Clear Cell Carcinoma of the Thymus: An Improbable Enemy

Introduction Thymic clear cell carcinoma is the most uncommon subtype of thymic carcinoma, with 20 cases reported worldwide. Case description We present the case of a 61-year-old female with dyspnoea and chest pain for 2 days. Computed tomography (CT) angiography showed pulmonary thromboembolism and the existence of mediastinal and bilateral hilar lymphadenopathy, the largest infracarinal with an inferior axis of 25 mm, and also, micronodules on the left pulmonary parenchyma. The patient was admitted for aetiological assessment and underwent anticoagulant therapy. After a month, she had an ischaemic stroke, the sequelae of which proved to be fatal. The autopsy showed a mass in the superior-anterior mediastinum, with dimensions of 11×8×6 cm, corresponding to a thymus signet ring cell primary carcinoma. The immunohistochemistry study revealed that this mass was positive for AE1/AE3, CK5/6 and CK7. Conclusion The clinical, morphological and immunophenotypic diversity of this tumour makes its diagnosis a difficult multidisciplinary challenge, which requires a high level of clinical knowledge and accurate imaging and histological investigation. Learning points Thymic clear cell carcinoma is a very rare entity with an aggressive and nonspecific clinical behaviour.There are no defined diagnostic criteria, although diagnosis could be established with histologic/cytology analysis.There are no clear guidelines for treatment, which can include highly invasive surgery and chemotherapy or radiation therapy.