Inflammatory pseudotumor of the urinary bladder with aberrant expression of cytokeratin. Report of a case with cytologic, immunocytochemical and cytogenetic findings.

BACKGROUND: Cytologic descriptions of inflammatory pseudotumor of the urinary bladder are exceedingly rare. We describe here an additional case of this disease, including its cytologic features and aberrant expression of cytokeratin. CASE: A 35-year-old male presented with gross hematuria but no history of bladder surgery. Urine cytology revealed a few atypical spindle cells suspicious for sarcoma. Histologically, the lesion consisted of spindle cells of various sizes and shapes, proliferating in irregularly running bundles, but no severe nuclear atypia or pathologic mitosis was found. Immunocytochemically, these cells were unexpectedly positive for cytokeratin as well as for vimentin and muscle actin. All metaphase cells examined revealed a normal male karyotype.
CONCLUSION: Inflammatory pseudotumor must be distinguished in particular from leiomyosarcoma and spindle cell carcinoma. To avoid an erroneous diagnosis, recognition of this entity is important, together with careful histologic examination and awareness of the possible aberrant expression of cytokeratin.