MedPix Medical Image Database COW - Case of the Week Case Contributor: Paul J Cunningham Affiliation: Madigan Army Medical Center

MedPix No: History Pt Demographics: Age = 43 y.o. Gender = man Anterior neck mass, present for years. Now has palpable lymph nodes on the right. Downloaded by (-1)

MedPix No: EXAM & LABS

Thyroglossal Duct Cyst Contrast enhanced CT images at several levels through the neck, demonstrate a largely cystic mass anterior to the hyoid bone, extending toward the right. The scans also demonstrate significant lymphadenopathy posterior to the right sternocleidomastoid muscle, with multiple punctate calcifications within the mass. - - Downloaded by (-1)

Thyroglossal Duct Cyst Contrast enhanced CT images at several levels through the neck, demonstrate a largely cystic mass anterior to the hyoid bone, extending toward the right. The scans also demonstrate significant lymphadenopathy posterior to the right sternocleidomastoid muscle, with multiple punctate calcifications within the mass. - - This image also demonstrates a small focus of calcification, apparently in a soft tissue mass attached to the wall of the cyst. (it is marked with an arrow on the image withheld for the quiz.) Downloaded by (-1)

Thyroglossal Duct Cyst, Ectopic Thyroid Tissue Contrast enhanced CT images at several levels through the neck, demonstrate a largely cystic mass anterior to the hyoid bone, extending toward the right. The scans also demonstrate significant lymphadenopathy posterior to the right sternocleidomastoid muscle, with multiple punctate calcifications within the mass. - - This image also demonstrates a small focus of calcification (arrow), apparently in a soft tissue mass attached to the wall of the cyst. Downloaded by (-1)

Thyroglossal Duct Cyst, Ectopic Thyroid Tissue Contrast enhanced CT images at several levels through the neck, demonstrate a largely cystic mass anterior to the hyoid bone, extending toward the right. The scans also demonstrate significant lymphadenopathy posterior to the right sternocleidomastoid muscle, with multiple punctate calcifications within the mass. - - Downloaded by (-1)

FINDINGS Contrast enhanced CT images at several levels through the neck, demonstrate a largely cystic mass anterior to the hyoid bone, extending toward the right. The scans also demonstrate significant lymphadenopathy posterior to the right sternocleidomastoid muscle, with multiple punctate calcifications within the mass. There is a small focus of calcification (arrow), apparently in a soft tissue mass attached to the wall of the cyst.

DIFFERENTIAL DIAGNOSIS What is your Differential Diagnosis? The differential diagnosis of cystic neck masses includes: infection (bacterial-suppurative or fungal-granulomatous); neoplastic, and other congenital masses. One useful differential feature is that below the hyoid bone, TDC are typically embedded within the strap muscles - whereas many other cystic neck masses, such as necrotic lymph nodes and abscesses, are usually more superficial. In addition, TDC are usually midline (they are the most common midline neck mass) and branchial cleft cysts are usually lateral, usually related to the anteriomedial border of the sternocleidomastoid muscle. Cystic hygromas (lymphangiomas) are usually multiloculated. Although TDC are sometimes septated, they are not as complex as lymphangiomas. - - The differential diagnosis of calcified neck masses includes granulomatous infections, as well as neoplastic calcifications in papillary adenocarcinomas.

Diagnosis: thyroglossal duct cyst Dx Confirmed by:

DISCUSSION DIAGNOSIS: Papillary thyroid carcinoma arising in a thyroglossal duct cyst. - - DISCUSSANT: Mahmood F. Mafee, M.D. - - The thyroglossal duct cyst (TDC) is the most common congenital cystic mass of the neck, making up 90% of such lesions. Although they usually present in childhood, they are also seen in adults. They represent remnants of the normal developmental embryology of the thyroid gland. - - Development of the thyroid gland begins with an epithelial lined invagination into the base of the tongue at the foramen cecum, at approximately 3 weeks. This thyroglossal duct descends through the tongue mesoderm, and passes through the developing tongue muscles, the floor of the mouth, and anterior to the hyoid bone. The duct then makes a recurrent loop either through the hyoid, or behind it, before finally descending in the anterior neck. By 7 weeks, the thyroid usually reaches its normal location, and the duct itself usually regresses by weeks gestation. - - Interruption of this normal migration can result in ectopic thyroid tissue or persistence of portions of the thyroglossal duct. Most commonly, the TDC is infrahyoid (65%), 20% are at the level of the bone, and 15% are suprahyoid. The cyst fluid is secreted by the ductal epithelium, and accumulates inside of the closed pocket. In about 1/3 to 2/3 of TDC, there is functional thyroid tissue related to the wall of the cyst. This functioning tissue can be seen on radionuclide scanning. The persistent remnants of the thyroid within the cyst may develop carcinomas, at roughly the same 4% rate as thyroid tissue within the normally located gland. About 80% of these are papillary thyroid carcinomas - a type that calcifies frequently. Because of the epithelium lining the TDC, squamous cell carcinomas are also possible. - - Surgical excision is the treatment of choice, and typically the Sistrunk procedure is recommended. The Sistrunk operation includes removal of the entire tract of the TDC, resection of the middle portion of the hyoid bone, and excision of the tongue base. There is no evidence that papillary carcinoma of the TDC behaves differently from that in the normal thyroid gland. Preoperative staging may include localization of all functioning thyroid tissue with radioisotope imaging. In this case, cervical adenopathy was present, and a radical node dissection was performed. - - SUGGESTED READINGS - - Som PM, Bergeron RT Eds:Head and Neck Imaging. Chap 8, Section Two Reede DL, Holliday RA, Som PM, Bergeron, RT: Nonnodal Pathologic Conditions of the Neck. pgs Mosby St. Louis Feghali, J.G., Levin, R.J., Llena, J., Bradley, M.K., and Kantrowitz, A.B. Aggressive Papillary Tumors of the Endolymphatic Sac: Clinical and Tissue Culture Characteristics. Am J Otology 16(6): , Megerian, C.A., McKenna, M.J., Nuss, R.C., Maniglia, A.J., Ojemann, R.G., Pilch, B.Z., and Nadol, J.B. Endolymphatic Sac Tumors: Histopathologic Confirmation, Clinical Characterization, and Implication in von Hippel-Lindau Disease. Laryngoscope 105: , Tibbs Jr., R.E., Bowles Jr., A.P., Raila, F.A., Fratkin, J.D., and Hutchins, J.B. Should Endolymphatic Sac Tumors Be Considered Part of the Von Hippel-Lindau Complex? Pathology Case Report. Neurosurg 40(4): , Mukherji, S.K., Albernaz, V.S., Lo, W.W., Gaffey, M.J., Megerian, C.A., Feghali, J.G., Brook, A., Lewin, J.S., Lanzieri, C.F., Talbot, J.M., Meyer, J.R., Carmody, R.F., Weissman, J.L., Smirniotopoulos, J.G., Rao, V.M., Jinkins, J.R., and Castillo, M. Papillary endolymphatic sac tumors: CT, MR imaging, and angiographic findings in 20 patients. Radiology. 202: , Ouallet, J.C., Marsot-Dupuch, K., Van Effenterre, R., Kujas, M., and Tubiana, J.M. Papillary adenoma of endolymphatic sac origin: a temporal bone tumor in von Hippel-Lindau disease. Case report. J.Neurosurg. 87: ,