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An 11-day-old boy with 22q11.2 deletion syndrome, tetralogy of Fallot, and unilateral renal agenesis presented with a right neck mass and intermittent inspiratory stridor present at birth. The patient did not require positive pressure or intubation, but he had intermittent stridor associated with desaturations. He had feeding difficulty and failure to thrive. On physical examination, the newborn had facial dysmorphism, including a broad and flat nasal dorsum and mild micrognathia. Flexible fiberoptic laryngoscopy revealed a cystic lesion consistent with a vallecular cyst. A modified barium swallow study demonstrated laryngeal penetration and aspiration of thin and nectar-thick liquids. A diffuse, soft, palpable mass was present along the right neck.
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C. Ectopic thymus
The biopsy results of the mass in this newborn with 22q11.2 deletion syndrome were consistent with ectopic thymic tissue. Cytopathologic findings demonstrated features consistent with normal thymic tissue: a polymorphic population of lymphocytes, fibroadipose tissue, and Hassall corpuscles (eosinophilic concentric islands of squamous cells with central keratinization). A cervical ectopic thymus is typically located deep within the neck and is not palpable; these lesions are commonly incidental and asymptomatic. The infant’s palpable neck mass was therefore an unusual presentation of an ectopic thymus, although this presentation has been documented in case reports.1,2
In an infant, ectopic thymus usually appears similar to normal thymus tissue in terms of imaging characteristics, with a mildly hyperintense signal relative to muscle on T1-weighted and T2-weighted images. When there is a mediastinal thymus, continuity can usually be demonstrated by MRI; the diagnosis is often made without the need for a biopsy. However, this patient had no mediastinal thymic tissue. Low apparent diffusion coefficient values have been described with ectopic thymus tissue,1,2 but the degree to which diffusion restriction can be seen with malignant processes and convex masslike features prompted us to perform a fine-needle aspiration of the neck mass during the vallecular cyst excision.
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Corresponding Author: Alexandra O. Hamberis, BS, Department of Otolaryngology, Medical University of South Carolina, 135 Rutledge Ave, MSC 550, Charleston, SC 29425 (firstname.lastname@example.org).
Published Online: October 3, 2019. doi:10.1001/jamaoto.2019.2803
Conflict of Interest Disclosures: None reported.
Additional Contributions: We thank the patient’s family for granting permission to publish this information. We also would like to thank Olga Chajewski, MD, Department of Pathology and Laboratory Medicine, Medical University of South Carolina, and Milad Yazdani, MD, Department of Radiology and Radiological Science, Medical University of South Carolina, for their review of the pathology and imaging for this article.
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