XXXX : A Pathologic and Molecular Study of 8 Cases With Review of the Literature.

@entity1 @entity20027 @entity5 @entity39 @entity31250 @entity44810 @entity146 @entity60597 @entity19957 @entity3 @entity12726 @entity2281 @entity9625 @entity15292
@entity20027 (MTs) are a rare group of @entity5 showing predominant or exclusive myoepithelial differentiation. They are poorly characterized from both a morphologic and genetic standpoint, in particular features that separate benign from malignant behavior. We examined the histologic and immunohistochemical features of 8 primary thoracic MTs and performed fluorescence in situ hybridization for @entity12726 , @entity19957 , @entity44810 , and @entity9625 , as well as several partner genes. Half (4/8) of the MTs occurred in large airways, and 3 had infiltrative borders. All cases showed immunoreactivity for epithelial markers, in conjunction with @entity2281 protein or myogenic markers. MTs showed morphologic characteristics analogous to MTs at other sites, with no @entity5 having ductal differentiation. @entity39 and/or lymphovascular invasion was present in 5 cases, with mitotic activity ranging from 0 to 6 mitoses/2 mm (mean 1). @entity3 occurred in 2 cases, and no @entity1 died of disease. Gene rearrangements were identified in half of the cases, with @entity12726 - @entity31250 , @entity12726 - @entity60597 , and @entity19957 - @entity15292 fusions identified in 1 case each and 1 case having @entity12726 rearrangement with no partner identified. No cases were found to have @entity9625 or @entity44810 abnormalities. Compared with fusion-negative @entity5 , fusion-positive @entity5 tended to occur in @entity1 who were younger (50 vs. 58 y), female (1:3 vs. 3:1 male:female ratio), and demonstrated predominantly spindle and clear cell morphology. Using a combined data set of our case series with 16 cases from the literature, poor prognosis was significantly correlated with @entity3 (P=0.003), @entity39 (P=0.027), and >= 5 mitoses/2 mm/10 high-power field (P=0.005). In summary, we identify a subset of thoracic MTs harboring rearrangements in @entity12726 or @entity19957 , and our data suggest that @entity39 and increased mitotic activity correlate with @entity146 clinical behavior.
