Background Lynch syndrome is the most common form of inherited colorectal cancer (∼3% of cases). Among patients with colorectal cancer tumours, immunohistochemistry (IHC) for mismatch repair proteins has demonstrated validity and utility as a screening test for Lynch syndrome, although guidelines differ on whether screening should be limited to patients at increased risk. IHC can be performed on other Lynch-related tumours, including sebaceous neoplasms, although it is unclear if IHC should be part of routine pathologic evaluation for sebaceous neoplasms.

Objectives To determine the clinical validity and utility of routine IHC testing of sebaceous neoplasms to inform development of guidance on screening for the Muir-Torre variant of Lynch syndrome.

Methods An AHRQ-based analytic framework was created. We conducted comprehensive searches to identify clinical studies that evaluated IHC testing of sebaceous neoplasms as a method of screening for Muir-Torre syndrome. GRADE was used for critical appraisal.

Results The body of evidence included 14 clinically heterogeneous studies representing approximately 300 patients. The weighted mean screen positive rate was 37%. Few studies reported measures of clinical validity, although half of the studies reported the prevalence of visceral malignancy and/or results of germline mutation testing, suggesting possible reporting bias.

Discussion The overall body of evidence is of low quality and does not provide conclusive evidence for or against IHC testing for sebaceous neoplasms, either as a routine protocol or only among patients at high risk for Muir-Torre syndrome.

Implications for Guideline Developers/Users Rapid evidence reviews are useful for informing guidance development on rare/genetic conditions.