A 36 year-old non-smoker woman was admitted because of a rapidly growing mass at the left hilum. Fiberoptic bronchoscopy did not show any abnormality. A percutaneous Rotex needle biopsy and a cutting needle biopsy showed atypical cells suggestive of an anaplastic tumor, possibly a sarcoma. A thoracotomy biopsy demonstrated nodal and pulmonary involvement by Hodgkin lymphoma (nodular-sclerosis form) and pulmonary TBC (granulomas with caseum and acid fast bacilli (AFB)). The patient started treatment with isoniazid, rifampin and pirazynamide and then she received chemotherapy and radiotherapy. One year later her chest and abdominal CT were normal. Twelve months after that she developed severe dyspnea with a chest x-ray film with interstitial infiltrates and a mass at the left-hilum. She worsened quickly and died. At autopsy no evidence of active TBC was found and extensive involvement by lymphoma was demonstrated. The diagnosis in this patient was not obtained by clinical-radiological signs or by non-invasive tests but only by surgical biopsy. The association between neoplasm and TBC is well known, but now is very rare. In Argentina TBC prevalence in lymphomas is 1.2% (higher than control population). TBC diagnosis can occasionally be difficult. In most of undiagnosed patients TBC is the main contributor to death. In this patient the mediastinopulmonary mass was adequately diagnosed only after an open biopsy which showed it to be caused by two coexistent diseases, previously unsuspected and both amenable of effective treatment. This case shows the heterogeneity of TBC presentation and stresses the need to consider it in each non-defined mediastino-pulmonary lesion in countries where TBC is highly prevalent.(ABSTRACT TRUNCATED AT 250 WORDS)