Calculus Artifact

Abstract

To retrospectively review calculus artifact and compare it with instrument artifact and papillary transitional cell carcinoma (TCC). Voided urine specimens from patients with calculi (65), TCC (low grade, 10, high grade, 34) and history of prior instrumentation (12) were studied. Nineteen specimens of calculus artifact had unremarkable cytology. Forty-six specimens had abnormal single cells or papillary clusters and cell balls or a mixture of both. The papillary groups had smooth as well as irregular borders, a cytoplasmic collar and cells with occasional cytoplasmic vacuoles, slightly increased nuclear/cytoplasmic (N/C) ratio and inconspicuous nucleoli. Squamous preponderance and birefringent crystals were seen. In instrumentation artifact, papillary clusters or three-dimensional cell balls had smooth borders, cytoplasmic collars, an occasional cytoplasmic vacuole, normal N/C ratio, regular nuclear membrane and finely granular nuclear chromatin. In TCC, papillary clusters with loss of polarity and irregular borders were present in both grades but were predominant in low grade TCC. No cytoplasmic collar was noted. In high grade TCC, single cells and nuclear alterations were more pronounced, with increased N/C ratio, hyperchromasia, coarse chromatin, irregular nuclear envelopes, prominent nucleoli and rare mitosis. Calculus artifact can produce papillary clusters masquerading as papillary TCC. Unlike instrument artifact, there may be significant nuclear atypia, which could be reversible. To avoid diagnostic pitfalls, further investigation is suggested after removal of calculus.