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RESIDUAL FUNCTIONING THYROID TISSUE IN SURGICAL BED AND IN A THYROGLOASSAL DUCT REMNANT
Authored By: Garima Agrawal and Farrokh Dehdashti.
Patient: 34 year old female
History: 34 year old woman with T2 N0 follicular papillary carcinoma, status post total thyroidectomy and neck dissection. The patient received 100 mCi of I131radioactive ablation 5 days prior to the day of whole body I131 scintigraphy.
Image Size:[small][as-submitted]

Fig. 1
Whole body I131 scintigraphy (Anterior and posterior projections).

Fig. 2
Spot views of face and neck.

Fig. 3
Spect-CT images acquired a day after the whole body planar scintigraphy. Coronal spect images through the neck.

Fig. 4
Spect-CT images at the level of thyroid gland resection bed.

Fig. 5
Spect-CT images at the level of thyroid gland resection bed.

Fig. 6
Spect/CT images at the level of hyoid.

Fig. 7
MPR reconstruction of Spect-CT images.
Image Size:[small][as-submitted]

Findings:

Whole body planar I-131 scintigraphy: There is expected I-131 activity in the salivary glands, mouth and oropharynx. There are 3 foci of increased radiotracer uptake. One in the midline superior to the thyroid surgical bed, and the remaining other 2 foci more inferiorly, one being in midline and other to the left .

SPECT/CT imaging for better delineation of the multiple focal areas of increased radiotracer uptake was recommended.

I-131 imaging of the neck with SPECT/CT: Again seen is expected I-131 activity in bilateral submandibular glands and oral cavity.

There is focal area of increased uptake anterior to the hyoid bone in the midline. This area likely represents functioning thyroid tissue in the thyroglossal duct remnant.

A focal area of increased uptake is identified in the region of the thyroid surgical bed, on the left side, just superior to the surgical clips. Another focal area of increased uptake is identified in the region of the surgical clips on the right side.

DDx:

1. Functioning thyroid tissue in the surgical bed and in a thyrogloassal duct remnant.

2. Functioning thyroid tissue in the surgical bed with regional metastatic lymph nodes.

Diagnosis: Probable functioning thyroid tissue in a thyroglossal duct remnant and in bilateral surgical bed.
General Discussion:

As the thyroid gland descends from the foramen cecum to its location at the point below the thyroid cartilage, it leaves behind an epithelial trace known as the thyroglossal tract. The tract is normally resorbed during the 5th-10th gestational week. Incomplete involution of the thyroglossal tract and the remaining secretory epithelium creates the basis for the origin of a thyroglossal duct cyst (TGDC). A thyroglossal duct remnant can be a cyst, a tract or duct, a fistula, or an ectopic thyroid within a cyst or duct [1]. 70% of TGDC are diagnosed in childhood and 7% are diagnosed in adulthood [2].

Thyroid carcinoma arising in a thyroglossal duct cyst is very rare, affecting less than 1% of cysts [3]. This condition is rarely diagnosed preoperatively. Once diagnosed, therapy includes surgery, radioactive iodine and thyroid supression, as is the case for differentiated thyroid cancers.

Specific Discussion: I131 SPECT/CT has facilitated rapid, accurate, and confident assessment of radioiodine activity outside the expected biodistribution. Studies have shown that SPECT/CT has an incremental diagnostic value over planar imaging. On SPECT/CT images, central neck activity can be accurately characterized as thyroid remnant or locoregional disease, and the number of equivocal foci on planar assessment is reduced resulting in a substantial impact on clinical management. Similarly in the detection of distant metastatic disease, the superior lesion localization and additional CT-derived anatomic information obtained increase reader confidence, assisting clinical management decisions [4-9].
References:

1.  Peretz A, Leiberman E, Kapelushnik J, Hershkovitz E. Thyroglossal duct carcinoma in children: Case presentation and review of the literature. Thyroid. 2004;14:777–785. doi: 10.1089/1050725041872945.

2.  Yang YJ, Wanamaker JR, Powers CN. Diagnosis of papillary carcinoma in a thyroglossal duct cyst by fine needle aspiration biopsy. Arch Pathol Lab Med. 2000.

3.  Dedivitis RA, Guimareas AV. Papillary thyroid carcinoma in thyroglossal duct cyst. Int Surg. 2000;85:109–201.

4.  Ruf J, Lehmkuhl L, Bertram H, et al. Impact of SPECT and integrated low-dose CT after radioiodine therapy on the management of patients with thyroid carcinoma. Nucl Med Commun 2004;25 : 1177-1182

5.  Tharp K, Israel O, Hausmann J, et al. Impact of I-131 SPECT/CT images obtained with an integrated system in the follow-up of patients with thyroid carcinoma. Eur J Nucl Med Mol Imaging2004; 31:1435 -1442

6.  Schmidt D, Szikszai A, Linke R, Bautz W, Kuwert T. Impact of 131I SPECT/spiral CT on nodal staging of differentiated thyroid carcinoma at the first radioablation. J Nucl Med. 2009;50:18–23.

7.  Wong KK, Zarzhevsky N, Cahill JM, Frey KA, Avram AM. Incremental value of diagnostic 131I SPECT/CT fusion imaging in the evaluation of differentiated thyroid carcinoma. AJR Am J Roentgenol. 2008 Dec;191(6):1785-94.

8.  Grewal RK, Tuttle RM, Fox J, Borkar S, Chou JF, Gonen M, Strauss HW, Larson SM, Schöder H. The effect of posttherapy 131I SPECT/CT on risk classification and management of patients with differentiated thyroid cancer.
J Nucl Med. 2010 Sep;51(9):1361-7. Epub 2010 Aug 18.

9.  Yamamoto Y, Nishiyama Y, Monden T, Matsumura M, Satoh K, Ohkawa M. Clinical usefulness of fusion of I-131 SPECT and CT images in patients with differentiated thyroid carcinoma. J Nucl Med2003; 44:1905 -1910

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Additional Details:

Case Number: 281101Owner(s): Garima Agrawal and Farrokh DehdashtiLast Updated: 02-07-2013
Anatomy: Face and Neck   Pathology: Neoplasm
Modality: CT, Nuc MedAccess Level: Readable by all users, writable by NucMed Certifiers
Keywords: trnm, thyroid scintigraphy, thyroglossal duct, functioning thyroid tissue

Case has been viewed 26 times.
Certified by Farrokh Dehdashti on 11-21-2011

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