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Cervical thymic cyst
CASE REPORTS SERGE A. MARTINEZ, MD Case Report Editor
Cervical thymic cyst MITCHELL B. MILLER, MD, and MICHAEL A. DE VITO, MD, Albany, New York
C e r v i c a l thymic cyst is a rare congenital anomaly that may be first seen as a neck mass in children. A review of the English literature reveals 91 case reports with a variety of initial signs and symptoms.l-9 We report a patient with an asymptomatic neck mass who was found to have a cervical thymic cyst. CASE REPORT
A 5-year-old girl sought treatment for a 2-month history of an enlarging, asymptomatic, left neck mass. On physical examination, the mass measured 4 x 5 cm and was smooth, mobile, and soft. Computerized axial tomography of the neck demonstrated a 4- x 5-cm cystic mass deep to the sternocleidomastoid muscle, extending from the angle of the mandible to the level of the cricoid cartilage (Fig. 1). The lateral wall of the hypopharynx was mildly displaced by the mass. A barium swallow was normal. A preoperative diagnosis of branchial cleft cyst was made. At surgery a 4- × 5- × 5-cm soft, lobulated, cystic mass was found deep to the anterior border of the sternocleidomastoid muscle, medial to the internal jugular vein and anterior but adherent to the common carotid artery and vagus nerve. A small portion of the mass extended inferiorly to the level of the clavicle. The mass was completely excised. Pathologic examination demonstrated thymic tissue with intrathymic cyst formation containing cholesterol crystals (Fig. 2). Her postoperative course was unremarkable. DISCUSSION
The thymus originates from the third branchial pouches in the sixth week of development. Thymic tubules rapidly elongate and descend along the thymopharyngeal tracts until they fuse in the midline at
From the Division of Otolaryngology, Albany Medical College. Received for publication April 8, 1994; accepted July 8, 1994. Reprint requests: Mitchell Miller, MD, Division of Otolaryngology, A-41, Albany Medical College, Albany, NY 12208. OTOEARYNGOL~-IEADNECKSURG 1995;i12:586-8. Copyright © 1995 by the American Academy of OtolaryngologyHead and Neck Surgery Foundation, Inc. 0194-5998/95/$3.00 + 0 23/4/58968 586
Fig, t. Axial computed tomography scan demonstrating 4- x 5-cm cystic mass deep to sternocleidomastoid muscle,
8 weeks. Migration continues inferiorly until the thymus rests in the superior mediastinum at 12 weeks. 1° Thymic tissue may be present anywhere along this route of descent. Cervical thymlc cyst is a rare entity with only 92 reported cases, including out own. However, the presence of asymptomatic thymic tissue in the neck is much more common, with a reported incidence of 30% in children at autopsy, s The scarcity of clinical cases may be explained by the fact that most cervical thymic tissue remains dormant. This thymic tissue can enlarge during childhood and may be first seen as a cervical mass. In 1938 Speer 11 proposed five theories for the pathogenesis of cervical thymic cysts: (1) they may
Oto[aryngology Head and Neck Surgery Volume 'I~2 Number 4
MILLER and DE VffO
587
Fig. 2. Thymic tissue containing cholesterol crystals with intrathymic cyst formation. [Hematoxylin and eosin; original magnification × 100,1
represent remnants of branchial clefts or the thymopharyngeal tract; (2) they may result from sequestration of thymic tissue during migration; (3) they may represent neoplastic change in the lymphoid or the surrounding tissues; (4) they may result from cystic degeneration of Hassall's corpuscles; (5) they may arise from lymphoid tissue that has arrested in various stages of thymic development. Most authors 4-7agree that the arrest of migration of thymic tissue along the thymopharyngeal tracts is primarily responsible for the formation of cervical thymic cysts. Thymic cysts can be unilocular or multilocular, and they may contain clear or bloody fluid. The cyst wall may be lined with spindle-shaped columnar or cuboidal cells, with thymic tissue adjacent to the cyst. Cholesterol crystals and giant cell reaction are common. These features distinguish thymic cysts from branchial cleft cysts2 The cervical thymic cyst was present on the left side in 68% of cases, on the right side in 25%, and in the midline in 7%. Most patients (87%) had only painless swelling; however, 13% of patients had a variety of symptoms including hoarseness, dysphagia, and stridor. Respiratory distress in neonates caused by large cervical thymic cysts has been re-
ported? The average age at surgery was less than 10 years. The cysts were typically located in the anterior triangle, either anterior or deep to the sternocleidomastoid muscle. Fifty percent of thymic cysts extended into the mediastinum. A Preoperative computed tomography scan has been recommended to evaluate mediastinal extension of this lesion2 ,8 Complete surgical excision, sparing the surrounding vital structures, remains the treatment of choice for this benign lesion. An important exception is the neonate, in whom partial excision should be performed if normal mediastinal thymic tissue cannot be radiographically identified¢ This may allow the aberrant thymic tissue to perform the required immunologic function of the normal thymus. No recurrences have been noted in children who have undergone complete excision. The differential diagnosis of a cystic neck mass in children should include branchial cleft cysts, thyroglossal duct cysts, cystic hygromas, cystic teratomas, and thyroid neoplasia. Cervical thymic cysts, although rare, should also be included, particularly in children younger than 10 years. Definitive treatment for this entity is eomplete surgical excision.
588
Otolaryngology Head and Neck Surgery April 1995
MILLER and DE VlTO
REFERENCES
1. Guba AM, Adam AE, Jacques DA, et al. Cervical presentation of thymic cysts. Am J Surg 1978;136: 430-6. 2. Nowak PA, Zarbo R J, Jacobs JR. Aberrant solid cervical thymus. Ear Nose Throat J 1988;67:670-7. 3. Tovi F~ Mares AJ. The aberrant cervical thymus-embryology, pathology, and clinical implications. Am J Surg 1978; 136:631-7. 4. Lyons TJ, Dickson JA, Variend S. Cervical thymic cysts. J Pediatr Surg 1989;24:241-3. 5. Wagner CW, Vinocur CD, Weintraub WH, Golladay ES. Respiratory complications in cervical thymic cysts. J Pediatr Surg 1988;23:657-60. 6. Zarbo R J, McClatchey KD, Areen RG, Baker SB. Thy-
7.
8. 9.
10.
11.
mopharyngeal duct cyst: a form of cervical thymus. Ann Otol Rhinol Laryngol 1983;92:284-9. Barat M, Sciubba JJ, Abramson A L Cervical thymic cyst: case report and review of literature. Laryngoscope 1985;95: 89-91. Becker GD, Ridolfi R. Cervical thymic cyst. OTOLARYNOOL HEAD NECr:SUR~ 1985;93:807-9. Spigland N, Bensoussan AL, Blanchard H, Russo P. Aberrant cervical thymus in children: three case reports and review of the literature. J Pediatr Surg 1990;25:1196-9. Moore KL. The developing human-clinically oriented embryology. 4th ed. Philadelphia: WB Saunders Co., 1988:17984. Speer FD. Thymic cysts. NY Med Coll Fower Hosp Bull 1938;1:142-50.
NOW! The F I V E - Y E A R (1986-1990) C U M U L A T I V E INDEX TO O T O L A R Y N G O L O G Y - H E A D A N D NECK S U R G E R Y can be purchased from the Publisher for $44.00. This comprehensive 104-page reference guide is a current presentation of all topics included in the Journal from January 1986 through December 1990 (volume s 9 4 - 1 0 3 ) - t h e past 10 volumes. It incorporates complete references to more than 640 original articles, abstracts, case reports, letters and editorials. It features 1668 Subject Headings, under which there are 3247 references. Each subject entry lists the complete article title, author(s), volume, page(s), and year of publication. In addition, it includes 3190 Author Entries, which list contributors, along with their respective titles, authorto-author referral, volume, page, and publication. To purchase, call or write: Mosby-Year Book, Inc., 11830 Westline Industrial Dr., St. Louis, Missouri 63146-3318, or telephone F R E E 1-800-453-4351, Subscription Services (in Missouri, call collect at 314-453-4351, Subscription Services). P R E P A Y M E N T REQ U I R E D . Make checks payable to Mosby-Year Book, Inc. (all payments must be in U.S. funds drawn on a U.S. bank). Price: $44.00 in the U.S.; $50.50 in Canada; and $48.50 in other countries (price includes mailing charges).
AVAILABLE
Cervical thymic cyst MITCHELL B. MILLER, MD, and MICHAEL A. DE VITO, MD, Albany, New York
C e r v i c a l thymic cyst is a rare congenital anomaly that may be first seen as a neck mass in children. A review of the English literature reveals 91 case reports with a variety of initial signs and symptoms.l-9 We report a patient with an asymptomatic neck mass who was found to have a cervical thymic cyst. CASE REPORT
A 5-year-old girl sought treatment for a 2-month history of an enlarging, asymptomatic, left neck mass. On physical examination, the mass measured 4 x 5 cm and was smooth, mobile, and soft. Computerized axial tomography of the neck demonstrated a 4- x 5-cm cystic mass deep to the sternocleidomastoid muscle, extending from the angle of the mandible to the level of the cricoid cartilage (Fig. 1). The lateral wall of the hypopharynx was mildly displaced by the mass. A barium swallow was normal. A preoperative diagnosis of branchial cleft cyst was made. At surgery a 4- × 5- × 5-cm soft, lobulated, cystic mass was found deep to the anterior border of the sternocleidomastoid muscle, medial to the internal jugular vein and anterior but adherent to the common carotid artery and vagus nerve. A small portion of the mass extended inferiorly to the level of the clavicle. The mass was completely excised. Pathologic examination demonstrated thymic tissue with intrathymic cyst formation containing cholesterol crystals (Fig. 2). Her postoperative course was unremarkable. DISCUSSION
The thymus originates from the third branchial pouches in the sixth week of development. Thymic tubules rapidly elongate and descend along the thymopharyngeal tracts until they fuse in the midline at
From the Division of Otolaryngology, Albany Medical College. Received for publication April 8, 1994; accepted July 8, 1994. Reprint requests: Mitchell Miller, MD, Division of Otolaryngology, A-41, Albany Medical College, Albany, NY 12208. OTOEARYNGOL~-IEADNECKSURG 1995;i12:586-8. Copyright © 1995 by the American Academy of OtolaryngologyHead and Neck Surgery Foundation, Inc. 0194-5998/95/$3.00 + 0 23/4/58968 586
Fig, t. Axial computed tomography scan demonstrating 4- x 5-cm cystic mass deep to sternocleidomastoid muscle,
8 weeks. Migration continues inferiorly until the thymus rests in the superior mediastinum at 12 weeks. 1° Thymic tissue may be present anywhere along this route of descent. Cervical thymlc cyst is a rare entity with only 92 reported cases, including out own. However, the presence of asymptomatic thymic tissue in the neck is much more common, with a reported incidence of 30% in children at autopsy, s The scarcity of clinical cases may be explained by the fact that most cervical thymic tissue remains dormant. This thymic tissue can enlarge during childhood and may be first seen as a cervical mass. In 1938 Speer 11 proposed five theories for the pathogenesis of cervical thymic cysts: (1) they may
Oto[aryngology Head and Neck Surgery Volume 'I~2 Number 4
MILLER and DE VffO
587
Fig. 2. Thymic tissue containing cholesterol crystals with intrathymic cyst formation. [Hematoxylin and eosin; original magnification × 100,1
represent remnants of branchial clefts or the thymopharyngeal tract; (2) they may result from sequestration of thymic tissue during migration; (3) they may represent neoplastic change in the lymphoid or the surrounding tissues; (4) they may result from cystic degeneration of Hassall's corpuscles; (5) they may arise from lymphoid tissue that has arrested in various stages of thymic development. Most authors 4-7agree that the arrest of migration of thymic tissue along the thymopharyngeal tracts is primarily responsible for the formation of cervical thymic cysts. Thymic cysts can be unilocular or multilocular, and they may contain clear or bloody fluid. The cyst wall may be lined with spindle-shaped columnar or cuboidal cells, with thymic tissue adjacent to the cyst. Cholesterol crystals and giant cell reaction are common. These features distinguish thymic cysts from branchial cleft cysts2 The cervical thymic cyst was present on the left side in 68% of cases, on the right side in 25%, and in the midline in 7%. Most patients (87%) had only painless swelling; however, 13% of patients had a variety of symptoms including hoarseness, dysphagia, and stridor. Respiratory distress in neonates caused by large cervical thymic cysts has been re-
ported? The average age at surgery was less than 10 years. The cysts were typically located in the anterior triangle, either anterior or deep to the sternocleidomastoid muscle. Fifty percent of thymic cysts extended into the mediastinum. A Preoperative computed tomography scan has been recommended to evaluate mediastinal extension of this lesion2 ,8 Complete surgical excision, sparing the surrounding vital structures, remains the treatment of choice for this benign lesion. An important exception is the neonate, in whom partial excision should be performed if normal mediastinal thymic tissue cannot be radiographically identified¢ This may allow the aberrant thymic tissue to perform the required immunologic function of the normal thymus. No recurrences have been noted in children who have undergone complete excision. The differential diagnosis of a cystic neck mass in children should include branchial cleft cysts, thyroglossal duct cysts, cystic hygromas, cystic teratomas, and thyroid neoplasia. Cervical thymic cysts, although rare, should also be included, particularly in children younger than 10 years. Definitive treatment for this entity is eomplete surgical excision.
588
Otolaryngology Head and Neck Surgery April 1995
MILLER and DE VlTO
REFERENCES
1. Guba AM, Adam AE, Jacques DA, et al. Cervical presentation of thymic cysts. Am J Surg 1978;136: 430-6. 2. Nowak PA, Zarbo R J, Jacobs JR. Aberrant solid cervical thymus. Ear Nose Throat J 1988;67:670-7. 3. Tovi F~ Mares AJ. The aberrant cervical thymus-embryology, pathology, and clinical implications. Am J Surg 1978; 136:631-7. 4. Lyons TJ, Dickson JA, Variend S. Cervical thymic cysts. J Pediatr Surg 1989;24:241-3. 5. Wagner CW, Vinocur CD, Weintraub WH, Golladay ES. Respiratory complications in cervical thymic cysts. J Pediatr Surg 1988;23:657-60. 6. Zarbo R J, McClatchey KD, Areen RG, Baker SB. Thy-
7.
8. 9.
10.
11.
mopharyngeal duct cyst: a form of cervical thymus. Ann Otol Rhinol Laryngol 1983;92:284-9. Barat M, Sciubba JJ, Abramson A L Cervical thymic cyst: case report and review of literature. Laryngoscope 1985;95: 89-91. Becker GD, Ridolfi R. Cervical thymic cyst. OTOLARYNOOL HEAD NECr:SUR~ 1985;93:807-9. Spigland N, Bensoussan AL, Blanchard H, Russo P. Aberrant cervical thymus in children: three case reports and review of the literature. J Pediatr Surg 1990;25:1196-9. Moore KL. The developing human-clinically oriented embryology. 4th ed. Philadelphia: WB Saunders Co., 1988:17984. Speer FD. Thymic cysts. NY Med Coll Fower Hosp Bull 1938;1:142-50.
NOW! The F I V E - Y E A R (1986-1990) C U M U L A T I V E INDEX TO O T O L A R Y N G O L O G Y - H E A D A N D NECK S U R G E R Y can be purchased from the Publisher for $44.00. This comprehensive 104-page reference guide is a current presentation of all topics included in the Journal from January 1986 through December 1990 (volume s 9 4 - 1 0 3 ) - t h e past 10 volumes. It incorporates complete references to more than 640 original articles, abstracts, case reports, letters and editorials. It features 1668 Subject Headings, under which there are 3247 references. Each subject entry lists the complete article title, author(s), volume, page(s), and year of publication. In addition, it includes 3190 Author Entries, which list contributors, along with their respective titles, authorto-author referral, volume, page, and publication. To purchase, call or write: Mosby-Year Book, Inc., 11830 Westline Industrial Dr., St. Louis, Missouri 63146-3318, or telephone F R E E 1-800-453-4351, Subscription Services (in Missouri, call collect at 314-453-4351, Subscription Services). P R E P A Y M E N T REQ U I R E D . Make checks payable to Mosby-Year Book, Inc. (all payments must be in U.S. funds drawn on a U.S. bank). Price: $44.00 in the U.S.; $50.50 in Canada; and $48.50 in other countries (price includes mailing charges).
AVAILABLE