Sarcomatoid lesions of the urogenital tract.

Spindle-cell lesions other than sarcomas are relatively rare occurrences along the urogenital tract but include both benign and malignant processes. Inflammatory pseudotumors may occur anywhere along the urothelial tract; they may follow a surgical procedure or appear de novo. Malignant tumors may be classified as sarcomatoid carcinomas or carcinosarcomas according to their degree of differentiation, the latter containing obvious mesenchymal components. Generally both arise in a background of high-grade carcinoma and are of a high pathological stage at the time of initial presentation. For this reason they have a poor prognosis. Because the deferential diagnosis of spindle-cell neoplasms include both benign and malignant lesions, great care must be taken in making the correct diagnosis.