Soft tissue chondromas or extraskeletal chondromas are benign soft tissue tumors of hyaline or myxoid cartilage originating in extraosseous and extrasynovial locations commonly found in the hands and feet.
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Epidemiology
Soft tissue chondromas are rare. They are most commonly seen in middle-aged individuals with men being more frequently affected than women 1-4.
Diagnosis
The diagnosis of soft tissue chondroma is established histologically 1.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:
soft tissue tumor consisting of lobules of well-defined cartilage
hyaline or myxoid matrix
limited chondroid cell atypia and mitotic activity
Clinical presentation
The most frequent presentation is a slow-growing firm painless and occasionally tender soft tissue mass 1,2.
Pathology
Soft tissue chondromas are soft tissue tumors with a chondroid matrix composed of hyaline or myxoid cartilage which sometimes calcifies 1-4.
Etiology
The etiology is unknown 1.
Location
The vast majority of soft tissue chondromas are found in the fingers (about 80%) 1,2. Other locations include hands toes and feet and uncommonly in the trunk or head and neck region. They have been rarely described in the skin, dura, lip or tongue 1-5.
Subtype
There is a single subtype the chondroblastoma-like soft tissue chondroma
Macroscopic appearance
Soft tissue chondromas are usually well-demarcated nodular soft tissue masses of grey-white-bluish color. Most tumors are small when they are detected, which might be due to their favorite location 1.
Microscopic appearance
Microscopically soft tissue chondromas are characterized by the following features 1:
hyaline and myxoid matrix outlined by fibrous septa
clusters of large chondrocytes floating in myxoid
fine calcifications or possibly endochondral ossification
limited mitotic activity and no abnormal mitotic figures
variable infiltrates of histiocytes
Genetics
Soft tissue chondromas are associated with FN1 gene rearrangements 1,6.
Radiographic features
Typical imaging findings are the following 1:
well-delineated lesion
separated from bone
ring-like or spiculated calcifications
MRI
On MRI soft tissue chondromas feature a lobular and heterogeneous appearance with the following signal characteristics 1,3-5:
T1: hypo to isointense compared to muscle
T2: hyperintense
T1 C+ (Gd): variable patterns of enhancement
Radiology report
The radiological report should include a description of the following:
form, location and size
tumor margins and transition zone
relations to the bone and muscular fascia
relation to neurovascular structures
Treatment and prognosis
Standard treatment of soft tissue chondromas usually consists of marginal resection, they can recur in about 15-20% of cases 1,3.
History and etymology
Cartilaginous tumors affecting soft parts, in general, have been already mentioned by the English surgeon James Paget in 1870 in his lectures on surgical pathology 7. An ossifying chondroma of the soft skullcap has been described by the German surgeon, B. Baumüller in 1883 2,8.
Differential diagnosis
Conditions that can mimic the presentation and/or appearance of soft tissue chondroma include 1-5:
synovial chondromatosis: association with the synovium
juxtacortical chondroma: features an attachment to the bone
soft tissue chondrosarcoma: greater cellularity, cytological and mitotic atypia
synovial bursitis
acral fibromyxomas: usually no calcifications
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