Patterns of autophagy in urothelial cell carcinomas--the significance of "stone-like" structures (SLS) in transurethral resection biopsies.

Objectives: To investigate the microtubule-associated protein LC3A, presumed to reflect autophagic activity, in urothelial cell carcinomas (UCC) for its relevance with muscle invasion in transurethral resection (TUR) biopsies. The LC3A antibody is specific for identifying the autophagy-related protein Atg8 and, hence, autophagy-a self-degradation mechanism by which cells recycle their own cytoplasmic constituents, providing with additional energy the rapidly proliferating cells.

Methods: The study comprised 210 TUR specimens of UCC of the urinary bladder: 70 low-grade non-muscle-invasive (NMI, group A), 70 high-grade NMI (group B), and 70 high-grade muscle invasive tumors (group C). These, together with 40 controls, were stained for Atg8/LC3 using an automated immunohistochemical technique.

Results: The LC3A was detected as diffuse cytoplasmic staining, and as dense, spheroidal, "stone-like" structures (SLS) of variable size (1.2-12.0 μm in diameter), typically enclosed within cytoplasmic vacuoles. The LC3A reactivity, whether expressed in the form of SLS or as diffuse cytoplasmic staining, was higher in high-grade UCC than in low-grade disease and, more importantly, it was associated with muscle invasion. The median number of SLS per optical field, per section was 17.0, 19.0, and 37.0 for groups A, B, and C, respectively (A, B vs. C P < 178> 0.0001; A vs. B P = 0.27). The median SLS diameter was 4.9, 5.3, and 9.3 μm for groups A, B, and C respectively (A, B, vs. C P < 0.0001; A vs. B P = 0.03).

Conclusion: It appears that the LC3A protein is closely connected with muscle invasion, but whether this finding is of clinical value in TUR specimens lacking muscularis propria remains to be proven.