title: Unsuspected Pneumocystis pneumonia in an HIV-seronegative patient with untreated lung cancer: circa case report.
abstract: BACKGROUND
  Patients with solid malignant tumours are at increased risk of Pneumocystis jiroveci infection from immunosuppression as a result of chemotherapy and/or radiotherapy, but active Pneumocystis pneumonia (PCP) in untreated lung cancer is uncommon.
  
  
  METHODS
  A 43-year-old woman presented with prolonged fever, progressive dyspnoea, diffuse alveolar and interstitial infiltrates. Malignant cells were found on sputum cytology, confirming the diagnosis of lung cancer. She had been treated with corticosteroids and antibiotics but did not receive chemotherapy or radiotherapy. Pneumocystis jiroveci was later found in the sputum but she proved to be HIV negative.
  
  
  CONCLUSIONS
  Unsuspected PCP can occur in chemotherapy and radiotherapy-naïve, HIV-seronegative patients with lung cancer. The complex clinicoradiological manifestations of PCP with underlying lung cancer can lead to delay in diagnosis and may worsen the prognosis.
authors.affiliation: Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510012, China, . skinblack1966@yahoo.com.cn.
authors.forename: Cai
authors.initials: C
authors.lastname: Chuang
authors.forename: Xie
authors.initials: X
authors.lastname: Zhanhong
authors.forename: Gu
authors.initials: G
authors.lastname: Yinyin
authors.forename: Zeng
authors.initials: Z
authors.lastname: Qingsi
authors.forename: Zhong
authors.initials: Z
authors.lastname: Shuqing
authors.forename: Zhong
authors.initials: Z
authors.lastname: Nanshan