Fine needle aspiration biopsy of idiopathic retroperitoneal fibrosis.

Objective: To report three cases of idiopathic retroperitoneal fibrosis (IRF) diagnosed by fine needle aspiration (FNA) biopsy and confirmed by histologic examination. To our knowledge, this is the first report on the FNA findings in IRF.
Study Design: Specimens were obtained under computed tomographic guidance using the standard technique. Half the smears were ethanol fixed and stained with Papanicolaou stain, and the other half were air dried and stained with Diff-Quik. A cell block was prepared in all cases.
Results: Similar findings were seen in all three cases. The predominant elements were fibrous tissue and inflammatory cells, which occasionally occurred together but often were separate. The inflammatory cells were predominantly small lymphocytes, with occasional plasma cells, histiocytes and neutrophils. Smears from one case showed the inflammatory component only, but the cell block in all three cases showed both elements. The diagnosis of IRF was suggested in two of the three cases. All patients underwent laparotomy for diagnostic confirmation, and two had therapeutic resection of the lesion. Histologic material reflected the FNA findings, showing hyalinized fibrous tissue and an inflammatory cell infiltrate consisting of lymphocytes, plasma cells, histiocytes and neutrophils. No infection, arteritis or malignancy was present.
Conclusion: Although the FNA picture is nonspecific, in combination with clinical and radiologic findings it is highly suggestive of a diagnosis of IRF. A presumptive diagnosis allows a rational approach to further evaluation and therapy, which, in most cases, is an exploratory laparotomy with ureterolysis.