#### Take-home messages Precursor T lymphoblastic leukaemia/lymphoblastic lymphoma is a highly aggressive disease often presenting in young adults with male predominance.1 This report describes a case of T cell acute lymphoblastic lymphoma that went into an apparent spontaneous remission with no readily identifiable cause. A 44-year-old previously fit and well Caucasian man presented with a 1-week history of shortness of breath and pleuritic chest pain. He had weight loss of 1.5 kg in the preceding 4 weeks with night sweats but no fever. There was no significant past medical history and he was not on any medication. He was a non-smoker and worked as a porter. Chest x ray (CXR) requested by his general practitioner showed a large mediastinal mass associated with right-sided pleural effusion (fig 1). This drained 1.5 l of clear, straw-coloured transudate, which contained a large number of lymphocytes and some mesothelial cells. Ultrasound-guided biopsy of the mediastinal mass showed cores of fibroadipose tissue diffusely infiltrated by relatively monomorphous, medium-sized lymphoid cells displaying rounded nuclei with inconspicuous nucleoli, scanty cytoplasm and abundant apoptosis and …