Micropapillary carcinoma of the urinary bladder: a case report.

BACKGROUND

Micropapillary carcinoma is a rare but unique histologic variant of urothelial carcinoma with an aggressive clinical course. In spite of well-defined clinicopathologic characteristics, the cytomorphologic features in urine specimens have been only rarely described.

CASE: A 78-year-old man presented with gross hematuria, showing a large mass on cystoscopy. Urine cytology contained tight clusters of atypical cells, originally interpreted as high-grade urothelial carcinoma or adenocarcinoma. Final diagnosis was made by histology and immunohistochemical study. On retrospective cytologic review, most presented as small cohesive cellular clusters in the clean background, showing micropapillae without fibrovascular core, morules and occasional rosette-like microacinar structures. A small number of singly scattered cells were also noted. Tumor cells had high-grade nuclear features and occasional cytoplasmic vacuoles. The inside-out pattern was confirmed on cell block by immunohistochemistry for epithelial membrane antigen. Immunoreactivity of E-cadherin disappeared, especially in the cytoplasmic membrane toward the fibrocollagenous stroma.

CONCLUSION

Micropapillary carcinoma had a somewhat characteristic cytologic appearance reflecting part of the histologic features. Cytopathologists should keep in mind the possibility of this rare entity when evaluating small papillary tumor clusters. Careful cytologic examination in combination with cell block morphology and immunohistochemistry may allow early accurate diagnosis and appropriate management.