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Ectopic cervical thymus mimicking lymph nodal metastasis in a case of papillary thyroid carcinoma


 Department of Pathology, Dayanand Medical College and Hospital, Ludhiana, Punjab, India

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Date of Submission11-May-2021
Date of Acceptance18-Dec-2021
Date of Web Publication07-Jun-2022
 


How to cite this URL:
Soni A, Narang V, Jindal S, Kaur H. Ectopic cervical thymus mimicking lymph nodal metastasis in a case of papillary thyroid carcinoma. Indian J Pathol Microbiol [Epub ahead of print] [cited 2022 Jul 2]. Available from: https://www.ijpmonline.org/preprintarticle.asp?id=346853




A 32-year-old female presented with a right-sided neck mass of one-year duration which was moving with deglutition. Ultrasonography of the neck revealed the presence of a well-circumscribed nodule in the right lobe of the thyroid measuring 2.8 × 2.5 × 1.8 centimeter along with a distinct nodule in the right neck measuring 0.8 × 0.5 × 0.5 centimeter. A possible imaging diagnosis of this being a neoplastic lesion with lymph nodal metastasis was rendered. Right hemithyroidectomy with ipsilateral neck dissection was carried out and sent for histopathological examination. Gross examination revealed a solitary grey-white lesion in the lobe of the thyroid measuring 2.5 × 2.4 × 2 centimeters. Histopathological examination revealed a tumour having histomorphological features consistent with papillary thyroid carcinoma [[Figure 1]; panel A]. All of the lymph nodes recovered from the neck dissection exhibited features of reactive hyperplasia. However, one of the sections revealed the presence of thymus tissue (composed of cortex, medulla, and Hassall corpuscles) exhibiting features of hyperplasia which were positioned alongside a parathyroid gland [[Figure 1]; panel B].
Figure 1: Photomicrograph (haematoxylin and eosin stain; ×100) shows papillary thyroid carcinoma (panel A); Photomicrograph (haematoxylin and eosin stain; ×100) shows a parathyroid gland situated next to the thymus (panel B)

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During embryological development, pharyngeal pouches are formed by evagination of pharyngeal endoderm towards the ectoderm. These pouches develop in a ventral to a dorsal sequence which is separated from each other by pharyngeal arches. Different pharyngeal pouches give rise to different craniofacial organs. Development of thymus and parathyroid glands are linked to each other which happen by ventral wing and dorsal wing of third pharyngeal pouch respectively. In the 6th week of gestation, the descent of both the inferior parathyroid gland and thymus happens with the positioning of the parathyroid gland close to the inferior thyroid pole and thymus into the mediastinum. Any maldescent during the process of migration may lead to the development of the ectopic thymus or ectopic parathyroid gland and infrequently both. The ectopic site can be anywhere on the path of migration from the angle of the mandible to the superior mediastinum.[1] The ectopic thymus commonly occurs in the neck, at the level of the thyroid gland. However, uncommonly it involves other sites such as the base of the skull, posterior aortic arch, middle ear, submandibular gland, and tonsil.[2] The ectopic cervical thymus is also seldom diagnosed preoperatively because of its rarity and asymptomatic behavior. It is rare in patients older than twenty years and is mostly detected incidentally in patients operated on for any neck mass.[3] The ectopic cervical thymus may sometimes be of considerable size causing a clinically palpable lesion other than the primary thyroid nodule posing a clinical suspicion of lymph nodal metastasis. It leads to an unnecessary radical neck dissection, as was noted in our case too. Very infrequently ectopic thymus may harbor any of the thymic neoplasms. Thus we emphasize that although rare, the probability of ectopic thymus should always be considered preoperatively while analyzing suspected thyroidal neoplastic lesion with an additional neck mass. An intra-operative consultation may help in such cases to avoid a radical neck dissection. This case brings an insight into the basis of embryological defect responsible for ectopic thymus and/or parathyroid and its clinical implication.

Ethical approval

Ethical clearance has been taken from hospital ethical committee.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Durmaz E, Barsal E, Parlak M, Gurer I, Karaguzel G, Akcurin S, et al. Intrathyroidal ectopic thymic tissue may mimic thyroid cancer: A case report. J Pediatr Endocrinol Metab 2012;25:997-1000.  Back to cited text no. 1
    
2.
Bale PM, Sotelo-Avila C. Maldescent of the thymus: 34 necropsy and 10 surgical cases, including 7 thymuses medial to the mandible. Pediatr Pathol 1993;13:181-90.  Back to cited text no. 2
    
3.
Prasad TR, Chui CH, Ong CL, Meenakshi A. Cervical ectopic thymus in an infant. Singapore Med J 2006;47:68-70.  Back to cited text no. 3
    

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Correspondence Address:
Ankita Soni,
Department of Pathology, Dayanand Medical College and Hospital, Tagore Nagar, Ludhiana - 141001, Punjab
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_466_21



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