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Figure 2.1a — Pigment-Laden Pulmonary Alveolar Macrophages, Bronchoalveolar Lavage [Pap Stain; High Power]. Macrophages within the alveolar spaces may contain variable amounts of pigment, which is not necessarily abnormal. Compare the macrophage at the top right-hand corner, which contains light blue cytoplasm and little pigment, to other macrophages in the field, which contain green pigment material, some of which is coarse and some of which is more granular-appearing. Most pigment is secondary to the breakdown of red blood cells and the heme moiety they contain. The presence of blood may be secondary to a previous hemorrhage. It often can be difficult to definitively characterize pigment material; if necessary, an iron stain can be performed. A patient with a history of metastatic melanoma may pose a diagnostic dilemma.

Figure 2.1b — Pulmonary Alveolar Macrophages, Bronchoalveolar Lavage [Pap Stain; Medium and High Powers]. Pulmonary alveolar macrophages reside primarily in alveolar spaces and their presence alone confirms the adequacy of a bronchoalveolar lavage procedure. The cells have foamy and abundant cytoplasm and oval- to-hyphen-shaped nuclei. The chromatin pattern is bland, with distinct yet small nucleoli. Some cells are binucleate. If macrophages are not seen in an otherwise benign bronchoalveolar lavage, the procedure should be reported as inadequate rather than negative for malignancy.

Figure 2.2a — Benign Respiratory Epithelial Cells, Fine Needle Aspiration [Diff-Quik Stain; High Power]. Benign ciliated respiratory epithelial cells are often present in the background of fine needle aspiration, bronchial brushing and washing, and bronchoalveolar lavage specimens. They have round-to-oval nuclei with regular borders. The cells most often have a columnar shape and are ciliated; the cilia attach to a terminal bar that may be seen as a dense, flat area at the apex of the cell. While cilia may not always be seen in all preparations or in every cell, the presence of cilia and/or a terminal bar is a reassuring finding. Reactive bronchial epithelial cells can have atypical morphologies that mimic adenocarcinoma, as will be demonstrated in later chapters.

33Figure 2.2b — Benign Respiratory Epithelial Cells, Fine Needle Aspiration [Diff-Quik Stain; Medium Power]. The field contains numerous benign respiratory epithelial cells, both singly and in a small fragment. This field contains cells without discernable cilia, but terminal bars can be identified. Note the blandness of the chromatin and similarity of nuclei between the cells.

Figure 2.2c — Goblet Cells, Bronchial Brushing [Pap Stain; High Power]. Goblet cells can be found within the respiratory tract and are intermixed with ciliated bronchial respiratory cells. The mucin contained in goblet cells may appear pink-staining on the Pap stain and have overlap with pink-staining cilia attached to the end of columnar cells. Furthermore, some conditions may result in goblet cell hyperplasia in which goblet cells are more prominent. This may be initially mistaken for adenocarcinoma, but the cells are typically scant, have bland nuclear features, and are intermixed with at least a few ciliated cells.

Figure 2.3a — Benign Mesothelial Cells, Fine Needle Aspiration [Diff-Quik Stain; High Power]. The cells are large, but have round nuclei with regular borders and low nuclear-to-cytoplasmic ratios. Small slits or “windows” between some cells can be seen, indicating a mesothelial origin. The Diff-Quik stain allows for better visualization of the cellular cytoplasm, which may have an amphophilic or “two-toned” appearance. The differential diagnosis would include neoplasms in which cytoplasm is often preserved with round nuclei, such as renal cell carcinoma, melanoma, thyroid carcinoma, and prostate carcinoma.

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Figure 2.3b — Benign Mesothelial Sheet, Fine Needle Aspiration [Pap Stain; Medium Power]. These benign cells form a honeycomb-like pattern in a monolayer sheet; occasionally, this sheet may fold over on itself and appear more complex. By contrast, mesotheliomas tend to have more complex architecture, with three-dimensional structures and rigid projections within fragments. In this case, the cells lack atypical features; in reactive conditions, mesothelial cells can often have markedly typical appearance and have significant overlap with carcinoma or mesothelioma.