colorectal fibroblastic polyp
Tuesday 20 March 2012
Fibroblastic polyps are a recently described distinctive type of colorectal mesenchymal polyp.
The lesions develop in individuals ranging in age from 37 to 84 with a mean of 60 years and with a moderate female predominance.
They occur almost exclusively in the left and distal colon and generally measure < 10 mm in size.
They are solitary lesions that occur alone or coexist with hyperplastic polyps.
They contain a mucosal proliferation of bland, plump, monomorphic spindled cells with oval nuclei arranged as bundles parallel to the surface or as haphazardly arranged sheets with focal periglandular or perivascular arrangements.
Some polyps display a vague zoning arrangement with superﬁcial bundles ofspindle cells arranged parallel to the surface changing to deeper haphazardly arranged sheets of cells.
There may be a thin rim of uninvolved, mildly inﬂamed lamina propria separating the ﬁbroblastic cells from the superﬁcial lining.
The proliferating spindle cells can lead to a wide separation and disorganization ofthe crypts.
The muscularismucosae may appear slightly disorganized.
There may also be a subset of lesions that contain serrated crypts that are referred to as mixed ﬁbroblastic–hyperplastic polyps.
The spindle cell areas in ﬁbroblastic polyps are positive for vimentin and negative for S100 protein, c-kit, epithelial membrane antigen, cytokeratin, CD34, CD68, COX-2, and factor XIIIa.
Ultrastructurally they exhibit the features of ﬁbroblastic cells.