title: Retrospective analysis of unknown primary cancers with malignant pleural effusion at initial diagnosis.
abstract: Malignant pleural effusion (MPE) can occur during the progression of various cancers. However, factors, such as the incidence of MPE associated with different types of cancers and its potential for diagnosing previously undetected cancers, are unknown. Moreover, MPE may accompany potentially curable cancers or those with a favorable survival prognosis with adequate treatment. The present study determined the types of cancers accompanied by MPE at initial diagnosis and investigated appropriate related methods for diagnosing previously unknown cancers.
  
  
  
  We retrospectively reviewed the medical records of 35 patients with MPE at initial cancer diagnosis between 2004 and 2012. We evaluated the patient characteristics, final diagnosis, and diagnostic processes.
  
  
  
  Of the 35 patients, 10 had lung cancer, seven ovarian or peritoneal cancer, four malignant pleural mesothelioma, one breast cancer, one lymphoma, one pancreatic cancer, and 11 had cancers of unknown origin. Diagnoses of the primary lesions were confirmed using the MPE cellblock method for seven of 11 patients (63.6%), by excisional biopsy or aspiration from other sites in four of nine patients, by exploratory laparotomy in two of three patients, and by peritoneal washing cytology in five patients.
  
  
  
  Lung cancer and cancer of unknown origin are major causes of MPE at initial presentation. However, these groups also contain cancers that are curable and those with good long-term prognosis. The MPE cellblock method represents an accurate method for identifying cancer origin.
authors.affiliation: Department of Thoracic Oncology and Respiratory Medicine Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan; Department of Medical Oncology, Graduate School of Medicine Chiba University Chiba Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ebata
authors.affiliation: Department of Thoracic Oncology and Respiratory Medicine Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Okuma
authors.affiliation: Department of Thoracic Oncology and Respiratory Medicine Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Nakahara
authors.affiliation: Department of Thoracic Oncology and Respiratory Medicine Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Yomota
authors.affiliation: Department of Thoracic Oncology and Respiratory Medicine Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Takagi
authors.affiliation: Department of Thoracic Oncology and Respiratory Medicine Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Hosomi
authors.affiliation: Department of Pathology Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Eichi
authors.initials: E
authors.lastname: Asami
authors.affiliation: Department of Chemotherapy Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Omuro
authors.affiliation: Department of Pathology Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Tsunekazu
authors.initials: T
authors.lastname: Hishima
authors.affiliation: Department of Thoracic Oncology and Respiratory Medicine Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Bunkyo Japan.
authors.forename: Tatsuru
authors.initials: T
authors.lastname: Okamura
authors.affiliation: Department of Medical Oncology, Graduate School of Medicine Chiba University Chiba Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takiguchi
keywords: Lymphoma; malignant mesothelioma; malignant pleural effusion; ovarian cancer
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