The Diagnostic Utility of Calretinin in Deep Fibromatosis when Dilemma of Spindle Cell Mimic Lesions are Considered: An Immunohistochemical Study

Summary

Nuclear beta catenin is a well known diagnostic marker for fibromatosis but with limited specificity and frequent background stain. Calretinin is an intracellular calcium binding protein that is found to be expressed in many cell types. The study included 20 desmoid cases (abdominal wall fibromatosis) along with 7 cases of intra-abdominal mesenteric fibromatosis and other spindle cell lesions including 11 MPNST (malignant peripheral nerve sheath tumor) cases, 15 cases LMS (leiomyosarcoma), 5 cases synovial sarcoma, 9 cases SFT (solitary fibrous tumor), 19 cases GIST (gastrointestinal stromal tumor), 12 cases Schwannoma and 13 cases neurofibroma which were retracted from the pathology files at Ain Shams University Hospitals with revision of all their available clinical data and available stained sections and then subjected to calretinin immunostain. Calretinin immunohistochemical expression was positive in 85.1% of deep fibromatosis cases including cases of desmoid tumor (18/20) and mesenteric fibromatosis (5/7) (48.1% patchy and 37% diffuse), 33.3% of LMS were presented by diffuse staining, 83.3% of schwannoma were presented by patchy staining. While all cases (100%) of MPNST, synovial sarcoma, SFT and GIST were negative for calretinin. Sensitivity was 85.2% and specificity 80.9% with positive predictive value 59% and negative predictive value 94%. Calretinin can be used to raise the diagnostic accuracy of fibromatosis versus other spindle cell lesions especially when MPNST, synovial sarcoma, SFT, and GIST are considered in the differential diagnosis.