The mediastinum is in the central part of the thoracic cavity and contains many vital organs, such as the heart, trachea, thymus, esophagus, etc. The structure of the mediastinum can be divided into three compartments, namely, the anterior, middle, and posterior mediastinum, from which various types of tumours may originate. [1,2]. Tumours arising from the mediastinum are rare in children and adolescents, and most such tumours are malignant.

For instance, thymomas and lymphomas can arise from the anterior mediastinum. Germ cell tumors mainly arise from the middle mediastinum, while neurogenic tumors often originate from the sympathetic nerve chains or spinal roots of the posterior mediastinum [3]. In children, Lymphoma is the most common primary anterior mediastinal tumor. Germ cell neoplasms are the second most prevalent tumor, followed by thymic lesions and mesenchymal tumors. In children, thymic abnormalities consist primarily of hyperplasia and cysts.

A 10-year-old boy second issue of non-consanguineous marriage presented to the casualty with complaints of difficulty in breathing and altered mentation for the past couple of hours.

History of similar complaints four months back. He was diagnosed with bronchial asthma with lower respiratory tract infection and was treated for the same. The child had minimal relief with the ongoing treatment—no history of bronchial asthma or allergies in the family. On examination child was toxic looking, GCS 8/15, with features of hypovolemic shock, had severe pallor and pedal edema. On cardiovascular examination, the patient had gallop rhythm. On respiratory system examination trachea was shifted to the left side and had a silent chest on auscultation.

The child was admitted to PICU, and attempts were made for hemodynamic stabilization was child put on mechanical ventilator support. Within 48 hours of stay in PICU child had multiple fever spikes, one episode of Generalized Tonic-clonic convulsion for which adequate treatment was started. The child had a bout of desaturation when high-quality CPR was started but could not be revived.

Even the shape of the thymus changes with age where it is known to be quadrilateral shaped with convex margins at around five years of age and changes to triangular shape with straight margins by the age of 15 years [5]. Thymic lesions form approximately 2% of all mediastinal tumours in children [6]. The clinical profile of these patients varies from asymptomatic incidentally detected masses to being symptomatic with dyspnoea, dysphagia or venous congestion [8]. The myriad paraneoplastic syndromes (PNS) associated with the thymus, such as myasthenia gravis (MG), pure red cell aplasia, hypogammaglobulinemia, pemphigus, Sjogren's syndrome, manifest more commonly in adults rather than in childhood [1,7]. Besides the ones mentioned above, other clinical manifestations include gastrointestinal disorders (chronic ulcerative colitis), collagen and autoimmune disorders (scleroderma and polymyositis), dermatologic disorders (alopecia), endocrine disorders (Cushing's syndrome), renal disease (nephrosis) and hematologic syndromes (agranulocytosis) [7]. It has also been seen that MG is the most common PNS and is generally seen commonly in children <10 years of age [8].

Radiological classification Radiologists have attempted to classify thymic lesions in children according to the density of the visible mass into solid, fatty and cystic lesions. An ordinary differential of a solid thymic mass in a child is a prominent normal thymus which is also referred to as a "pseudomass" since it isn't a tumor but the normal appearance of the thymus in that particular age group [5]. The other solid lesions are ectopic thymus, retrocaval (between the superior vena cava and the great arteries) or cervical, thymic hyperplasia or thymic neoplasms. The cystic lesions include thymic cysts, and fatty lesions are the thymolipomas.

The other method by which radiologists have classified paediatric thymic lesions is based on the size of the thymus, whether it is small or large [9]. Small thymus can be physiological, which may be age-related involutions or treatment-related atrophy or immunodeficiency disorders leading to hypoplasia or aplasia. The large thymus included hyperplasias and neoplastic lesions. Thymic hyperplasia can be true thymic hyperplasia or lymphoid (follicular) hyperplasia. True thymic hyperplasias result in a change in the shape of the gland and an increase in the size, which may be more than 50% of the original.

Thymomas are extremely rare in children forming less than 5% of all mediastinal masses. They are usually asymptomatic and are detected incidentally on routine chest radiography. Thymic carcinomas are sporadic tumors in adults and are even rarer in the paediatric age group forming less than 1% of all childhood neoplasms [16,17]. The thymic carcinomas arise from the thymic epithelial cells, which lose their functional and phenotypic features and appear anaplastic [6]. Thymic carcinoids are also rare, with an incidence of 2.6–8% [18]. They are exclusively found in males. These carcinoids are known to have increased morbidity with local spread, distant metastasis and recurrence.

Thymic Lymphoma forms the most common anterior mediastinal mass in children, and thymic involvement by lymphomas can occur commonly in disseminated disease compared to primary thymic origin. Among the histopathological subtypes, Hodgkin lymphoma forms the most common variant [14].

This case shows the importance of evaluating any infant or child presenting with recurrent wheezing for anterior mediastinal mass. Suspicion on initial presentation is a must as the prognosis and survival rates are highly dependent on early diagnosis and treatment.