On a cytocentrifuge slide prepared from peritoneal fluid, cells appearing like "fried eggs" with basophilic cytoplasm should be identified as:

The identification of cells that appear like "fried eggs" with basophilic cytoplasm in a cytocentrifuge slide from peritoneal fluid strongly points to mesothelial cells. These cells are normally found on the surface of the peritoneum and can appear in various shapes, including a "fried egg" morphology due to their abundant cytoplasm and distinctive nuclei. The basophilic nature of the cytoplasm is attributed to the presence of ribosomal RNA, which gives these cells their characteristic staining properties.

Mesothelial cells can become prominent in effusions, such as those found in peritoneal fluid, where they may proliferate in response to irritation or inflammation. While macrophages and large lymphocytes can also be present in peritoneal fluid, their appearances differ significantly from that of mesothelial cells. Macrophages tend to have more irregular shapes and may contain phagocytosed particles, while large lymphocytes resemble a different cellular architecture with less basophilic cytoplasm. As a result, the "fried egg" appearance is a definitive characteristic signaling the presence of mesothelial cells.