Related Experiment Video
Updated: Feb 15, 2026

Local Anesthetic Thoracoscopy for Undiagnosed Pleural Effusion
Published on: November 10, 2023
Reactive histiocytic proliferation in the pleural fluid mimicking metastatic signet ring adenocarcinoma
Fatima Mir1, Anam Naumaan1, Hussein Alnajar1
1Department of Pathology, Rush University Medical Center, Chicago, Illinois.
Abstract:
Reactive nodular and diffuse histiocytic proliferations of mesothelial and non-mesothelial lined sites have been sporadically reported in the literature. However, there is no cytologic literature describing this process. We report a case of reactive histiocytic proliferation mimicking a metastatic signet ring adenocarcinoma in pleural fluid from a 33-year-old white male. Ancillary studies such as immunohistochemistry should be used to elucidate the cell of origin and avoid diagnostic errors.
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Cross-reactivity
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