An 11-year-old Japanese girl noticed a small nodule, with mild tenderness, on the right index finger 5 years before visiting our outpatient clinic. She had no familial history of
neurofibromatosis or past history of traumatic injury at the site of the
tumor. Physical examination revealed a slightly elevated, subcutaneous, nodular
tumor in the volar aspect between the proximal and distal interphalangeal joints of the digit (Fig. 1A). By magnetic resonance imaging examination, the
tumor showed low density on both T1- and T2-weighted images, and was located just adjacent to the tendon with no invasive signs. The
tumor was extirpated; at operation, it was well circumscribed and mobile without adhesion to adjacent tendon or nerve, and was easily removed. Grossly, the
tumor was a well-circumscribed, firm nodule (10 mm x 8 mm x 5 mm in size) (Fig. 1B). The cut surface was whitish, homogeneous, and solid without cystic lesions. Histologically, it was an unencapsulated, paucicellular dense, fibrous nodule with a concentric circular arrangement of
collagen bundles (Fig. 2A). Amongst the fibrous bundles, a small number of ovoid/epithelioid or plump spindle cells were arranged in a corded, trabecular, or whorled (onion bulb-like) pattern (Fig. 2B); a storiform pattern was not noted. These cells were relatively uniform and had a somewhat elongated, slightly hyperchromatic nucleus with fine granular
chromatin. Neither nuclear pleomorphism nor multinucleated cells were evident, and
necrosis and mitotic figures were not observed.
Periodic acid-Schiff (PAS)
stain after
diastase digestion highlighted the corded or whorled pattern of the
tumor cells by encasing them. For immunohistochemical examination,
formalin-fixed,
paraffin-embedded serial tissue sections were stained by a labeled
streptavidin-
biotin method. The
tumor cells were positive for
vimentin and
epithelial membrane antigen (EMA) (Fig. 3A), and negative for pan-
cytokeratin,
carcinoembryonic antigen (CEA), CD34, alpha-smooth muscle actin,
desmin, and CD68.
Type IV collagen and
laminin (Fig. 3B) were detected along the cords or whorls of the
tumor cells, similar to the staining pattern of the
diastase-PAS reaction. Schwann cells and axonal components, immunoreactive for
S100 protein and neurofilament, respectively, were focally detected just adjacent to the cords or whorls, although the
tumor cells per se did not express these
proteins. Consequently, the
tumor was found to be perineurial in origin and was diagnosed as cutaneous sclerosing
perineurioma.