Isolated pleural effusion with hematopoietic cells of mixed lineage in a patient receiving granulocyte-colony-stimulating factor after high-dose chemotherapy.

A 43-yr-old woman with recently diagnosed breast carcinoma presented with a right pleural effusion after a cycle of adjuvant, high-dose chemotherapy supported by peripheral blood progenitor cells (PBPC) and granulocyte-colony-stimulating factor (G-CSF, Filgrastim). Cytologic examination of the pleural aspirate yielded highly cellular material composed predominantly of cells of myeloid and macrophage/monocytic lineages. Despite clinical concern of a malignant effusion, the combination of cytologic and immunophenotypic examination yielded the correct diagnosis of a nonneoplastic effusion related to underlying pleural inflammation and possibly the administration of G-CSF.