Evidence for the formation of metaplastic bone from pericytes in calcifying fibroblastic granuloma


Professor P. Sloan
University Dental Hospital of Manchester,
Higher Cambridge Street,
Manchester M15 6FH, UK
Tel.: +44 161275 6788
Fax: +44 161275 6797
e-mail: P.Sloan@man.ac.uk


Background:  The calcifying fibroblastic granuloma (CFG) is a variant of epulis characterised histologically by calcified nodules and metaplastic bone formation and clinically by its pattern of frequent recurrence. Recent evidence suggests that calcified nodules and bone may form directly from non-haemopoetic pericytes in a variety of situations. This study aimed to test the hypothesis that metaplastic bone formation in CFG may be the result of a pericytic differentiation pathway.

Methods:  A series of 16 cases of CFG meeting the criteria of Lee were reviewed and stained using markers which aid the identification of pericyte (smooth muscle actin, von Willebrand's factor, monoclonal antibody 3G5) and osteoblast (AML-3) lineages.

Results:  The cells in mineralising areas of CFG resembled pericytes morphologically. Often, calcified nodules were observed within the vascular basement membrane and nodules frequently formed the nidus for reactive bone formation. The pericyte-like cells were positive for smooth muscle actin and AML-3 and were negative for von Willebrand's factor.

Conclusions:  These data provide circumstantial evidence for a pericytic lineage in CFG.