Abstract

Distinguishing pilomatricomas (PM) from pilomatrical carcinomas (PMC) can be challenging, especially in partial biopsies.Features favoring PMC include asymmetry,poor circumscription, ulceration,necrosis, cytologic atypia,and infiltrating growth pattern. Pilomatrical tumors (PT) harbor mutations in CTNNB1 that encodes for ?-catenin, a downstream effector in the WNT pathway. Downstream molecules such as CDX2,LEF-1, and SATB2 could thus be used as diagnostic aids. We studied 45 cases (7 PMC, 8 PM, 7 trichoblastoma, 6 BCC, 5 SCC, 10 sebaceous carcinoma and 2 hidradenocarcinoma) by IHC with CDX2,SATB2,?-catenin,LEF-1,Ber-Ep4 and PRAME.The immunoreactivity and intensity was evaluated using semiquantitative estimation of positive lesional cells.The labeling was scored as (0)=negative;(1)=<25% +cells;(2)=26–50% +cells;(3)=51-75% +cells and (4)=>75% +cells.The labeling intensity was scored as negative(0),weak(+1), moderate(+2),and strong(+3). Both PM and PMC showed strong(+3) and diffuse(4) cytoplasmic and nuclear ?-catenin staining; the remaining tumors showed only cytoplasmic expression. All PMC exhibited strong(+3) and diffuse(4) staining for CDX2; 5/7 (71%) PM showed strong(+3) but only focal(1) expression.One PM showed diffuse(3) staining for CDX2 rather than focal. All PMC expressed SATB2 with +3 intensity (80%) and 3-4 labeling (60%); only 2/8 (25%) PM showed +3 intensity with focal(1) positivity. 93.3% and 83.3% of the remaining tumors were negative for CDX2 and SATB2, respectively.PRAME expression was weak(+1) and diffuse(3) in 2/7 PMC but negative in PM.The LEF-1 expression pattern was strong, diffuse nuclear in PT and weak patchy at the center and strong at the periphery in non-PT. 66.6% and 25% of PMC and PM were positive for Ber-Ep4, respectively. Diffuse and strong positivity for CDX2 and SATB2 may distinguish PMC from PM and other potential mimics. Recognition of CDX2 and SATB2 expression in PT can help avoid erroneous diagnosis as a metastasis from GI origin.

Financial Disclosure:
No current or relevant financial relationships exist.