Clear cell renal carcinoma strays from its textbook immunoprofile

Design

Single-institution descriptive cohort of molecularly verified tumours

Population

108 clear cell renal cell carcinomas (54 primary, 54 metastatic) with concurrent immunohistochemistry

Primary outcome

Immunostaining patterns correlated with architecture and driver mutations

Effect

Cytokeratin 7 positive in 30% (diffuse 16%); CA9 negative in 15% of metastases

The classic immunoprofile of clear cell renal cell carcinoma — CA9 positive, cytokeratin 7 negative — is built from morphologically selected tumours, and aberrant staining is a recognised trap. This study profiled 108 molecularly verified cases, identified by VHL alteration or 3p loss, correlating stains with architecture and driver mutations.

Cytokeratin 7 was positive in 30% overall, with diffuse strong staining in 16% — more common in primary than metastatic tumours (45% vs 13%), in lower-grade architecture, and in PBRM1 wild-type tumours. CA9, usually diffuse, was negative in 15% of metastatic tumours. Genotype tracked with phenotype: PBRM1-mutated tumours tended to be cytokeratin 7 negative, CA9 positive and PAX8 negative, while BAP1-mutated tumours showed higher-grade architecture and loss of CD10.

The practical message is to expect deviation from the textbook panel, especially in metastatic or higher-grade tumours. A cytokeratin 7-positive or CA9-negative renal tumour does not exclude clear cell carcinoma, and a molecular check resolves the genuinely ambiguous case.

• 108 molecularly verified clear cell renal cell carcinomas, correlated with architecture and mutations.
• Cytokeratin 7 was positive in 30% (diffuse strong in 16%), more often in primary and lower-grade tumours.
• CA9 was negative in 15% of metastatic tumours, against its usual diffuse positivity.
• PBRM1-mutated tumours tended to be cytokeratin 7 negative, CA9 positive, PAX8 negative.
• A cytokeratin 7-positive or CA9-negative renal tumour does not exclude clear cell carcinoma.

Why it matters

It quantifies how often the standard renal immunopanel misleads, which matters most on a small biopsy of a metastasis.

Don't overread it

This is a single-institution descriptive cohort; the genotype-phenotype associations are correlations, not diagnostic rules.

The statistics, in plain English

These proportions describe how often real tumours deviate from the expected panel; the associations with mutation status are significant but descriptive, showing correlation rather than a rule you can apply to a single case.

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