Contents lists available at ScienceDirect International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl Case Report Anatomical variations of the thymus in relation to the left brachiocephalic vein, findings of necropsia Oscar Alonso Plaza a,∗ , Freddy Moreno b a National Institute of Legal Medicine and Forensic Sciences, Cali, Colombia b Faculty of Health Sciences, Pontificia Universidad Javeriana, Cali, Colombia ARTICLE INFO Keywords: Thymus Anatomical variants Embryology Brachiocephalic vein Autopsy ABSTRACT Two cases of anatomical variations of the thymus are presented with respect to the anatomical relations with the left brachiocephalic vein and found during the necropsy process. Less than 2 days after birth with Noonan Syndrome, when the left brachiocephalic vein was scanning behind the upper thymus horns, there were other adjacent lesions consisting of three supernumerary spleens and three hepatic veins. The second case was an 8- year-old infant with child malpractice who died from urinary sepsis due to obstructive uropathy, in which case the upper lobes of the thymus were fused and formed a ring through which the left brachiocephalic vein passed. 1. Introduction The thymus (Greek, thymos) was represented by the Greeks as the place where the soul resides [1]. It consists of a bilobular primary lymphoepithelial organ located in the anterior and superior medias- tinum - caudal to the thyroid, dorsal to the sternum and ventral to the heart and the great vessels -, it has bilobed form with two superior horns that sometimes ascends to the neck. Its weight varies according to postnatal development (10g–15g), reaching its highest weight at pub- erty (30g–40g), to initiate a progressive involution with age as it is infiltrated by adipose tissue [2–4]. Histologically it is formed by a stroma that surrounds the whole organ through a capsule of irregular dense connective tissue, which is invaginated by dividing walls of the same tissue to divide the par- enchyma into irregular thymic lobules. The latter are organized on a supportive web of six epithelioreticular cell phenotypes in a superficial cortex and deep marrow of developing T-lymphocytes and associated macrophages. In this way, the function of the thymus corresponds to being the place where the T lymphocytes develop and mature [5,6]. The thymus has its embryonic origin, along with the pharynx and the thyroid and parathyroid glands, in the pharyngeal or branchial apparatus derived from the anterior primitive gut during the fifth week of intrauterine development. In this way, epithelial cells derived from the endoderm of the ventral region of the third pair of pharyngeal bags form the epithelial tubes recognized as thymic primordia, which pro- liferate towards the underlying mesenchyme in the caudal and medial sense to differentiate into the epithelial cords that originate the bran- ches Lateral as they lose connection with the pharyngeal wall. These lateral branches are the central axis of each of the thymic lobes, which merge in the midline with each other in the anterior wall of the thorax, between the posterior aspect of the sternum and the parietal serous pericardium. The endothelial epithelial cells differ- entiate the epithelial-reticular cells that constitute the supporting tissue; from the mesenchyme trapped in the parenchyma, the septa of irregular dense connective tissue and the hematopoietic stem cells of the bone marrow are formed - from the seventh week Of intrauterine development - the prelymphocytes that occupy the supporting structure to form the cortex and medulla of the thymic lobules [7–9]. Given the migration of endodermal epithelial cells during em- bryonic development for the conformation of the thymus and thyroid gland, the thymus is attached superiorly to the thyroid gland by a li- gamentous attachment, previously related to the origins of the sterno- hyoid and sternohyoid muscles and the posterior face of the sternal manubrium, and later it is related to the left brachiocephalic vein, aortic arch and its collaterals. Also, its inferior poles rest on the peri- cardium and laterally it can extend until reaching the pulmonary hilum covering the phrenic nerves [2,3]. However, this location may present a series of anatomical variations that occur during embryonic develop- ment, which present relationships with other morphological structures in the region [10–12]. In the literature, there are four types of anato- mical variants of ectopic localization commonly described, but occa- sionally the thymus can be located at the retropharyngeal level or be- hind the left brachiocephalic vein [4]. Therefore, the objective of this case report is to present two anatomical variations of the thymus with respect to the anatomical relationships with the left brachiocephalic vein, found during the necropsy process. https://doi.org/10.1016/j.ijporl.2018.01.019 Received 20 October 2017; Received in revised form 11 January 2018; Accepted 14 January 2018 ∗ Corresponding author. E-mail address: oscarplazap33@hotmail.com (O.A. Plaza). International Journal of Pediatric Otorhinolaryngology 107 (2018) 53–55 Available online 31 January 2018 0165-5876/ © 2018 Elsevier B.V. All rights reserved. T