An 11-year-old male presented with worsening respiratory symptoms for two weeks, weight loss, and cervical lymphadenopathy. His past medical history included asthma and severe atopic dermatitis, which at presentation were inadequately controlled. Clinical examination revealed hypoxaemia (oxygen saturation <92% in room air), respiratory distress and enlarged non-tender cervical lymphadenopathy. The chest roentgenogram showed bilateral diffuse micronodular opacities (Fig. 1). The leading diagnostic consideration at this point was miliary tuberculosis given the high prevalence of tuberculosis in our region. However, thorough microbiological investigation, including mycobacterial culture and polymerase chain reaction (PCR) failed to demonstrate Mycobacterium tuberculosis.
Tissue was obtained from one of the enlarged cervical lymph nodes to investigate the possibility of lymphoma. Histopathology of the core biopsy showed focal involvement by metastatic carcinoma demonstrating papillary-cystic growth with scattered solid islands and psammoma bodies (Fig. 2). The neoplastic cells displayed nuclear enlargement with irregular nuclear membranes, nuclear overlap and "Orphan Annie eye" nuclear inclusions. Immunohistochemical interrogation revealed positivity with cytokeratin (CK) 7, thyroid transcription factor 1 (Fig. 3), and thyroglobulin. These findings supported the pathological diagnosis of metastatic PTC.
Retrospectively, further clinical examination revealed an ill-defined 2,5 x 1,5 cm left thyroid nodule. Ultrasonography confirmed a heterogeneous left thyroid nodule with internal calcifications. Considering the histological diagnosis, the chest roentgenogram findings were reviewed to now include carcinomatosis of the lung. Uncontrasted magnetic resonance imaging (MRI) of the mediastinum and neck revealed a lobulated, predominantly solid thyroid mass that returned heterogeneous T2 high signal and T1 low signal, with associated extensive bilateral cervical lymphadenopathy. Preoperative thyroid scintigraphy was not performed due to local unavailability of radioactive iodine during the Covid19 pandemic. Total thyroidectomy with central and modified left cervical lymph node dissection was performed, preserving the sternocleidomastoid muscle, accessory nerve and internal jugular vein, and removing nodes from zones 2-6. Surgical findings revealed a firm, ill-defined mass involving the left lobe of the thyroid, invading the strap muscles. Multiple pathological lymph nodes were noted in both the central and the left lateral compartments of the neck. Pathological evaluation of the resection specimen revealed extensive multifocal involvement by PTC, with extrathyroidal extension and widespread involvement of cervical lymph nodes. Seven out of 9 nodes in the central compartment were positive, and 15 out of 59 nodes were positive in the lateral compartment. Immunohistochemistry for BRAFV600E was negative.
Postoperative calcium-phosphate metabolism was normal, and the patient did not experience any further adverse events. The postoperative thyroid hormone status was as follows: thyroid stimulating hormone (TSH) 16.47 mU/L (normal range 0.57-4.03), thyroxine (T4) 9.0 pmol/L (8.5-13.6), thyroglobulin 4081.0 ug/L (normal range 3.5-77.0) and antithyroglobulin 15 (normal <115 U/mL). Postoperative levothyroxine was initiated because of the hiatus in receiving radioactive iodine therapy for the metastatic lung disease. Prior to initiation of thyroid hormone replacement, a whole-body diagnostic I-131 scan revealed extensive uptake of iodine in the lungs bilaterally. This finding confirmed the preoperative impression of widespread pulmonary metastases. The patient was discharged from hospital pending the first course of therapeutic radioactive iodine (RAI) to treat the metastatic lung disease.