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Radiology Quiz Case 2: Diagnosis

Radiology Quiz Case 2: Diagnosis Diagnosis: Ectopic thymus The mass, which was approximately 6 cm in diameter, was removed without difficulty. It did not appear to be cystic or vascular, but it felt soft and compressible to palpation. The histopathologic features are shown in Figure 4. Figure 4. View LargeDownload The thymus gland is a primary lymphoid organ that is located in the anterosuperior part of the mediastinum and the lower aspect of the neck. The thymic stroma arises primarily from the third pharyngeal pouch, with a minor contribution from the fourth pharyngeal pouch during the fourth to sixth week of fetal development.1 Thymic primordia from the left and right migrate caudally and fuse in the midline inferior to the thyroid gland to form a single thymus gland at approximately the seventh week.1 The thymopharyngeal tract subsequently involutes.1 Failure to maintain a normal rate of descent, sequestration, or persistence of thymic rests along the pathway can lead to associated abnormalities.1 The thymus is necessary in early life for the normal development of immunologic function. It reaches its greatest relative weight shortly after birth and its greatest absolute weight at puberty.1 By adulthood, it involutes and has been largely replaced by adipose tissue.1 The pathogenesis of the ectopic thymus is believed to be from the defective pathway of the embryological descent of the thymus. Therefore, thymic anomalies can be detected at any level of the pathway of descent, from the angle of the mandible to the superior mediastinum or as far inferior as the diaphragm. A case of an ectopic thymus in the retropharyngeal region has been reported in the literature.2 Curé et al3 reported 2 cases of ectopic cervical thymus, but, unlike ours, which was solid and homogeneous, both cases had cystic elements on the magnetic resonance images. Ectopic thymus usually looks like normal thymic tissue on microscopic examination.4 Some authors have reported that ectopic thymus seems to have a male preponderance and occurs more commonly on the left side; however, others have not found such predelictions.5 Cervical ectopic thymus is rarely symptomatic.6 Only 6% to 10% of patients with cervical ectopic thymus present with neck pain, stridor, dyspnea, dysphagia, and/or hoarseness.6 Usually, patients experience these symptoms after minor trauma, vaccination, or an upper respiratory tract infection that results in rapid enlargement of the mass.7 A detailed history and physical examination can often help to narrow the differential diagnosis considerably. However, it is difficult to diagnose this entity before surgery because of its rarity. Ultrasonography is a noninvasive and cost-effective imaging modality that can help the physician to further delineate the character of the mass. Computed tomography with contrast is useful in identifying nearby vital structures, bony landmarks, and the cystic nature of the mass. It typically demonstrates a homogeneous, nonenhancing mass anterior to the sternocleidomastoid muscle.6 Magnetic resonance imaging is the most accurate, noninvasive method with which to identify a cervical lesion without exposing the patient to unnecessary radiation. The lesion will appear as slightly more intense than muscle on T1-weighted images and isointense compared with adipose tissue on T2-weighted images.8 Several published articles have shown that fine-needle aspiration can be used to obtain a tissue diagnosis, with good results.9 However, the data are sparse concerning fine-needle aspiration's sensitivity and specificity of thymic tissue in children.4 Surgical excision is the procedure of choice for definitive diagnosis and treatment in most pediatric neck masses, including cervical thymic lesions.6 A review of the literature shows that complete removal can provide an excellent prognosis and no episodes of recurrence.6 Before surgical excision, if thymic tissue is suspected, it is helpful to perform preoperative imaging to confirm the presence of a mediastinal thymus. A small study implied that thymectomy in infants younger than 3 months did not cause lymphocytopenia but did cause a reduction in the T-cell count and T-cell subsets.10 Our patient presented with a rapidly growing neck mass, with early stages of airway compression on imaging, necessitating prompt surgical intervention. He did not have a mediastinal thymus but developed a thymic shadow during the course of his follow-up. He showed no clinical signs of immunodeficiency, despite having a mildly decreased preoperative T-cell count. He is being followed up by our otolaryngology department and immunology service to monitor for any signs of immunocompromise. Return to Quiz Case 2. Box Section Ref ID Submissions Residents and fellows in otolaryngology are invited to submit quiz cases for this section and to write letters to the Archives commenting on cases presented. Quiz cases should follow the patterns established. See Instructions for Authors (http://archotol.ama-assn.org/misc/ifora.dtl). Material for CLINICAL PROBLEM SOLVING: RADIOLOGY should be submitted electronically via the online submission and review system at http://manuscripts.archoto.com. Reprints are not available from the authors. References 1. Van De Water TRStaecker H Otolaryngology: Basic Science and Clinical Review. New York, NY Thieme-Stratton Inc2006; 2. Shah SSLai SYRuchelli EKazahaya KMahboubi S Retropharyngeal aberrant thymus. Pediatrics 2001;108 (5) E94PubMedGoogle ScholarCrossref 3. Curé JKTagge EPRichardson MSMulvihill DM MR of cystic aberrant cervical thymus. AJNR Am J Neuroradiol 1995;16 (5) 1124- 1127PubMedGoogle Scholar 4. He YZhang ZYZhu HGGuo WWang LZ Infant ectopic cervical thymus in submandibular region. Int J Oral Maxillofac Surg 2008;37 (2) 186- 189PubMedGoogle ScholarCrossref 5. Nowak PAZarbo RJJacobs JR Aberrent solid cervical thymus. Ear Nose Throat J 1988;67 (9) 670, 673, 676- 677PubMedGoogle Scholar 6. Scott KJSchroeder AAGreinwald JH Jr Ectopic cervical thymus: an uncommon diagnosis in the evaluation of pediatric neck masses. Arch Otolaryngol Head Neck Surg 2002;128 (6) 714- 717PubMedGoogle ScholarCrossref 7. Kacker AApril MMarkentel CBBreuer F Ectopic thymus presenting as a solid submandibular neck mass in an infant: case report and review of literature. Int J Pediatr Otorhinolaryngol 1999;49 (3) 241- 245PubMedGoogle ScholarCrossref 8. Prasad TRChui CHOng CLMeenakshi A Cervical ectopic thymus in an infant. Singapore Med J 2006;47 (1) 68- 70PubMedGoogle Scholar 9. Tunkel DEErozan YSWeir EG Ectopic cervical thymic tissue: diagnosis by fine needle aspiration. Arch Pathol Lab Med 2001;125 (2) 278- 281PubMedGoogle Scholar 10. Brearley SGentle TABaynham MIRoberts KDAbrams LDThompson RA Immunodeficiency following neonatal thymectomy in man. Clin Exp Immunol 1987;70 (2) 322- 327PubMedGoogle Scholar http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Otolaryngology - Head & Neck Surgery American Medical Association

Radiology Quiz Case 2: Diagnosis

Archives of Otolaryngology - Head & Neck Surgery , Volume 137 (2) – Feb 21, 2011

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References (10)

Publisher
American Medical Association
Copyright
Copyright © 2011 American Medical Association. All Rights Reserved.
ISSN
0886-4470
eISSN
1538-361X
DOI
10.1001/archoto.2011.5-b
Publisher site
See Article on Publisher Site

Abstract

Diagnosis: Ectopic thymus The mass, which was approximately 6 cm in diameter, was removed without difficulty. It did not appear to be cystic or vascular, but it felt soft and compressible to palpation. The histopathologic features are shown in Figure 4. Figure 4. View LargeDownload The thymus gland is a primary lymphoid organ that is located in the anterosuperior part of the mediastinum and the lower aspect of the neck. The thymic stroma arises primarily from the third pharyngeal pouch, with a minor contribution from the fourth pharyngeal pouch during the fourth to sixth week of fetal development.1 Thymic primordia from the left and right migrate caudally and fuse in the midline inferior to the thyroid gland to form a single thymus gland at approximately the seventh week.1 The thymopharyngeal tract subsequently involutes.1 Failure to maintain a normal rate of descent, sequestration, or persistence of thymic rests along the pathway can lead to associated abnormalities.1 The thymus is necessary in early life for the normal development of immunologic function. It reaches its greatest relative weight shortly after birth and its greatest absolute weight at puberty.1 By adulthood, it involutes and has been largely replaced by adipose tissue.1 The pathogenesis of the ectopic thymus is believed to be from the defective pathway of the embryological descent of the thymus. Therefore, thymic anomalies can be detected at any level of the pathway of descent, from the angle of the mandible to the superior mediastinum or as far inferior as the diaphragm. A case of an ectopic thymus in the retropharyngeal region has been reported in the literature.2 Curé et al3 reported 2 cases of ectopic cervical thymus, but, unlike ours, which was solid and homogeneous, both cases had cystic elements on the magnetic resonance images. Ectopic thymus usually looks like normal thymic tissue on microscopic examination.4 Some authors have reported that ectopic thymus seems to have a male preponderance and occurs more commonly on the left side; however, others have not found such predelictions.5 Cervical ectopic thymus is rarely symptomatic.6 Only 6% to 10% of patients with cervical ectopic thymus present with neck pain, stridor, dyspnea, dysphagia, and/or hoarseness.6 Usually, patients experience these symptoms after minor trauma, vaccination, or an upper respiratory tract infection that results in rapid enlargement of the mass.7 A detailed history and physical examination can often help to narrow the differential diagnosis considerably. However, it is difficult to diagnose this entity before surgery because of its rarity. Ultrasonography is a noninvasive and cost-effective imaging modality that can help the physician to further delineate the character of the mass. Computed tomography with contrast is useful in identifying nearby vital structures, bony landmarks, and the cystic nature of the mass. It typically demonstrates a homogeneous, nonenhancing mass anterior to the sternocleidomastoid muscle.6 Magnetic resonance imaging is the most accurate, noninvasive method with which to identify a cervical lesion without exposing the patient to unnecessary radiation. The lesion will appear as slightly more intense than muscle on T1-weighted images and isointense compared with adipose tissue on T2-weighted images.8 Several published articles have shown that fine-needle aspiration can be used to obtain a tissue diagnosis, with good results.9 However, the data are sparse concerning fine-needle aspiration's sensitivity and specificity of thymic tissue in children.4 Surgical excision is the procedure of choice for definitive diagnosis and treatment in most pediatric neck masses, including cervical thymic lesions.6 A review of the literature shows that complete removal can provide an excellent prognosis and no episodes of recurrence.6 Before surgical excision, if thymic tissue is suspected, it is helpful to perform preoperative imaging to confirm the presence of a mediastinal thymus. A small study implied that thymectomy in infants younger than 3 months did not cause lymphocytopenia but did cause a reduction in the T-cell count and T-cell subsets.10 Our patient presented with a rapidly growing neck mass, with early stages of airway compression on imaging, necessitating prompt surgical intervention. He did not have a mediastinal thymus but developed a thymic shadow during the course of his follow-up. He showed no clinical signs of immunodeficiency, despite having a mildly decreased preoperative T-cell count. He is being followed up by our otolaryngology department and immunology service to monitor for any signs of immunocompromise. Return to Quiz Case 2. Box Section Ref ID Submissions Residents and fellows in otolaryngology are invited to submit quiz cases for this section and to write letters to the Archives commenting on cases presented. Quiz cases should follow the patterns established. See Instructions for Authors (http://archotol.ama-assn.org/misc/ifora.dtl). Material for CLINICAL PROBLEM SOLVING: RADIOLOGY should be submitted electronically via the online submission and review system at http://manuscripts.archoto.com. Reprints are not available from the authors. References 1. Van De Water TRStaecker H Otolaryngology: Basic Science and Clinical Review. New York, NY Thieme-Stratton Inc2006; 2. Shah SSLai SYRuchelli EKazahaya KMahboubi S Retropharyngeal aberrant thymus. Pediatrics 2001;108 (5) E94PubMedGoogle ScholarCrossref 3. Curé JKTagge EPRichardson MSMulvihill DM MR of cystic aberrant cervical thymus. AJNR Am J Neuroradiol 1995;16 (5) 1124- 1127PubMedGoogle Scholar 4. He YZhang ZYZhu HGGuo WWang LZ Infant ectopic cervical thymus in submandibular region. Int J Oral Maxillofac Surg 2008;37 (2) 186- 189PubMedGoogle ScholarCrossref 5. Nowak PAZarbo RJJacobs JR Aberrent solid cervical thymus. Ear Nose Throat J 1988;67 (9) 670, 673, 676- 677PubMedGoogle Scholar 6. Scott KJSchroeder AAGreinwald JH Jr Ectopic cervical thymus: an uncommon diagnosis in the evaluation of pediatric neck masses. Arch Otolaryngol Head Neck Surg 2002;128 (6) 714- 717PubMedGoogle ScholarCrossref 7. Kacker AApril MMarkentel CBBreuer F Ectopic thymus presenting as a solid submandibular neck mass in an infant: case report and review of literature. Int J Pediatr Otorhinolaryngol 1999;49 (3) 241- 245PubMedGoogle ScholarCrossref 8. Prasad TRChui CHOng CLMeenakshi A Cervical ectopic thymus in an infant. Singapore Med J 2006;47 (1) 68- 70PubMedGoogle Scholar 9. Tunkel DEErozan YSWeir EG Ectopic cervical thymic tissue: diagnosis by fine needle aspiration. Arch Pathol Lab Med 2001;125 (2) 278- 281PubMedGoogle Scholar 10. Brearley SGentle TABaynham MIRoberts KDAbrams LDThompson RA Immunodeficiency following neonatal thymectomy in man. Clin Exp Immunol 1987;70 (2) 322- 327PubMedGoogle Scholar

Journal

Archives of Otolaryngology - Head & Neck SurgeryAmerican Medical Association

Published: Feb 21, 2011

Keywords: diagnostic radiologic examination,radiology specialty

There are no references for this article.