Indian file pattern of adenocarcinoma cells in effusions.

Objective: To determine the prevalence of the Indian file pattern of adenocarcinoma cells in malignant serous effusions.

Study Design: Twenty-five malignant and 10 benign effusion samples were selected. Clinical data, including the sites of the primary neoplasms, were noted. The presence or absence of Indian file arrangement of carcinoma cells and other patterns were recorded.

Results: Seven of the 25 positive cases showed Indian file arrangement, whereas none of the negative cases did. Their number did not show any correlation with the type and site of the primary neoplasms. In most of the 7 cases other patterns, such as 3-dimensional balls and papillations, were also present.

Conclusion: Cells in Indian file in serous effusions are strongly suggestive of metastatic carcinoma. They are not specific to any particular site of the primary adenocarcinoma.