Usefulness of histologic homogeneity estimation of muscle-invasive urinary bladder cancer in an individual prognosis: A mapping study

Objectives. To examine the histologic homogeneity of muscle-invasive urothelial cell carcinoma of the bladder, with conventional and nonconventional (eg, squamous, glandular, or variants) differentiation, to assess its influence on prognosis. Methods. With organ mapping, we investigated 38 cystectomy specimens. Each entire bladder was cut into 88 slices according to an identical topographic scheme. From all the bladder slices, 1231 slices that included tumor were chosen for the histologic study. We examined the diagnostic significance, extension, and number of histologic differentiation types. Results. The extension of nonconventional differentiation, with any proportion of histologic type, had an unfavorable impact on survival time. The number of nonconventional differentiation types increases in the presence of a sarcomatoid, an undifferentiated, a nested, or a micropapillary pattern. The increased number of differentiation types had an unfavorable influence on survival time. Patients with a more than 80% classic urothelial cell carcinoma pattern had a favorable prognosis, which increased further with increasing percentages of this differentiation type. Conclusions. Muscle-invasive urinary bladder cancers are not a homogenous group of tumors. Our results suggest that a precise assessment of the extension and number of histological differentiation types may be an individual prognostic factor. Conventional differentiation with at least 80% extension seems to be prognostically favorable. Nonconventional differentiation, especially with greater extension and a greater number of types, could imply a worse prognosis.