Clinical Pathology: Urinalysis, Body Fluids, Clinical Microscopy

546) An 89-year-old man with shortness of breath and symptoms of pneumonia had a chest x-ray that demonstrated a small pleural effusion. The types of cells seen in the aspiration are shown in the figure. Which one of the following is the best diagnosis?

• Microscopic description: Cells with foamy vacuolated cytoplasm and ovoid to kidney-shaped nuclei. There is also a single cell of a different type with dense cytoplasm (mid left).

• Pleural effusions and ascites fluid typically have a combination of mesothelial cells and histiocytes.

• Both mesothelial cells and histiocytes are normal constituents of the pleural and peritioneal cavities.

• Benign mesothelial cells and histiocytes are present as single cells. In pelvic washing specimens, mesothelial cells shed as two-dimensional sheets.

• Identification of clusters of epithelioid cells and two-celled populations suggest malignancy. Immunostains may be necessary to confirm the morphologic impression and determine the identity of the primary tumor.

• Lymphocytes, whether benign or neoplastic, occur as single cells. Lymphocytes are smaller than mesothelial cells and histiocytes.

Cibas ES, Ducatman BS: Cytology. Diagnostic Principles and Clinical Correlates. 3rd ed. Philadelphia: Saunders Elsevier, 2009.

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