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Background: Microcystic urothelial carcinoma (MUC) is a rare variant of urothelial carcinoma with histological appearances similar to begin lesions. Thus far, approximately 50 cases have been reported. Here, we investigated the clinicopathological features of MUC. Methods: Clinical data and paraffin-embedded tissue blocks were collected. Immunohistochemical staining and polymerase chain reaction–Sanger sequencing were performed to detect the phenotype and TERT mutation status of MUC, respectively. Results: The mean patient age was 58.8 ± 14.5 years, with a male predominance (8:2). The pathological stage was T1 in one case, T2 in three cases, T3 in four cases, and T4 in two cases. Tumor metastases or death occurred in all five patients who were followed up within 1–3 years. Histological analyses revealed microcystic, tubular, cribriform, and occasionally cord-like structures, which generally lacked interstitial reactions. The lumens were empty, contained eosinophilic secretion, or were filled with mucin. The microcysts/tubules/cribriform patterns were lined by flat, cuboid, signet ring, or columnar types of epithelia. The cuboid, signet ring, and columnar types represented "glandular metaplasia" or glandular differentiation of urothelial carcinoma. Immunohistochemistry analyses revealed distinct co-expression patterns involving the luminal markers FOXA1 and GATA3, as well as the basal markers CK5/6 and CD44. All 10 cases exhibited a luminal phenotype according to the GATA3+/CK14- criterion, whereas nine cases exhibited a luminal phenotype according to the FOXA1+/CK14- criterion. The telomerase reverse transcriptase-C228T mutation was detected in seven cases. Conclusions: MUC is a rare variant with a deceptively benign form of urothelial carcinoma, which is generally identified as a late-stage tumor with a poor prognosis. It exhibits distinct co-expression of luminal and basal markers, along with the TERT-C228T mutation. [ABSTRACT FROM AUTHOR]

Background: Phyllodes tumors belong to a spectrum of biphasic fibroepithelial lesions and are most commonly found in the breast. They are extremely rare in the urinary tract and only one case of bladder phyllodes tumor has been reported. Case presentation: We present a 69-year-old man with gross hematuria without an apparent cause. Computed tomography-urography and cystoscopic examination revealed a 5 × 4 cm lesion in the right ureteral orifice. He underwent a laparoscopic nephroureterectomy and partial cystectomy. Postoperative pathology confirmed a leaf-like structure consisting of myxoid stroma and peripheral urothelium. Stromal cells were spindle-shaped and stellate in appearance with no conspicuous cytological atypia or mitosis. The outlining urothelium had varying degrees of dysplasia, while in areas with moderate-to-severe dysplasia, active mitotic activity, abnormal giant cells, and focal early infiltration were observed. Overall, this case had the morphological features of benign phyllodes tumors and concomitant invasive urothelial carcinoma inside. The patient remained disease-free at 7 months after surgery. Conclusion: We report the first ureteral tumor with the morphological characteristics of a phyllodes tumor and concomitant invasive urothelial carcinoma inside. Considering the potential for local recurrence of phyllodes tumors and invasive urothelial carcinoma, long-term clinical and radiological follow-up of such lesions are advisable. [ABSTRACT FROM AUTHOR]