In 1995, a two-year-old girl with no history of any medical problems
presented with a mass on the volar radial aspect of the right thumb
at the level of the metacarpophalangeal joint and extending onto the
thenar eminence. The family had just recently noticed the mass.
We observed normal motion of all of the thumb joints, with normal
active function of the extensor pollicis longus and the flexor pollicis longus.
There was no triggering, and the patient appeared to use the hand
normally. The mass was mobile and did not seem to be painful. Sensory
testing could not be done because of the child’s age. Radiographs
did not demonstrate any osseous involvement, but there was calcification
in the soft-tissue mass.
At surgery, a flesh-colored lobulated mass measuring 1.7 by 1.0
by 0.9 cm was found (Fig. 1). The radial digital nerve of the
thumb was closely adherent to the mass on its inferior surface.
The mass was dissected out with use of 3.5-times loupe magnification,
and the radial digital nerve was not compromised.
Microscopic sections revealed a spindle-cell neoplasm with one
mitosis per ten high-powered fields. There was no atypia. Histological
sections stained with hematoxylin and eosin revealed a pattern of interlacing
bundles of spindle cells (Fig. 2), with scattered foci of chondroid
differentiation (Fig. 3). Sections with special staining,
including S-100 protein, smooth-muscle actin, and Masson trichrome,
were reviewed. Diffuse background staining with S-100 protein was
noted, but this was thought to be nonspecific; there was definite
staining with smooth-muscle actin; and smooth-muscle elements were
noted on Masson trichrome staining. A pathological diagnosis of
calcifying aponeurotic fibroma was made.
Postoperatively, the patient did well, and the lesion had not
recurred at the time of this writing.