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a 36-year - old woman with no history of any trauma exhibited a palpable mass on the volar ulnar aspect of her left middle finger at the level of the distal interphalangeal joint for a year .
physical examination revealed a 11.5-cm hard , non - tender , non - movable mass .
plain radiographs of the finger revealed a calcifying soft tissue mass associated with large cortical scalloping on the volar ulnar side of the distal phalanx ( fig .
the distal interphalangeal joint was normal in appearance . on the high - resolution ultrasound ( us )
exam ( hdi5000 , philips medical system , bothell , wa ) with a high - frequency ( 15 - 7 mhz ) compact linear transducer , a heterogeneously hyper - echoic mass with surface lobulation and extrinsic cortical erosion by the mass was clearly observable ( fig .
surgery revealed a flesh - colored lobulated mass was firmly attached to the periosteum of the distal phalanx and eroded it .
microscopic sections revealed a spindle - cell neoplasm with scattered calcifications and chondroid differentiation ( fig .
3 ) . a pathologic diagnosis of calcifying aponeurotic fibroma was made . during the last nine months
calcifying aponeurotic fibroma usually appears in the first decade of life and most of the lesions manifest within the first 2 decades of life . for this reason ,
the tumor has since been reported in the fingers , wrist , forearm , elbow , upper arm , neck , abdominal wall , lumbar paravertebral area , leg , ankle , and thigh ( 4 , 5 ) .
fibromatoses can be divided into two subdivisions , based on anatomic location and on age of presentation .
one is the " juvenile fibromatoses " including juvenile aponeurotic fibroma , congenital generalized fibromatosis , fibromatosis coli , fibrous hamartoma of infancy , recurring digital fibrous tumor of reye , juvenile hyaline fibromatosis , diffuse infantile fibromatosis , and hereditary gingival fibromatosis .
the second subdivision includes the aggressive fibromatoses , plantar - palmar fibromatosis , and nodular fasciitis ( 1 ) .
radiologically , calcifying aponeurotic fibroma may show a soft tissue mass with no associated osseous lesions and a fine stippling of focal calcification ( 4 ) .
however , in extremely rare cases , occasional scalloping of the cortex ( 1 , 3 ) and thickening of the bone ( 2 ) have been reported in pediatric patients . to our knowledge , there has been no case with involvement of the distal digital phalanx . on mri ,
kwak et al . ( 7 ) reported that the signal intensity of the calcifying aponeurotic fibroma was lower than that of muscle on t1- and t2-weighted images . in our case
, us also clearly demonstrated the extent and character of the soft tissue mass with internal calcific foci and cortical erosive changes of the adjacent bone .
the recurrence rate after surgical excision of this tumor is high and generally reported at 50% ( 8) . this necessitates an accurate diagnosis and complete excision .
therefore , evaluation of the extent of the mass and its relationship with surrounding soft tissue or bone is important .
the differential diagnosis of calcifying aponeurotic fibroma differs depending on the patient 's age , location of the lesion , presence of the calcification , and osseous involvement . calcifying aponeurotic fibroma in adults
should be differentiated from other fibrous tumors such as aggressive fibromatoses , plantar - palmar fibromatosis , and nodular fasciitis .
however , in this case , considering distal phalangeal erosive soft tissue mass with calcification , the differential diagnoses were parosteal / soft tissue chondroma , synovial sarcoma , and the calcified epidermoid . in summary , calcifying aponeurotic fibroma is a rare soft tissue tumor that presents as a painless mass primarily on the volar surface of the hands and plantar aspects of the feet in juveniles , but this tumor should be also included in differential diagnoses of any mass with calcification and adjacent bone involvement in the distal phalanx of the finger . in addition , us could be useful for the preoperative evaluation of digital calcifying aponeurotic fibroma .
calcifying aponeurotic fibroma is a rare soft tissue tumor that occurs in the distal extremities of children and adolescents . 
 we report ultrasound and x - ray findings of a calcifying aponeurotic fibroma in the finger of a 36-year - old woman , associated with distal phalangeal bone involvement .