Medium power: DQ stain
Cluster of large malignant cells stand out in a background of small lymphocytes and histiocytes
Diagnosis: Metastatic lung adenocarcinoma
Medium power: DQ stain
Clusters of large malignant cells stand out in a background of small lymphocytes and histiocytes
Diagnosis: Metastatic lung adenocarcinoma
Medium power: Pap stain
Cluster of large malignant cells stand out in a background of small lymphocytes and histiocytes
Diagnosis: Metastatic lung adenocarcinoma
Medium power: Pap stain
Cluster of large malignant cells with enlarged nuclei, coarse chromatin, prominent nucleoli. Note small lymphocytes for size comparison
Diagnosis: Metastatic lung adenocarcinoma
Medium power: Pap stain
Clusters and single malignant cells that comprise most of the cells in the effusion. May mimic reactive mesothelial cells or histiocytes. Small lymphocytes are present in the background.
Diagnosis: Metastatic lung adenocarcinoma
Cell block: H&E stain
Cluster of large malignant cells with enlarged nuclei, prominent nucleoli, and moderate amounts of vacuolated cytoplasm. Note cell in cell formation suggestive of adenocarcinoma.
Diagnosis: Metastatic lung adenocarcinoma
Cell block: H&E stain
Cluster of large malignant cells with enlarged nuclei, prominent nucleoli, and moderate amounts of vacuolated cytoplasm. Note acinar-like architecture suggestive of adenocarcinoma.
Diagnosis: Metastatic lung adenocarcinoma
Cell block: H&E stain
Clusters and single large malignant cells with focal acinar-like features suggestive of adenocarcinoma. Note intracytoplasmic mucin vacuoles.
Diagnosis: Metastatic lung adenocarcinoma
TTF-1 stain on cell block
Immunostain for TTF-1 highlights the metastatic lung adenocarcinoma cells. Lymphocytes and histiocytes present in the background
Features
• Most common cause of malignant effusions with adenocarcinomas being the most frequent.
• Foreign population of cells that stand out from mesothelial cells and histiocytes
• Exception:
- cells that mimic native cells
- all tumor cells so they all look alike
• Carcinomas typically form cohesive clusters and ball up to form spheres with smooth community borders ; however some tumors shed as single cells (lobular breast carcinoma, gastric signet ring cells). May or may not have malignant features (enlarged irregular nuclei with pleomorphism) but usually have high N:C ratios and coarse chromatin.
• Usually large cells with high N:C ratios
• Often form cell groups, cell balls, papillae
• May have single cells
• Cells usually round up in effusions
• Smooth community borders in adenocarcinoma
• Adenocarcinoma can have cytoplasmic mucin vacuoles
• Nuclei enlarged, irregular, hyperchromatic
• Coarse chromatin
• Prominent nucleoli
• IHC: Tumor cells typically express TTF-1, BerEP4, MOC31, while negative for calretinin (D/D mesothelial cells) and CD68 or CD163 (histiocytes). Napsin A is positive but may also be seen expressed in macrophages.