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Pediatric patient with cystic lesion of neck. (Pathologic Quiz Case).

A 13-year-old girl with a past medical history significant only for asthma presented with a midline neck mass deep to the skin and subcutaneous tissue and anterior to the hyoid bone. The patient reported that the mass had appeared 6 months previously, had increased in size rapidly during the last month, and was mildly tender. Physical examination revealed a golf-ball-sized lesion fixed to the hyoid bone in the anterior midline of the neck. The patient was basically asymptomatic and had no difficulty swallowing. Ultrasonography showed that the lesion was cystic and well circumscribed. The cystic lesion and an adjacent portion of hyoid bone were surgically excised. Examination of the surgical specimen revealed a 4.0 x 3.0 x 2.2-cm, thick-walled cystic structure that was filled with clear serous fluid. The cyst was generally smoothly lined, but a focal area of papillary projections was noted arising from the internal surface and projecting into the lumen. Histologic analysis revealed that the cyst had a thick fibrous wall, which was lined internally by a discontinuous monolayer of bland cuboidal to low columnar cells (Figure 1). In areas, the cuboidal epithelium became attenuated and appeared squamous. The papillary structures noted grossly consisted of fibrovascular cores lined by low columnar cells with optically clear nuclei, nuclear grooves, and occasional pseudoinclusions (Figures 2 and 3). A focal area of calcification was also identified. A small island of thyroid tissue consisting of variably sized, colloid-filled follicles (Figure 4) was present in the fibrous wall of the cyst adjacent to the area of papillary projections, but the 2 areas were separated by the fibrous wall of the cyst, and additional histologic sections showed no continuity between the 2 areas. No lymphoid tissue was identified in the specimen.

[FIGURES 1-4 OMITTED]

What is your diagnosis?

Pathologic Diagnosis: Papillary Carcinoma Arising in a Thyroglossal Duct Cyst

The finding of a midline cystic neck mass raised the clinical suspicion of a thyroglossal duct cyst. This impression was confirmed histologically by the presence of an epithelium-lined cyst with nonneoplastic thyroid tissue in its fibrous wall. The unexpected finding within the cyst of a papillary proliferation with optically clear nuclei, nuclear grooves, and nuclear pseudoinclusions is diagnostic of papillary carcinoma arising in the thyroglossal duct cyst. The papillary carcinoma was focal but well de, fined. Some areas of the carcinoma exhibited a true papillary morphology, while other areas ranged from a follicular pattern to a solid pattern. A focal calcification resembling a psammoma body was present in the area of papillary differentiation.

Thyroglossal duct cysts arise from a failure of complete atrophy of the primitive thyroglossal duct. These cysts are frequently connected to the hyoid bone and are therefore generally associated with upward movement on swallowing. (1) The lining of the cyst may range from cuboidal to ciliated columnar or even squamous epithelium, the latter likely representing a metaplastic process. In greater than 60% of cases, normal thyroid tissue can be found in association with the cysts. (2)

Papillary carcinoma of the thyroid is the most common malignancy of the thyroid gland proper in the pediatric age group. (3) Papillary carcinoma arising in a thyroglossal duct cyst, however, is rare in general, comprising less than 1% of all thyroid cancers and with slightly more than 100 cases reported in the medical literature. (4) Only 6 of these cases have occurred in the pediatric population. Papillary carcinomas have long been associated with radiation exposure, both accidental and therapeutic. No history of radiation exposure is present in the current case. Previous studies have suggested that papillary carcinoma arises from the thyroid tissue in the duct wall and not from the lining epithelium of the duct. (5) In this case, however, no connection was found between the nonneoplastic thyroid tissue and the carcinoma. Furthermore, the carcinoma appeared to be continuous with and to arise from the duct epithelium. Since the thyroid gland is endodermally derived and the thyroglossal duct may contain remnants of endoderm and ectoderm, (6) the current lesion may represent a neoplastic process of primitive ductal epithelium.

Current treatment of thyroglossal duct cysts is surgical, consisting of removal of the cyst along with, in most cases, the middle portion of the hyoid bone. Current treatment of papillary carcinoma arising in a thyroglossal duct cyst is basically the same. Most authors believe that thyroidectomy is unnecessary, citing the low incidence of carcinomas found in the thyroid glands of patients who have undergone thyroidectomy following a diagnosis of papillary carcinoma arising in a thyroglossal duct cyst. (5) Some authors, however, have postulated that cases described as papillary carcinomas arising in thyroglossal duct cysts actually represent cystic lymph node metastases from primary papillary carcinomas of the thyroid gland. (7) While this issue remains controversial, the current case has a true epithelial lining, nonneoplastic thyroid tissue in the cyst wall, and no associated lymphoid tissue, making the likelihood of a lymph node metastasis unlikely. Furthermore, the patient described underwent subsequent total thyroidectomy, and no carcinoma was identified in the thyroid gland. The patient is currently being followed on an out-patient basis.

References

(1.) Rosai J, Carcangiu M, DeLellis RA. Thyroid tissue in abnormal location. In: Rosai J, ed. Tumors of the Thyroid Gland. Washington, DC: Armed Forces Institute of Pathology; 1990:317-325. Atlas of Tumor Pathology; 3rd series, fascicle 9.

(2.) Livolsi VA, Perzin K, Savetsky L. Carcinoma arising in median ectopic thyroid (including thyroglossal duct tissue). Cancer. 1974;34:1303-1315.

(3.) Moir CR, Telander RL. Papillary carcinoma of the thyroid in children. Semin Pediatr Surg. 1994;3:182-187.

(4.) Yoo KS, Chengazi VU, O'Mara RE. Thyroglossal duct cyst with papillary carcinoma in an 11-year old. J Pediatr Surg. 1998;33:745-746.

(5.) Livolsi V. Surgical Pathology of the Thyroid. Philadelphia, Pa: WB Saunders Co; 1990:353-356.

(6.) deMello DE, Lima JA, Liapis H. Midline cervical cysts in children: thyroglossal anomalies. Arch Otolaryngol Head Neck Surg. 1987;113:418-420.

(7.) Katz AD, Hachigian MR Thyroglossal duct cysts: a thirty year experience with emphasis on occurrence in older patients. Arch Surg. 1988;155:741-743.

Accepted for publication March 15, 2001.

From the Department of Pathology, University of South Alabama, Mobile.

Reprints: Elliot Carter, MD, Department of Pathology, University of South Alabama Medical Center, 2451 Fillingim St, Mobile, AL 36617 (e-mail: ecarter@usamail.usamail.usouthal.edu).
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Author:McNeil, Janis P.; Carter, Elliott
Publication:Archives of Pathology & Laboratory Medicine
Date:Nov 1, 2001
Words:1048
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