False aneuploidy in benign tumors with a high lymphocyte content: A study of Warthin's tumor and benign thymoma

• Published in: Human pathology Vol. 23; no. 11; pp. 1244 - 1251
• Main Authors: Bañez, Eugenio I., Krishnan, Bhuvaneswari, Qasim Ansari, M., Carraway, Nancy P., McBride, Raymond A.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.11.1992; Elsevier
• Subjects: Adenolymphoma - genetics; Adenolymphoma - immunology; Adenolymphoma - ultrastructure; Aneuploidy; benign tumors; Biological and medical sciences; Cell Nucleus - pathology; DNA ploidy; DNA, Neoplasm - analysis; Flow Cytometry; Humans; image cytometry; Interphase; Lymphocytes; Medical sciences; Pneumology; Salivary Gland Neoplasms - genetics; Salivary Gland Neoplasms - immunology; Salivary Gland Neoplasms - ultrastructure; Thymoma - genetics; Thymoma - immunology; Thymoma - ultrastructure; Thymus Neoplasms - genetics; Thymus Neoplasms - immunology; Thymus Neoplasms - ultrastructure; Tumors of the respiratory system and mediastinum; DNA ploidy; flow cytometry; image cytometry; benign tumors; Chromosomal aberration; Endocrinopathy; Human; Flow cytometry; Parotid gland; Thymoma; Aneuploidy; Differential diagnostic; DNA; Cytogenetics; Adult; Benign neoplasm; Lymphocyte
• ISSN: 0046-8177; 1532-8392
• DOI: 10.1016/0046-8177(92)90292-B

The quality of results of flow cytometric DNA content analysis of formalin-fixed, paraffin-embedded tissue may be affected by a number of preanalytical variables. We performed flow cytometric DNA content analysis on two types of benign tumors to investigate the effect of a prominent lymphocytic component: Warthin's tumor (N = 20) and benign thymoma (N = 8). Malignant tumors (N = 23) were included as DNA aneuploid controls. All tissues studied were archival material processed using Hedley's technique either without prolonged rehydration in water (day 0 samples) or with 24- or 48-hour rehydration (day 1 and day 2 samples, respectively). Image cytometric DNA ploidy analysis was also performed on most cases. Eight cases (40%) of Warthin's tumor and five cases (63%) of benign thymoma showed either hyperdiploid peaks or marked asymmetry on the day 0 DNA histograms; nine of the malignant tumors were aneuploid. The DNA histogram abnormalities of the benign tumors could be gated out by excluding the lymphocyte nuclei. None of the DNA indices of the benign tumors corresponded with expected deviations based on published chromosomal studies. All of the DNA histogram abnormalities of the benign tumors disappeared and/or fused with the main peaks on the day 1 or day 2 samples, except for one case of benign thymoma. All the DNA aneuploid peaks on the malignant tumors persisted with prolonged rehydration. Image cytometric DNA analysis showed a diploid pattern in all benign tumors. We conclude that a high lymphocyte content may be a cause of false aneuploidy in these benign tumors. Furthermore, the degree of rehydration appears to be an important factor in achieving optimum fluorochrome staining of DNA.