INTRODUCTION

Soft tissue chondroma is a rare benign tumor which has a tendency to occur in the hands and feet. It affects both sexes equally and mainly occurs in patients aged 30 – 60 years.^1,2,3 Repeated micro trauma may be an initiating factor. It presents as a slowly growing mass, most commonly in the hands and feet.^1,4

It should be differentiated from benign tumors like ganglion cyst, myositis ossificans, pseudomalignant osseous tumor, ossifying fibromyxoid tumor, synovial chondromatosis, osteochondroma, or a malignant tumor like chondrosarcoma, extra skeletal osteosarcoma and synovial sarcoma.^5,6 Diagnostic errors can be avoided if any soft tissue lesion that cannot be diagnosed is regarded as potentially malignant until proven otherwise.^6,7

It arises from the synovial sheath of the long tendons, the paratendinous soft tissues or the para-articular tissues.^5,8,9

Extra-skeletal chondromas are composed of hyaline cartilage with focal calcification and can show worrying radiologic and histological pictures simulating chondrosarcoma.^10,11

MRI is the method of choice in the evaluation of this rare clinical entity. This tumor rarely evolves into a malignant tumor.^9,12,13

The clinical, radiological and cytological triad is important for the correct diagnosis of soft tissue chondroma despite worrying cell atypia.^14,15

Positive diagnosis can only be provided by the histopathological examination. Surgical treatment is the only successful solution but recurrence is not uncommon.^11,14,15

CASE REPORT

A 42 year old Egyptian male was presented to the surgical outpatient department (OPD) at Ghayathi hospital with a slowly progressive mass in the dorsum of his left foot of around 7 years duration. Initially, the swelling was painless until 4 months before he attended the OPD, when he started to feel increasing pain in his left foot on walking for long distances. The pain increased in intensity on wearing shoes. The patient had a mild tingling sensation in the dorsum of the first web space associated with mild difficulty in upward stretching of his left big toe. However, there was no history of trauma. Furthermore, family history and personal history were irrelevant. General clinical assessment was normal.

Figure 1: Hard, lobulated, nontender swelling on the left foot.

Locally, there was a hard, fixed, lobulated, nontender swelling on the dorsal aspect of the left foot. The swelling was 4x2 cm in size with well-defined borders. It was not attached to the overlying skin (Fig. 1). Distal circulation was normal but the dorsalis pedis was palpated with difficulty. Neurological examination showed mild hypoesthesia over the dorsum of the first web space.

Hematological and biochemical tests including CBC, ESR, LFTs, KFTs, and FBS were within normal limits.

An X-ray of the antero-posterior, lateral and oblique views showed a normal bony skeleton of the foot with no evidence of calcifications (Fig. 2).

Figure 2: An X-ray of the antero-posterior.

Ultrasound examination of the mass clarified a well defined soft tissue mass of around 3x2x2 cm in size. The mass had a thickened wall and a hypo-echoic center and it contained one or more hyper-echoic minute foci (Fig. 3).

Figure 3: Ultrasound examination of the mass.

MRI of the left foot before and after IV contrast showed a well circumscribed soft tissue mass with hypo-intense central zone. The mass was 3.4x2.3 cm in size with a lobulated surface. The mass was related to the extensor hallucis longus tendon and lying directly over the intermediate and medial cuneiform bones. The periosteum of the bones was intact.

Fine needle aspiration cytology (FNAC) of the mass revealed chondrocytes in a cartilaginous matrix with mild insignificant cellular atypia. The overall picture was suggestive of soft tissue chondroma (Fig. 4).

Figure 4: FNAC of the Mass.

Since the patient was suffering from left foot pain with progressive inability to wear his left shoe, he was scheduled for excisional biopsy of the mass under GA with exsanguination of the limb using A/K pneumatic tourniquet.

Intraoperatively, the mass was found to be hard, lobulated, grayish white situated under the inferior extensor retinaculum, in close proximity to the lateral surface of the extensor hallucis longus and close to the dorsal periosteum of the intermediate cuneiform bone.

The swelling was excised completely (Figs. 5 & 6). The patient had a smooth post-operative course and was discharged from the hospital on the second post-operative day in good general condition.

Figure 5: Excised contents of the swelling.

Figure 6: Disection of the Mass.

Histological assessment of the resected specimen confirmed a soft tissue chondroma characterized by chondrocytes in hyaline matrix with mild focal cellular atypia as shown in Fig. 7.

Figure 7: Histological assessment of the specimen

DISCUSSION

Soft tissue chondroma is a rare clinical entity. It has the following characteristic features: