The histopathologic spectrum of regression in atypical fibroxanthoma.
BACKGROUND
Atypical fibroxanthoma (AFX) with prominent fibrosis, sclerosis and hyalinization, and near-total tumor regression is rare.


METHODS
Eight cases of AFX presenting with fibrosis were reviewed as to their tumor architecture, the degree and pattern of fibrosis and the associated inflammatory cell infiltrate.


RESULTS
Seven of eight cases had an exophytic architecture, with ulceration in one case. The degree of fibrosis ranged from 10% to 90%. Early fibrosis (2/8 cases) occurred as thickened sclerotic collagen bundles, either dispersed between the neoplastic cells or as septa imparting a multilobular appearance. Advanced fibrosis (6/8 cases) was associated with lamellar sclerosis, keloidal features, hyalinization and with near-total tumor replacement. Prominent fibrosis rimming the periphery was present in all tumors. An associated lymphoid cell infiltrate with plasma cells and occasionally eosinophils was observed.


CONCLUSIONS
Fibrosis with prominent sclerosis and hyalinization replacing the tumor is rare in AFX. Advanced fibrosis, in the absence of a history of prior trauma or surgery, may indicate spontaneous regression. These cases emphasize the importance of recognizing this subset of AFX in order to avoid misinterpretation, particularly in cases with few residual atypical cells.
Stefanato
Catherine M
CM
Department of Dermatopathology, St John's Institute of Dermatology, St Thomas' Hospital, London, UK. catherinestefanato@gmail.com
Robson
Alistair
A
Calonje
J Eduardo
JE
D000368:Aged; D000369:Aged, 80 and over; D002610:Cheek / Q000473:pathology; D005260:Female; D005355:Fibrosis / Q000473:pathology; D006258:Head and Neck Neoplasms / Q000473:pathology*; D018219:Histiocytoma, Benign Fibrous / Q000473:pathology*; D006801:Humans; D007627:Keloid / Q000473:pathology; D008297:Male; D012535:Scalp / Q000473:pathology; D012878:Skin Neoplasms / Q000473:pathology*; D014973:Xanthomatosis / Q000473:pathology*