Upper urinary tract urothelial carcinomas (UTUCs) are rare malignant neoplasms, representing about 5% of all urothelial carcinomas (UCs). The incidence of primary UTUC in the renal pelvis and calyx is quite rare. UTUC is a high-grade tumour with a poor prognosis at presentation. Characteristically, UTUC presents with symptoms such as gross and microscopic hematuria or flank pain. Its mode of definitive diagnosis remains histopathology examination, despite using computed tomography urography (CTU) as the gold imaging standard. However, atypical clinical presentations and abnormal radiologic findings could lead to misdiagnosis of UTUC.

We report a 59-year-old male who presented with recurrent left flank pain of 2 years duration, and an episode of hematuria. A CTU showed no classic radiologic feature of upper UCs; however, his abdominal magnetic resonance imaging was suggestive. He subsequently had a left radical nephroureterectomy. The post-operative histology report showed a primary invasive high-grade UC of the left renal pelvis and calyx. He was counseled on the findings and placed on surveillance. There are few reported cases of UTUC of the renal pelvis and renal calyx; given that it is a rare malignancy. This is quite concerning, especially with the missed imaging finding by CTU.