Keywords
enchondroma - chondrosarcoma - malignant transformation
Introduction
An enchondroma is the most common benign bone tumor in hands, involving predominantly
phalanges. Its malignant counterpart, the chondrosarcoma, usually affects the pelvis,
proximal femur, and humerus, but it was not reported in the small bones of the hand.
Enchondromas rarely turn into chondrosarcomas. Although this transformation is more
frequent in multiple conditions than in solitary injuries, it is infrequent in hands.[1]
We present a case of malignant degeneration of an enchondroma at the middle phalanx
of the fourth finger of the left hand initially diagnosed with a simple radiograph.
Such malignant transformation was observed clinically and radiologically 2 years later,
and the anatomopathological diagnosis of chondrosarcoma was established.
Clinical Case
This is an 85-year-old male patient seen at the Plastic Surgery Clinic from Hospital
Universitario de Burgos, in Spain. An enchondroma at the middle phalanx of the fourth
finger of the left hand was diagnosed based on clinical findings and simple radiographs.
The radiological report described a well-defined expansive lytic lesion associated
with cortical erosion, soft tissue swelling with probable calcification, and reduced
bone density in the middle phalanx of the fourth finger of the left hand, all link
with focal osteopenia. This lesion was consistent with an enchondroma as first diagnostic
option. In addition, the radiological report described severe degenerative changes
at the medial and distal phalanx and the first carpometacarpal joint ([Fig. 1]) In view of radiological and clinical findings, a conservative treatment was instituted
due to the medical history of the patient (who had multiple conditions and a generalized
vascular compromise) and his advanced age.
Figure 1 Posteroanterior simple radiography showing the lesion diagnosed 2 years ago as an
enchondroma. The tumor was located at middle phalanx of the fourth finger and measured
in millimeters.
Two years later, the patient came for a visit due to a clinical change, with increased
pain and joint stiffness, but no cutaneous ulceration.
At the physical examination, the patient had a painful lesion with an external size
of 2.5 × 3 × 2 cm at the level of the medial phalanx and distal interphalangeal joint
of the fourth finger from the left hand. In addition, the lesion hindered the movement
of the affected finger. Since its radiological presentation ([Figures 2] and [3]) was consistent with a sarcomatous degeneration, a computed tomography (CT) and
biopsy were requested.
Figure 2 Posteroanterior simple radiography revealing an expansive lesion at the middle phalanx
of the fourth finger, with different size and shape but at the same location seen
2 years ago.
Figure 3 Oblique simple radiography showing an expansive lesion at the middle phalanx of the
fourth finger.
A multislice helical CT was performed in the left hand to complete the study of this
expansive, lytic lesion affecting the middle phalanx of the fourth finger of the hand.
The scan revealed cortical bone thinning, areas of cortical destruction, and small,
punctate calcifications within the lesion which were related to the chondroid matrix.
The approximate diameter of the lesion was 21 × 28 × 25 mm (anteroposterior, transversal,
and craniocaudal measurements, respectively). These findings suggested a protruding
enchondroma. Although protruding enchondromas appear aggressive, a sarcomatous degeneration
could not be ruled out because of the increased size of the lesion and the greater
cortical destruction when comparing radiographs taken in January 2011 and October
2013 ([Figure 4])
Figure 4 Helical computed tomography images revealing an expansive lesion at the middle phalanx
of the fourth finger of the hand (explanation in text).
These radiological findings led to lesion biopsy, which could not establish a histological
differentiation between a protruding condition and a low-grade chondrosarcoma.
After discussing the condition with the patient and his family, the surgical removal
of the lesion was decided, with amputation of the fourth finger of the left hand.
Pathological anatomy grossly described a lesion at a surgical resection piece measuring
6.8 cm at its longitudinal axis, 3.5 cm at its transversal axis and 3.4 cm at its
dorsoventral axis. The medial region of the piece presented a tumor measuring 4 cm
at its longitudinal axis per 3.5 cm at its transverse axis that ulcerates focally
on the external lateral surface. When sectioned, the tumor was white, elastic, smooth
and homogeneous, with white areas alternating with reddish brown areas, measuring
2.7 cm at its dorsoventral axis per 2.8 cm in its transversal axis. Microscopically,
it was a chondroid tumor, with nodular appearance and dense cellularity, atypical
cells with pleomorphic, hyperchromatic nuclei and frequent binucleation. In addition,
the tumor presented myxoid areas. Cortical bone disruption was observed in multiple
points, with infiltration of the adjoining soft parts in some areas. These histological
findings are consistent with a low-grade chondrosarcoma that does not contact the
resection margin. The study was carried out using formaldehyde fixation and decalcification
techniques.
The patient died 4 years after treatment with no signs of local recurrence or secondary
chondrosarcoma metastasis. Clinical history reported cause of death as an acute myocardial
infarction.
Discussion
We present the malignant transformation from a solitary enchondroma to chondrosarcoma.
This malignancy is extremely rare, with few cases recorded in the literature.
Enchondromas are the most common bone tumors in hands (90%), consisting in intramedullary
lesions characterized by a well-differentiated hyaline cartilage. Although infrequent,
its transformation into malignant entities must be considered. Malignancy transformation
rates are much higher in patients with multiple enchondromatosis, such as those with
Ollier disease or Maffucci syndrome. Some authors reported an up to 50% relationship
rate between chondrosarcomas and Ollier disease.[1]
Enchondromas arise from growth plates with failed cell hypertrophy and programmed
change processes, originating non-calcified columnar cartilage cells.
An enchondroma is usually diagnosed incidentally due to a fracture associated with
a regular trauma or in a radiological examination requested for another cause. This
tumor is indolent, slow growing and avascular, with no relevant perilesional inflammatory
response.[1] An enchondroma with enlarged width is called protruding enchondroma and a differential
diagnosis with chondrosarcoma is required.
The usual treatment for an enchondroma is curettage and defect filling with autologous
tissue or a bone replacement.
The skeletal chondrosarcoma family is a heterogeneous group of malignant mesenchymal
bone tumors characterized by chondroid matrix production. Primary chondrosarcomas
are often located in the pelvis, femur and proximal humerus, but are very rare in
hand bones, with a frequency of 0.5 to 3.2% of all chondrosarcomas. In addition, these
hand tumors present a low risk of either primary or secondary metastasis (1.8%) in
contrast to other locations (18%), and they are not life-threatening. Its small malignancy
potential relates to tumor biology. Its Ki-67 index (associated with the cell proliferation phase) is lower compared to other
locations; the same is true for p53.[2] Their location facilitates detection with a smaller size, allowing for radical treatment.
For hand chondrosarcomas, mean age at presentation (67 years old) is higher compared
to other locations, and there is a slight predilection for females. These tumors are
located in phalanx and metacarpal bones in 60% and 40% of the cases, respectively,
and present with cortical destruction and tissue extension.[2] The most affected finger is the 5th finger, whereas the least involved finger is the fourth finger, as in our clinical
case. In cases with distal phalanx compromise, the first finger is the most affected
one.
Secondary sarcomas may derive from isolated osteochondromas and multiple hereditary
osteochondromas, synovial chondromatosis, fibrous dysplasia, Paget disease, enchondromas,
and multiple enchondromatosis, such as Ollier disease and Maffucci syndrome; in addition,
they may arise after radiotherapy. Secondary chondrosarcomas account for approximately
1% of all malignant bone tumors.[3] Of all these pathological conditions, the most common precursor for chondrosarcomas
is osteochondroma, with a variable transformation incidence in revised series.
The malignant transformation of a solitary enchondroma is infrequently reported in
the literature. In 1990, Nelson[4] presented 18 cases described in the literature, but only those reported by Wu[5] and the author himself are considered good documentations of the radiographic and/or
histological transformation of an enchondroma into a chondrosarcoma. Subsequently,
other authors reported the transformation from an enchondroma in a chondrosarcoma
with years of radiological follow-up of a enchondroma, including with the development
of pulmonary metastasis.[6]
[7]
[8]
[9] Our case demonstrated radiologically the malignant transformation of an enchondroma
diagnosed in 2011 into a low-grade chondrosarcoma 2 years later at the same location.
Clinical and the radiological findings support the diagnosis of an enchondroma, although
an anatomopathological confirmation would be interesting now in view of the subsequent
evolution, because the radiological image of an initial chondrosarcoma can be confused
with an enchondroma.
Pain is an important symptom, reported in 90% of chondrosarcomas and 43.8% of enchondromas.
The medical history and radiological changes of pre-existing injury must also be considered.
Any change in an old lesion, including up to 40 years in evolution as described by
Wu, must be assessed remembering the potential malignant transformation of an enchondroma.
The size of an enchondroma may be an important factor in its malignancy. In lesions
ranging from 3 to 7 cm in size, there is a 2% to 3% of potential malignant transformation;
these figures rise to 5% in lesions with 8 to 15 cm in size. Logically, we can deduce
that a large enchondroma in the hand is uncommon because this is a very exposed location,
in which the growth of an injury would be noted, resulting in a medical attention.
The differentiation between a phalangeal low-grade chondrosarcoma and an enchondroma
is difficult for both pathologists and clinicians, with no well-defined criteria.
Despite the low metastatic potential of chondrosarcomas, this distinction is critical
because they require a more radical treatment than enchondromas. According to Welkerling,[10] the distinction between enchondromas and chondrosarcomas is not clearly defined,
but hand enchondromas present greater cellularity compared to other locations, with
enlarged, double nuclei. Some authors have suggested the differentiation of enchondromas
and low-grade chondrosarcomas using a DNA cytometric analysis of nuclear changes,
including nucleus size and polymorphism, always supported by clinical and radiological
findings.
Regarding treatment, radical excision is recommended since limited surgical procedures
result in a high recurrence rate for chondrosarcomas (up to 12.5%).[11] Conservative treatment in this location is difficult due to the proximity of hand
plans, which facilitate tumor extension to other compartments.
The amputation of the affected finger is the correct surgical treatment to avoid local
recurrence or distant metastasis. If this intervention is not carried out, a careful
follow-up of the patient is warranted.
As a conclusion, we must remember that enchondromas may evolve to malignant degeneration
in chondrosarcoma. Although unusual, there are some cases recorded in the literature,
and such transformation may be considered in our therapeutic action.
