[1600] Diagnostic Accuracy of Malignant Pleural Effusion Cytology in 2008

F Galateau-Salle, N Le Stang, V Abonnet. CHU Caen, Caen, France

Background: The reported diagnostic accuracy of pleural effusion cytology has varied from 60 to 95% for the diagnosis of metastatic carcinoma [MC] to unsatisfactory (30%) for mesothelioma [MM]. The aim of the study was to evaluate, in 2008 the diagnostic accuracy of conventional pleural effusion cytology [PEC] in our institution, and to assess the usefulness of p16/CDKN2A deletion by FISH as a diagnostic marker for the distinction between benign and malignant mesothelial cells.
Design: A series of 3483 exfoliative PEC and 1659 biopsies were collected from the department of Pathology of CHU Caen during the period 1998-2008. They were systematically analyzed and compared with clinical and or histological follow up. Additionnally a series of 143 patients with a diagnosis of MM and of 347 patients with a diagnosis of MC made either by cytology and /or by a biopsy were selected according to the French system of codification ADICAP code. A dual color FISH for p16/CDKN2A and chromosome 9 centromere was performed either on frozen or paraffin embedded cell blocks from 20 reactive mesothelial hyperplasia [RMH] and 17 positive effusions for MM.
Results: From the 3483 PEC, a diagnosis of malignancy was performed in 12% (n=411), and of benign disease in 88% (n=3072). Among the 411 patients with a positive cytology for malignancy a diagnosis of MM was observed in 9% of cases, of MC in 84% and of lymphoma in 7%. From the series of 143 patients with a positive PEC for MM, the diagnosis was made by thoracoscopy/surgical biopsy in 50% (n=71), by cytology alone in 3% (n=5) and by both in 47% (n=67). From the series of 347 patients with a diagnosis of MC, the diagnosis was made respectively by thoracoscopy/surgical biopsy in 38% (n=133), by cytology alone in 17%(n=58), by both in 45% (n=155). The sensitivity of cytological diagnosis was respectively 36% with a predictive positive value [PPV] of 88% for MM and 52% with a PPV of 90 % for MC. When we compare the period of time from 1998 -2003 to the period from June 2003-2008, the sensitivity and PPV were respectively 19% with a PPV of 83% and 47% with a PPV of 90% for the diagnosis of MM (p<0.05) and of 45% with a PPV of 91% and 57% with a PPV of 90% for MC (p=0.17). Homozygous CDKN2A deletion was detected by FISH in 7 /17 MM cases and in none of RMH (0/20).
Conclusions: Our results show that the diagnostic accuracy of PEC is improving due to a better definition of criteria, and to the use of immunohistochemistry. The detection of homozygous deletion CDKN2A by FISH could be extremely useful for the diagnosis of MM over RMH.
Category: Pulmonary

Tuesday, March 10, 2009 11:00 AM

Platform Session: Section F 2, Tuesday Morning