Intrapulmonary schwannoma mimicking metastatic papillary thyroid carcinoma: a case report with literature review

Schwannomas are tumours that arise from differentiated Schwann cells and are typically benign. Intra-thoracic site as a location for schwannomas is extremely rare, and if present, the posterior mediastinum serves as the preferred anatomic site. Amongst the pulmonary neoplasms, schwannomas arising in the lung parenchyma are even rarer, and only a handful of case reports have described this rare nerve sheath tumour as intrapulmonary origin. Considering the rarity, Schwannoma as a differential diagnosis in a patient with an intrapulmonary lesion is rarely considered clinico-radiologically. A review of pulmonary schwannomas from 1983 to 2025 was carried out, highlighting significant clinical aspect of this rare neoplasm at an unusual site. We report a case of a 50-year-old female who presented with a midline neck swelling that moves with deglutition. Fine needle aspiration cytology from the swelling was suggestive of Papillary thyroid carcinoma. Contrast-enhanced computed Tomography of the Neck and Thorax revealed a large sized, solid enhancing lesion, with heterogeneous enhancement measuring 8.3 × 5.8 × 6.6 cm along the left lower lobe of the lung, favouring metastasis. A clinico-radiological diagnosis of papillary thyroid carcinoma with lung metastasis was considered. However, ultrasound-guided core biopsy of the mass revealed a benign spindle cell lesion confirmed by immunohistochemistry findings. The mass was surgically resected, and histomorphology, aided by immunohistochemistry positivity for S-100 and SOX 10, confirmed the diagnosis of Intrapulmonary Schwannoma. The patient was asymptomatic 2-months post surgery. The case report highlights a rare instance of a benign pulmonary neoplasm masquerading as metastasis in a patient with Papillary Thyroid Carcinoma. Timely recognition of such synchronous neoplasms is crucial, given their distinct therapeutic and prognostic implications. Also, the concurrent review highlights various clinical aspects of intrapulmonary schwannoma, adding valuable insights into a rare neoplasm at an unusual site.