Calculus artifact - A challenge in urinary cytology

OBJECTIVE: To retrospectively review calculus artifact and compare it with instrument artifact and papillary transitional cell carcinoma (TCC). STUDY DESIGN: Voided urine specimens from patients with calculi (65), TCC ( low grade, 10, high grade, 34) and history of prior instrumentation (12) we re studied. RESULTS: Nineteen specimens of calculus artifact had unremarkable cytology. Forty-six specimens had abnormal single cells or papillary clusters and ce ll balls or a mixture of both. The papillary groups had smooth as well as i rregular borders, a cytoplasmic collar and cells with occasional cytoplasmi c vacuoles, slightly increased nuclear/cytoplasmic (N/C) ratio and inconspi cuous 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 va cuole, normal NIC ratio, regular nuclear membrane and finely granular nucle ar chromatin. In TCC, papillary clusters with loss of polarity and irregula r 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 nucl ear alterations were more pronounced, with increased NIC ratio, hyperchroma sia, coarse chromatin, irregular nuclear envelopes, prominent nucleoli and rare mitosis. CONCLUSION: Calculus artifact cart produce papillary clusters masquerading as papillary TCC. Unlike instrument artifact, there may be significant nucl ear atypia, which could be reversible. To avoid diagnostic pitfalls, furthe r investigation is suggested after removal of calculus.