Collagen deposition is observed in several cutaneous neoplasms and its derivation is variable. It can represent (1) a mesenchymal component of a biphasic tumor, (2) a desmoplastic host response to a neoplasm, or (3) a product of the tumor cells. The result is that collagenous (desmoplastic) variants of many cutaneous neoplasms are well recognized. In regard to atypical fibroxanthoma (AFX), conventional wisdom holds that intratumoral collagen is not commonly observed, apart from the rare sclerotic subtype of the neoplasm. This has not been our experience. The relatively frequent observation of keloidal collagen in AFXs and the dearth of information in the literature about this phenomenon prompted us to investigate the matter. All cases of AFX diagnosed at our institution within a 10-year period (1999-2008) were reviewed. The group included 64 males and 27 females with a mean age of 75 years. The majority of the cases (92%) were located on the head or neck. The conventional pleomorphic subtype of the tumor was encountered most frequently (67%). In 17 of the 91 cases (19%), prominent intratumoral keloidal collagen was present. This morphological observation poses interesting questions: (1) Is the collagen part of a host response to the neoplasm or is it a product of the tumor cells? (2) If the latter, does it cast light on the controversial histogenesis of AFX? (3) Does it signify an involutional stage of the tumor and imply a favorable prognosis? (4) Is it related to the “sclerotic” variant of the tumor? We discuss the above quandaries and emphasize the need to register this variant of AFX amongst other morphological subtypes of the tumor. The goal is to facilitate accuracy in diagnosis and to promote further investigation.
From the Division of Anatomical Pathology, Department of Pathology, Capital District Health Authority and Dalhousie University, Halifax, Nova Scotia, Canada.
Reprints: Dr. Noreen Walsh, MD, MRCPI, FRCP(C), FRCPath (UK), Head, Division of Anatomical Pathology, Room 742, D.J. Mackenzie Building, Capital District Health Authority (VG Site), 5788 University Avenue, Halifax, Nova Scotia B3H 1V8, Canada (e-mail: email@example.com).