We report on the clinicopathologic features of 115 cases of high-grade urothelial carcinoma of the upper urinary tract with variant histology present in 39 (34%). Variant histology was typically seen in high pathological stage (pT2-pT4) (82%, 32 cases) patients with lower survival rate (70%, 27 cases, median survival 31 months) and consisted in urothelial with one (23%), two (3%), and three or more variants (3%); 4% of cases presented with pure variant histology. Squamous divergent differentiation was the most common variant (7%) followed by sarcomatoid (6%) and glandular (4%), followed by 3% each of micropapillary, diffuse-plasmacytoid, inverted growth, clear cell glycogenic, or lipid-rich. The pseudo-angiosarcomatous variant is seen in 2%, and 1% each of nested, giant-cell, lymphoepithelioma-like, small-cell, trophoblastic, rhabdoid, microcystic, lymphoid-rich stroma, or myxoid stroma/chordoid completed the study series. Loss of mismatch repair protein expression was identified in one case of upper urinary tract carcinoma with inverted growth variant (3.6%). Variant histology was associated to pathological stage (p = 0.007) and survival status (p = 0.039). The univariate survival analysis identified variant histology as a feature of lower recurrence-free survival (p = 0.046). Our findings suggest that variant histology is a feature of aggressiveness in urothelial carcinoma of the upper urinary tract worth it to be reported.
