We point out the issue of differential diagnosis regarding the finding of ectopically localised thymic tissue (a thymic cyst) in the neck. Thymic tissue can be found anywhere along its developmental tract of descent, from the angle of the mandible to the upper mediastinum. Disruption of the thymic descent can result in ectopically/abnormally localised islets of accessory thymic tissue, which may undergo cystic changes, as described in a case report by Sun et al. This anatomical variation of the thymus may be clinically misinterpreted as a neoplasm or other congenital anomalies as a branchial cyst, lymphatic malformation or cystic hygroma. The present editorial focuses on the challenge of establishing a diagnosis of ectopically localised tissue of thymus often presented as a lateral cervical mass, especially in the case of cystic variation/degeneration of this thymic tissue. We summarise hypotheses on the origin of such congenital cervical thymic cysts from the point of view of evolutionary history and embryology. We also discuss lesser-known facts about the anatomy, histopathology and developmental biology of the thymus as one of the most enigmatic organs in the human body.

Introduction: Cervical thymic cyst accounts for (0.3-1) % of cervical cysts in children and are usually present during the first decade of life with few reported cases in adults. Herein, we present a 34-year-old female with a cervical thymic cyst. We conducted a review of all the previously reported cases as well. Case presentation: The patient complained of an anterolateral neck swelling that was noticed one year ago. It was a soft, fluctuant, mobile, non-tender swelling in the midline and the right side of the lower neck. Neck ultrasonography revealed a large thin-walled cyst, with no internal septa, echoes, or solid parts. Post-contrast MRI of the neck showed a well-defined, oblong-shaped, lobulated cystic lesion just beneath the strap muscle. The cyst extended caudally to the superior border of the anterior mediastinum at the level of the upper border of the manubrium sterni. The patient underwent excision of the swelling under general anesthesia via Kocher's collar neck incision. Connection with the thymus gland was detected behind the manubrium sterni which was separated. Pathological examination showed prominent thymic tissue confirming the diagnosis of a cervical thymic cyst. Conclusion: Adult cervical thymic cyst is very rare with a few cases reported in the literature. Surgical excision in symptomatic patients is the treatment of choice. Paper's main novel aspects: • A rare presentation of a cervical thymic cyst in an adult. • A comprehensive literature review including all the previously reported cases in one table.

Thymic cysts are rare benign neck masses, accounting for less than 1% of all cervical masses. This study aims to discern different presentations, investigations, and treatment options of thymic cysts in adults by reviewing prior published studies from January 2010 to October 2021 to bridge the knowledge gap since the last review by Michalopoulos in 2011. Moreover, we present a case of a 28-year-old male with a left cervical thymic cyst.

Data were obtained from a literature search using the ScienceDirect, PubMed, ResearchGate, and Google Scholar databases.

This study retrospectively analyzes reported cases of adult cervical thymic cysts by collecting demographic data, patient presentation, duration, location, size, type of imaging, fine-needle aspiration, and surgical approach. Eighteen patients were included. Cysts were seen on the left (n = 9), right (n = 5), and midline (n = 4). The age of the patients ranged from 19 to 64 years. Most patients present with painless left-sided neck swelling. Computed tomography (CT) was the preferred imaging modality in most cases. Moreover, surgical excision was essential for therapeutic and diagnostic purposes. This study did not require institutional review board approval.

Adult cervical thymic cyst is a rare etiology. Nevertheless, a painless left-sided neck mass with no clear lower border should uphold thymic cyst as a differential diagnosis. MRI and CT scans are the preferred imaging modalities for preoperative planning. Surgical excision is mandatory for treatment and histological confirmation. As of October 2021, around 54 cases of adult thymus cysts had been reported to the best of our knowledge and review.

Cervical thymic cysts (CTCs) represent 1% of all cervical cystic masses. A review of the literature found that CTCs are typically asymptomatic, with a propensity to be left sided. CTCs often require histological evaluation for diagnosis. A 27-year-old male patient presented to an outpatient otolaryngology clinic with worsening bilateral jaw and neck pain and an incidental right-sided neck mass found on cervical MRI. Preoperative differential diagnosis included venolymphatic malformation versus branchial cleft cyst. Histological examination of the excised specimen provided diagnosis of a CTC. Postoperatively, the patient reported improvement in cervical pain. CTCs are a rare cause of lateral neck mass in young adults. Typical presentation included neck enlargement with no symptoms or in some cases compressive symptoms. It is important to consider CTCs when formulating a differential for a lateral neck mass.

Cervical thymic cyst is rare lesions leading to cervical mass. As it is a rare entity, it might be confused with other congenital neck masses or neoplastic lesions. Preoperative diagnosis is almost impossible. In the present study, a patient who was operated with prediagnosis of branchial cyst and diagnosed with thymic cyst according to the histopathologic examination was presented. A 16-month-old girl was admitted to our clinic with the complaint of growing right neck mass that was realized about 4 months ago. Magnetic resonance imaging (MRI) of the neck demonstrated a rim-enhanced hypointense cystic lesion in the posterior aspect of the submandibular gland, without tracheal right lateral and mid plane on MRI, curving common carotid artery to the medial. Patients underwent surgery under general anesthesia in company with existing findings. Hypoglossal nerve was surrounded by the mass, and the mass was totally resected. The final pathology result was reported as thymic cyst. Cervical thymic masses might be unnoticed in the differential diagnosis of the cervical mass as they are rarely seen entities. Histopathologic examination of the thymus tissue was performed for diagnosis. Surgical excision is the ideal treatment approach and no postoperative recurrence has been reported.