Discussion:

The nested variant of urothelial carcinoma is a very rare type of cancer, making up just 0.8% of all invasive bladder carcinoma

It is known for the deceptively bland histologic appearance, despite aggressive behavior and poor prognosis (70% mortality between 4 and 40 months)

Nested pattern can be identified by losely packed, haphazardly arranged, and poorly defined urothelial cells infiltrating the lamina propria and the muscularis propria (which is differential from other possible diagnoses)

The nested pattern of the recurrent bladder lesion was not originally identified on prior research, which highlights the difficulty in accurate diagnosis

Difficult to diagnose due to resemblance of foci to benign processes, and infiltrative patterns being hard to assess on small biopsies

Common stains used for positivity include CK7, CK20, p63, Ki-67, CK903 and variable for P53. Some research suggests p53 positivity, and possible subsequent p21 loss, may indicate a higher rate of recurrence and worse survival rate

Accurate and early diagnosis is essential to begin treatment, as diagnosis at advanced stages often have poor prognosis

Treatment is uncertain due to the rarity of the variant, and also but research suggests multimodality therapy including platinum based chemotherapy may be beneficial, as well as cystectomy for early stage tumors