive iodine is linked to thyroid cancer. Through the intake of food, people may absorb and accumulate it inside glands.” But while children are more susceptible to absorb it because they are still growing, saying that the radioactive iodine came form the nuclear disaster than the normal environment is yet to be proven.

[via South China Morning Post]




Ominous Thyroid Cancer Spike in Fukushima Youth - by s.e. smith December 2, 2013

http://www.care2.com/causes/ominous-thyroid-cancer-spike-in-fukushima-youth.html

When Japan’s Fukushima reactor began to experience trouble in the wake of a devastating earthquake and tsunami, the world watched in growing horror as the island nation desperately tried to avoid a nuclear disaster.

Almost from the start, efforts seemed plagued with problems, in a combination of unpreparedness, poor facility maintenance and unavoidable incidents that compounded the problems at Fukushima, creating a growing radiation zone that endangered citizens, livestock and the earth itself. Now, more than two years after the horrific events of March 2011, the nation is still struggling with the fallout: quite literally, in the case of an alarming medical trend emerging among Japanese minors.

Since June of this year, six children who were minors at the time of the Fukushima disaster have been diagnosed with thyroid cancer, which is an unusually high rate, especially when paired with a suspected 10 additional cases. 44 cases in total have been diagnosed since the start of the Fukushima Daiichi disaster, though the overall baseline rate of thyroid cancer in Japanese children remains at one to two in a million.

Japanese government officials claim that this uptick in diagnoses cannot be attributed to the Fukushima disaster, arguing that while radiation does build up in the thyroid gland and can cause a cancer risk, it takes several years to manifest. They’re pointing to data from the Chernobyl disaster, where cancer rates didn’t begin to radically spike for approximately five years, to suggest that these cases are unrelated to the nuclear event. This, of course, raises the question of what could be causing the artificially high thyroid cancer rate if it’s not Fukushima.

Some critics argue that the increase in diagnoses can be attributed to the use of a more sensitive testing technique. As is common with the development of new medical testing technologies, the sensitivity of the thyroid cancer screening being used in Japan is much higher than that used in the past. Consequently, it may be catching much more than traditional tests, thus leading to rate inflation that doesn’t reflect the true thyroid cancer rate. These concerns require further investigation, as if they are true, children may be receiving unnecessarily aggressive treatments for benign cellular changes.

If the government is wrong, which many outside critics (as well as Japanese residents themselves) believe, it could be looking at a steady climb in cancer rates, without adequate preparation. It insists that radiation exposure for most of the population was very low, too low to cause significant health risks, and an estimated 90% of radiation-exposed people aren’t eligible for the free lifetime screenings offered by the Tokyo Electric Power Company and the government. This means not only that citizens will be missing out on opportunities for early diagnosis and treatment, but also that the government will lose out on the opportunity for a large study cohort that might provide more insight into cancer rates in the wake of the Fukushima disaster.

The government’s desire to put Fukushima behind it is perhaps not surprising, as the disaster marked a horrible event in the nation’s history, one particularly dark given that this is not the first time Japan has been overshadowed by radiation. In the wake of the nuclear bombs dropped on Hiroshima and Nagasaki by the United States, the country struggled both with the legacy of radiation and the war itself, and was likewise eager to minimize the public profile of hibakusha, “bomb affected people,” those who developed illnesses as a result of radiation exposure.

In the case of Fukushima, the disaster represents substantial failings on the part of the government as well as TEPCO, and both parties would be happy to see the event taken out of the limelight. A rise in cancer diagnoses would have the opposite effect, especially when these cases involve cancer among children.

Japan’s government must rise to the challenge and make a thorough epidemiological study of the cancer cluster possibly emerging in Fukushima to determine its root causes, find out who else should be considered for cancer screening, and address the issue head-on, rather than hiding from it.




Fukushima: Japan’s Cut-Price Nuclear Cleanup: Human Error, Plummeting Morale and Worker Exodus 福島は割引清掃

http://www.globalresearch.ca/fukushima-japans-cut-price-nuclear-cleanup/5356796

Read more: http://www.care2.com/causes/ominous-thyroid-cancer-spike-in-fukushima-youth.html#ixzz2oTXOnL3N





Thyroid Ultrasound Top Ten Pathology - Ramin Javan, MD, James E. Machin, MD, Robert S. McGinnis, MD, Mohammed Moinuddin, MD, Marc Sarti, MD.

https://www.med-ed.virginia.edu/courses/rad/Thyroid_Ultrasound/index.html

Baptist Memorial Hospital and University of Virginia Health Sciences Center Department of Radiology

This web tutorial is designed to serve as an interactive and high-yield source regarding the challenges facing radiologists in dealing with thyroid nodules that are so commonly seen in daily practice and especially more and more commonly found incidentally. An attempt is made to simplify approach to nodules regarding follow-up and management recommendations, as well as the role of fine needle aspiration and nuclear medicine. A number of promising new techniques are also discussed regarding this issue.

DISCLAIMER

The discussion of sonographic appearances have been mostly directly adapted from "Ultrasound of Thyroid Nodules" by Desser TS and Kamay, as it appears in the Ultrasound Clinics April 2009 issue. All radiological images, are from the Baptist Memorial Hospital, unless otherwise noted.


Thyroid - University of Virginia Health Sciences Center ***

https://www.med-ed.virginia.edu/courses/rad/Thyroid_Ultrasound/01intro/intro-01-02.html

Anatomy

The thyroid gland is an H-shaped organ composed of two lobes joined by a narrow isthmus located just below the laryngeal cartilages. The normal thyroid weighs approximately 15 to 25 g, with each lobe 4 to 6 cm in length and 1.3 to 1.8 cm in thickness. The isthmus measures less than 4 to 5 mm.

The gland is bordered laterally by the common carotid arteries and SCM muscles, anterolaterally by the jugular veins, anteriorly by strap muscles and posteriorly by the longs coli muscles. It is supplied by the superior thyroidal branch of the external carotid artery and the inferior thyroid branch of the subclavian artery. The recurrent laryngeal nerve runs along the inferior thyroid artery.

Microscopically, the thyroid parenchyma is organized into follicles, hollow spheres of epithelial cells enclosing a protein-rich material termed colloid. Thin fibrous septations divide the normal thyroid into lobules composed of 20 to 40 follicles each about 50 to 500 mm in size.

Thyromegaly is present whenever the transverse or AP diameter exceeds 2 cm or when parenchyma extends anterior to the carotids.

Physiology

The thyroid gland synthesizes, stores, & secretes the thyroid hormones, principally thyroxine (T4) and to a lesser extent triiodothyronine (T3). Iodine trapped by Na-I cotransporter in cell membrane and transported to apical membrane (via transporter). Thyroglobulin is produced in stored in follicle. Thyroid peroxidase (TPO) ionizes iodine and links it to thyroglobulin covalently, a process called organification, leading to monoiodotyrosine, diodotyrosine, etc. Iodine is trapped, oxidized and covalently bound to tyrosines in thyroglobulin, a process which is vital in thyroid hormone production. Thyroid gland function is controlled by hypothalamic TRH and pituitary TSH which are in turn regulated by the negative feedback of thyroid hormones.

Thyroglobulin levels are used to determine whether residual thyroid tissue is present in patients who have had thyroid ablation with radiation or surgery.

Clinical Significance

Thyroid carcinoma is the most frequent type of endocrine cancer (95% of all endocrine cancers) in the United States, with 33,500 new cases diagnosed each year (40 per million per year) but only 1,500 deaths annually (6 deaths per million per year), mainly due to uncommon, aggressive forms of the disease. Autopsy studies show that 50% of patients with a clinically normal thyroid have nodules. In the Framingham population study, nodules were found by palpation in 6.4% of women and 1.5% of men. By ultrasound, many more nodules are detected. Location and size of nodule, size of neck and skill of examiner affect detection on physical exam, which are usually greater than 1 cm. With current ultrasound technology, even nodules as small as 1 mm may be evident.

The only well-established risk factor for differentiated thyroid cancer is external head and neck radiation, especially during infancy. Papillary thyroid carcinoma may occur in several rare inherited syndromes, including familial adenomatous polyposis, Gardner's syndrome, and Cowden's disease. Malignancy is more common in adults > 60, men’s nodules are more likely to be cancer and malignancy is more common in children age > 10 more common than < 10.

The use of external-beam irradiation in children and young adults in the 1950s and 1960s for acne and tonsillitis has been shown to result in an increased incidence of papillary cancer, usually 15 years after exposure. Irradiation for soft tissue malignancy, such as Hodgkin’s lymphoma, have an increased incidence of thyroid nodules and cancer.

https://www.med-ed.virginia.edu/courses/rad/Thyroid_Ultrasound/01intro/intro-01-04.html

Sonography Technique

To visualize the thyroid gland optimally, the patient is placed in the supine position with a pillow underneath the shoulders to extend the neck slightly, allowing the head to rest on the examination table. The normal thyroid gland is uniformly echogenic relative to the overlying strap muscles of the neck.

A thyroid nodule is defined as a region of parenchyma sonographically distinct from the remainder of the thyroid and located within the confines of the echogenic thyroid capsule. When a nodule is detected, its size should be measured in three dimensions and the location within the thyroid gland (upper pole, mid-gland, lower pole) should be noted by the sonographer.

Several sonographic features are helpful for differential diagnosis, including nodule echogenicity, morphology, cystic change, presence of echogenic foci with comet-tail artifact representing colloid, presence and type of calcifications, and flow pattern (peripheral or central).

* A high-frequency (10–15 MHz) linear transducer is used. The highest frequency is used while still allowing adequate sonographic penetration.

Size and Multiplicity

Thyroid nodules become palpable when they reach approximately 1 cm in size. In nodules larger than 1 cm, no significant difference in the rate of malignancy in solid nodules is found by size, although higher rate of malignancy in nodules larger than 3 cm has been suggested.

The recent Society of Radiologists in Ultrasound consensus statement suggests that, rather than a fixed size threshold, sonographic features should be used to guide nodule selection for FNA. More suspicious sonographic features should trigger biopsy at small nodule size, whereas nearly completely cystic nodules without other suspicious features probably do not require biopsy at any size.

The presence of multiple nodules does not make thyroid carcinoma less likely, contrary to former teaching. In multinodular glands, each nodule should be scrutinized for suspicious features and selected for FNA on the basis of sonographic features, rather than size alone.

Growth Pattern

Interval follow-up is usually recommended for sonographically detected nodules, yet there are no data to suggest which growth rates or patterns are suspicious. Both benign and malignant nodules can increase or decrease in size. Solid nodules have been shown to be more likely to grow than cystic nodules. A significant interval growth warrants biopsy.

Calcification

Calcifications have been found in papillary, medullary, and anaplastic thyroid carcinomas as either psammoma bodies or as amorphous granular deposits. Of all the sonographic features associated with thyroid malignancy, microcalcifications are the most specific. Microcalcifications are defined as punctuate echogenic foci without acoustic shadowing or associated comet-tail artifact. The positive predictive value of a finding of microcalcifications in a thyroid nodule ranges from 24.3% to 70%.

Other types of calcification may also be present, namely coarse calcifications and peripheral calcifications. Although formerly considered a benign finding, eggshell calcifications have been reported in thyroid cancers. Coarse central calcifications are a common feature of medullary carcinoma, although this entity represents only 1 of 250 thyroid nodules. At this time, it appears that any calcification type warrants biopsy.

Echogenicity

Most thyroid carcinomas are hypoechoic relative to surrounding thyroid parenchyma, 78% to 86%. Hypoechogenicity is a sensitive sign but is nonspecific: 30.6% to 55% of benign nodules are also hypoechoic. An echogenic appearance is commonly associated with follicular neoplasms, both benign and malignant, but can also be seen in papillary cancers.

Cystic Changes and Ring-Down Artifact

Thyroid cancer is not common in predominantly cystic nodules. Nodules that are nearly completely cystic are virtually never cancers in the absence of other concerning features. Nevertheless, a cystic component may be seen in 13% to 26% of thyroid cancers. When FNA is to be performed on a cystic nodule, the biopsy should be targeted to the solid components. A "honeycomb’’ appearance of multiple cystic spaces bordered by numerous thin septations virtually always correlates with benign cytology on FNA. Punctate echogenic foci associated with comet-tail artifact (see below) representing inspissated colloid seems to be present only in benign cystic nodules.

Vascularity

In general, a peripheral flow pattern tends to be a feature of benign nodules, and malignant nodules tend to have internal vascularity, but there is considerable overlap. Marked internal vascularity may be more often present in malignant than benign nodules, but a great percentage of nodules with internal hypervascularity are benign. Furthermore, solid hypovascular nodules can be malignant. A cystic nodule without any internal flow, however, is unlikely to be a papillary carcinoma.

Moon HJ, et al (Radiology April 2010) concluded that vascularity itself or a combination of vascularity and grayscale US features was not as useful as the use of suspicious gray-scale US features alone for predicting thyroid malignancy. "Can Vascularity at Power Doppler US Help Predict Thyroid Malignancy?" by Moon HJ, et al.

.END