Calcifying fibrous pseudotumor involving the neck of a five-week-old infant. Presence of factor XIIIa in the lesional cells

Calcifying fibrous pseudotumor is an uncommon lesion characterized by hyali nized collagen, psammomatous or dystrophic calcifications, and a predominan tly lymphoplasmacytic infiltrate. Although the pathogenesis is unclear, a p ossible relationship with other inflammatory "pseudotumors" has been propos ed. We describe the pathology of two right neck calcifying fibrous pseudotu mors present in a five-week-old female infant. The masses had many of the p athologic features of calcifying fibrous pseudotumor. The presence of a flo rid, mixed infiltrate, and the occurrence of more than one lesion in the sa me patient, favor the proposal that calcifying fibrous pseudotumor may be a sclerosing end stage of inflammatory myofibroblastic tumor. However, the p resence of a previously undescribed participation of Factor XIIIa - positiv e cells suggests that the tumor may be of dermal dendrocyte origin.