Long microvilli of mesothelioma are conspicuous in pleural effusions processed by Ultrafast Papanicolaou stain

Mesothelioma

Mesothelioma arises from the surface serosal cells lining the pleural, peritoneal, and pericardial cavities. It has three variants including: epithelioid, sarcomatous/desmoplastic, and biphasic types. Mesothelioma cells, predominantly of the epithelioid type, can shed into effusions as sheets, clusters/ morulae, papillae, or single cells. The challenges to cytologic diagnosis of mesothelioma are two-fold: 1. distinguishing mesothelial cells from metastatic malignant (most commonly carcinoma) cells; 2. distinguishing reactive mesothelial from mesothelioma cells. Immunocytochemistry is a helpful aid to cytologic evaluation for the former. The distinction of reactive mesothelial cells from mesothelioma can be more difficult, as there is considerable overlap in their appearances in effusion specimens. Recently developed ancillary molecular and genetic tests are proving to be useful in confirming the diagnosis of malignant mesothelioma in cytology specimens.

Significance of flower pot cells in effusion cytology

Cells with long polar hair-like processes referred to as 'flower pot cells' are a rare but beautiful morphological feature observed in effusions of diverse etiologies. This report describes these cells in effusions seen in ovarian borderline serous tumours, malignant mesothelioma and in reactive mesothelial cells with or without accompanying malignant cells. These processes were better appreciated in air-dried May-Grunwald-Giemsa stained smears.

Rapid-air-dry papanicolaou stain in canine and feline tumor cytology: a quantitative comparison with the Giemsa stain

The Papanicolaou stain is a gold-standard staining method for tumor diagnosis in human cytology. However, it has not been used routinely in veterinary cytology, because of its complicated multistep procedure and requirement for wet fixation. Currently, a rapid Papanicolaou stain using air-dried smears is utilized in human cytology, but usefulness of this rapid-air-dry Papanicolaou (RAD-Pap) stain in the veterinary field has not been fully evaluated. The purpose of this study was to evaluate the usefulness of the RAD-Pap stain by using quantitative analysis. Air-dried impression smears were collected from tumor specimens and stained with RAD-Pap and Giemsa. Twelve parameters representing the criteria of malignancy were quantitated, and characteristics of the RAD-Pap were evaluated statistically. The RAD-Pap stain could be applied to all the smears, and images of nucleoli and chromatin patterns were clear and detailed. In quantitative analysis with the RAD-Pap stain, but not with the Giemsa stain, dispersion of nucleolus size and dispersion of nucleolus/nucleus ratio in malignant tumors were significantly higher than those in benign tumors. These findings demonstrated that the RAD-Pap stain was useful for obtaining detailed nuclear information, and the ability to differentiate benignity and malignancy by nucleolus findings was a principal advantage of this stain. This RAD-Pap stain could be routinely used as a supportive staining method in veterinary diagnostic cytology.

Fine-needle aspiration of malignant mesothelioma with unusual morphologic features: A case report

Malignant mesothelioma is an aggressive neoplasm linked to asbestos exposure. Most mesothelioma patients present with pleural effusion and the fluid is typically sent for cytological examination. Therefore, cytopathologists are most familiar with features of mesothelioma in fluid preparations. We present here a case of malignant mesothelioma with unusual cytological features diagnosed on FNA. The diagnosis was confirmed by immuno-histochemical and electron microscopic studies. In addition, we compare the cytomorphological features observed in malignant effusion versus fine-needle aspiration.