Anatomical Pathology Interesting Case Conference

Discussion:

Von Brunn’s nests:

• Regularly spaced large nests, that do not
• The Central lumen is often formed, sometimes
• Immunostaining has little affinity to MIB-1
• Can present with focal atypia

Nested Variant Urothelial Carcinoma

• Infiltrative pattern of irregular confluent variably sized nests into the lamina propria and muscularis propria. The urothelium is often spared.
• The lumens and spaces are often empty however may present with necrotic debris or have PAS stainable material, the carcinoma cells forming and lining the spaces do not have secretory/glandular cytoplasmic differentiation.
• Cytologically bland features include focal atypia, which if present in the muscularis propria excludes the possibility of a benign lesion.
• Often involves the ureteric orifices

Cytogenetics and IHC

Molecular / cytogenetics:

• Loss of p27. Has also been associated with increased progression and proliferation of the disease
• (FOXA1+ / CK5/6-)
• TERT promotor mutations
 

Positive Stains:

 

• CK7, CK20, CK903, p63, Ki-67

Negative Stains:

• P53, bcl-2  generally negative
• Loss of p27  present in the deep component

Microscopic (histologic) description:

• The Tumor is characterized by closely irregularly packed bland confluent nests of poorly defined urothelial cells infiltrating the lamina propria and the muscularis propria.
• Generally, there is no evidence of surface epithelial involvement(urothelium)
• Presence of focal atypia (mild pleomorphism, slightly increased nuclear/cytoplasmic ratios, occasional prominent nucleoli, and rare mitotic figures)Atypia may become more prominent with a greater depth of invasion.
• Deceptive benign appearance, should be ruled out as it can be mistaken for a benign bladder lesion called Von Brunn’s nests.