[444] The ER Antibody SP1 May Not Distinguish Breast from Pulmonary Adenocarcinomas in Malignant Pleural Effusions

A Mejias, M Jorda, P Ganjei-Azar, M Garcia, R Grimes-Zeppegno, C Gomez-Fernandez. University of Miami/Jackson Memorial Hospital, Miami, FL

Background: The most common primary sites for adenocarcinomas in malignant pleural effusions include lung and breast. The distinction is clinically important for diagnosis as well as therapeutic management. Morphologic overlap between adenocarcinomas of breast and pulmonary origin often require the use of cell or lineage-specific immunocytochemical markers for this differential diagnosis. TTF-1 is expressed by 75% of primary pulmonary adenocarcinomas and has not been described in carcinomas of breast origin. Estrogen receptor (ER) is expressed by 75% of breast adenocarcinomas but expression in pulmonary adenocarcinomas has been variable and antibody dependent. We investigated the immunocytochemical expression of ER in proven primary lung adenocarcinomas using 1D5, a mouse monoclonal antibody and SP1, a recently described rabbit monoclonal ER antibody.
Design: Forty-two pleural effusions diagnostic for metastatic pulmonary adenocarcinomas (14 women and 28 men) confirmed by clinical presentation and positive immunocytochemistry for TTF-1 were included in this study. Immunocytochemistry for ER using 1D5 and SP1 was performed on alcohol-fixed, previously Papanicolaou-stained slides, using the L-SAB detection system. Any nuclear reactivity for ER was considered a positive result.
Results: A positive nuclear reaction for ER using SP1 was detected in 10 (23.8%) effusion specimens diagnostic for metastatic pulmonary adenocarcinoma. None of the cases were positive for 1D5.
Conclusions: The rabbit monoclonal ER antibody SP1 may yield positive results in pulmonary adenocarcinomas. Caution should therefore be exercised in the use of this antibody alone in distinguishing metastatic breast from pulmonary adenocarcinomas in malignant pleural effusions.
Category: Cytopathology

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 52, Monday Morning

 

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