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Surgical and Pathological Details of Fukushima Thyroid Cancer Cases Released on August 31, 2015

Below is an English translation of the information released by Fukushima Medical University at the August 31, 2015 meeting of the 20th Oversight Committee for the Fukushima Health Management Survey. It includes surgical and pathological details of the 96 thyroid cancer cases operated on at Fukushima Medical University as of March 31, 2015. (See this post for an English translation of the previous version released on November 11, 2014).

These 96 cancer cases, along with one case post-surgically diagnosed to be a benign nodule and 7 cases operated on at other medical facilities, comprise the 104 cases (99 from the first round and 5 from the second round screening) that had undergone surgeries as of the 19th Oversight Committee Meeting for the Fukushima Health Management Survey held on May 19, 2015. This information is essentially the most updated details of the surgical cases since only one more surgical case (papillary thyroid cancer; age and tumor size unknown) was added as of June 30, 2015 (probably due to the new school year starting in April in Japan), according to the information released at the most recent Oversight Committee meeting held on August 31, 2015. 


August 31, 2015

Regarding Surgically Indicated Cases

Shinichi Suzuki, M.D., Ph.D.
Chair, Division of Thyroid and Endocrine Surgery
Fukushima Medical University Hospital

As of March 31, 2015, 104 among those eligible for thyroid examination underwent surgery after being diagnosed to have “malignant or suspicious” tumors in the confirmatory examination. 97 cases were operated on at the Division of Thyroid and Endocrine Surgery, Fukushima Medical University and 7 at other facilities. As 1 of 97 cases turned out to be a benign nodule post-operatively, 96 thyroid cancer cases are discussed here. According to the pathological evaluation, 93 cases were papillary thyroid cancer and 3 were poorly differentiated thyroid cancer.

In the pre-operative diagnosis, tumor diameter was > 10 mm in 63 cases (66%) and and ≤10 mm in 33 (34%). Also, of 33 cases with tumor diameter ≤10 mm, lymph node metastasis, mild extrathyroidal extension, or distant metastasis were suspected in 8 (8%), not suspected (cT1acN0cM0) in 25 (25%). Of these 25 cases, 22 were suspected to be close to the trachea or the recurrent laryngeal nerve, or have mild extracapsular extension. The remaining 3 cases were operated on according to patients’ wishes, despite the recommendation of non-surgical follow-up observation.

Furthermore, 23 (24%) cases were positive for lymph node metastasis, and 2 cases (2%) were suspected of distant metastasis — multiple lung metastasis.

Surgical methods included total thyroidectomy in 6 cases (6%), and hemithyroidectomy in 90 cases (94%). Lymph node dissection was conducted in all cases, with 80% limited to the central compartment and 20% including lateral compartment. As much as possible, small-size incisions of 3 cm were used.

The post-surgical pathological diagnosis revealed 28 cases (29%) with tumor diameter ≤ 10 mm, excluding 14 cases with mild extrathyroidal extension. And 8 cases (8%) had no lymph node metastasis, extrathyroidal extension, or distant metastasis (pT1a pN0 M0). 

Of all 96 cases, mild extrathyroidal extension (pEX1) was seen in 38 cases (39%), and lymph node metastasis was positive in 72 cases (74%). No post-operative complications (post-surgical hemorrhage, permanent paralysis of recurrent laryngeal nerve, hypoparathyroidism, or hypothyroidism after hemithyoidectomy) were observed.

Due to a small number of pediatric thyroid cancer cases [in general], a strict comparison is not yet possible. However, in general, juvenile thyroid cancers are characterized by good prognosis despite a higher rate of lymph node metastasis, if appropriately treated. Pediatric thyroid cancers with pre-operative findings of large lymph node metastasis, marked extra thyroidal extension (EX2) and distant metastasis are considered to belong to a high risk group, and total thyroidectomy is recommended even when the cancer is localized to one side of the thyroid gland. However, when lymph node metastasis and mild extrathyroidal extension are not apparent pre-operatively but found in the post-operative pathological diagnosis for the first time, these findings are considered unrelated to the prognosis. Therefore, every case with these findings [i.e. post-surgical lymph node metastasis and mild extrathyroidal extension] does not necessarily have poor prognosis, but it is unclear if the prognosis would still be good without surgery, and these findings do not offer proof of unnecessary surgery. These discussions need to be carried out carefully, and we intend to follow the development of the examination further. Removal of the entire thyroid gland necessitates a continual use of the thyroid hormone medication, but removal of only one half of the thyroid gland preserves the thyroid function from the remaining half, making the thyroid hormone medication unnecessary and allowing patients to lead daily lives just as they did before surgery. Therefore, at FMU we perform hemithyroidectomy unless the case is clearly high risk, in an effort to maintain the quality of life (QOL) of the patients.


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