A rare case of giant soft tissue chondroma of the wrist: A cytopathological study with review of the literature

Abstract

Giant soft tissue chondromas (STCs) of the wrist are seldom encountered in clinical practice. Precise diagnosis of benign STC may pose diagnostic difficulties on clinical and radiological findings alone. We encountered a slowly growing soft tissue neoplasm in the radial aspect of the wrist joint of the right hand in a 52-year-old male, masquerading as a calcified hematoma, as suggested by magnetic resonance imaging. On cytohistopathological examination, it turned out to be a rare giant STC. The variable cellularity, in conjunction with cellular immaturity and atypia, could mislead one to a malignant pathological interpretation. Diagnosis is based on both radiological and cytohistological evaluation, which is indispensable for determining the tumor type. The detailed clinical, radiological, cytomorphological, and immune-histopathological study was carried out, which has prompted us to report this case along with a review of the literature.

Introduction

Soft-tissue cartilaginous tumors are relatively uncommon. The rare extraskeletal soft tissue chondromas (STC), also referred to as chondroma of the soft parts, is a benign soft tissue tumor composed mainly of a hyaline cartilage with no connection to the bone or periosteum.[1] Patients with a soft tissue chondroma may present to a dermatologist, surgeon or an orthopedician with a complaint of a hard nodule growing below the skin. Soft tissue chondroma should be considered in the differential diagnosis of any slowly growing mass of the wrist joint.

Case Report

A 52-year-old male patient presented to the Surgery Outpatient Department, with a well-defined, firm-to-hard, immobile, nontender, subcutaneous swelling over the lateral aspect of the wrist joint of the right hand, since two years. The swelling had gradually increased to the present size of 5 × 4 cm. It was not attached to the overlying skin. There was no restriction of movement of the fingers or wrist joint. There was development of mild pain recently, only when he lifted weight with his right hand. There was a history of trauma at the site six months prior. He was a known case of hypertension, on treatment since three years. The systemic findings were noncontributory.

The radiograph findings were unremarkable, except for few areas of calcification. Magnetic resonance imaging (MRI) of the right wrist and hand showed a well-defined, lobulated lesion measuring 5 × 4 × 3 cm in the radial aspect of the wrist, appearing T2 hyperintense, with a peripheral T2 hypointense rim, slightly hyperintense on T1 W1, with a central hypointense area, with no significant post-contrast enhancement [Figure 1a]. The lesion was closely abutting the scaphoid and trapezoid [Figure 1b]. Erosions were noted in the lunate. The MRI findings were suggestive of chronic infective arthritis with a differential diagnosis of myositis ossificans and chronic calcified hematoma.

Figure 1.

MRI right wrist and hand: (a) Well-defined lobulated lesion measuring 5 × 4 × 3 cm in the radial aspect of the wrist, appearing T2 hyperintense, with a peripheral T2 hypointense rim, slightly hyperintense on T1 W1 with a central hypointense area, with no significant post contrast enhancement; (b) the lesion was closely abutting the scaphoid and trapezoid. Erosions were noted in the lunate. FNA: (c) predominantly chondromyxoid substance showing chondrocytes (c) inset showing chondrocytes with mild atypia. (H and E, ×400), (d) showing clusters ofchondrocytes with vesicular nucleus and moderate amount of basophilic nucleus (H and E, ×400)

Fine needle aspiration (FNA) performed on the lesion showed predominantly cartilaginous tissue fragments with abundant chondromyxoid substance [Figure 1c]. The fragments showed chondrocytes with mild atypia [Figure 1c]. No binucleation or mitosis was noted. The background showed numerous red blood cells [Figure 1d]. Taking into consideration the clinical, radiological, and cytological findings, a diagnosis of soft tissue chondroma was considered. Extraskeletal, well-differentiated chondrosarcoma was kept as a close differential diagnosis.

Subsequently the swelling was excised and sent for histopathological examination. Intraoperatively it was noted that the swelling was well-demarcated from the surrounding tissues. Postoperatively the patient was disease-free with no evidence of recurrence for six months.

On gross examination, the swelling was 5 × 4 × 3.5 cm, well-defined, lobulated, hard, and glistening white [Figure 2a]. On cut section, white firm areas were noted [Figure 2b].

Figure 2.

Macroscopic features of the tumor: (a) External surface, the swelling is 5 × 4 × 3.5 cm, well-defined, lobulated, and glistening white. (b) On cut section white firm areas noted. Microscopic details of tumor: (c) Lobules of mature hyaline cartilage seen. The chondrocytes show mild cytological atypia and areas of myxoid change (H and E, ×100), and (d) calcification noted (H and E, ×100)

On microscopic examination, a well-defined lesion composed of lobules of mature, and at places, immature hyaline cartilage was seen. The chondrocytes showed mild cytological atypia. At the periphery focal myxoid areas [Figure 2c] were seen, with spotty calcification and small areas of enchondral ossification [Figure 2d]. No binucleation or mitosis was noted. A diagnosis of soft tissue chondroma was confirmed.

Immunohistochemical analysis showed nuclear and cytoplasmic immunoreactivity for S100 by the tumor cells. The Ki 67 index was less than one percent, confirming its benign nature.

Discussion

The extraskeletal soft tissue chondroma is a relatively rare, slowly progressing benign tumor. Its incidence, as mentioned in one study, is 1.5%.[2] It was first reported by Baumuller, in 1883.[3] In 1887, Paget reported that soft tissue cartilaginous tumors are usually benign.[3] Few have suggested the origin from the synovial sheath of the long tendons, the paratendinous soft tissues or the para-articular tissues.[4] Others consider them to be developmental faults or metaplasia.[3] Repeated trauma is also implicated as an initiating factor.[4] Intra-articular chondromas, juxtacortical chondromas, and chondromas of soft parts are the three types of extraosseous chondromas.[3]

Most STCs have been found to occur around the ages of 30 and 60 years.[4] The most affected site was the fingers (49%), followed by the hands (15%), toes (11%), feet (10%), forearms (4%), and others.[5] In our case the swelling was seen in a 52-year-old male and was situated on the radial aspect of the wrist joint. Most of the STCs described in literature are less than 3 cm in size.[3] In our case, the swelling was 5 × 4 × 3.5 cm in size. It is worth mentioning that in our case the tumor was at a relatively uncommon site and had a large size, which could hinder arriving at an appropriate diagnosis. Clinically the differential diagnosis should include a ganglion, giant cell tumor of the tendon sheath, fibroma, myositis ossificans, osteochondroma, calcinosis cutis, and chondrosarcoma.[4,6] However, radiological and cytohistopathological findings are necessary for definitive diagnosis.

Radiologically, MRI is the method of choice for evaluating this rare clinical entity. It defines the extent, the contour, the shape, and the intensity of the tumor in relation to the surrounding structures and calcifications, if any.[4] Extraskeletal chondromas usually show intermediate signal intensity on T₁-weighted images and high signal intensity on T₂-weighted images, in most MRI studies. The high signal intensity is due to the high water content of the cartilage.[6] However, the water content and degree of calcification can differ causing diagnostic difficulties.[6] In our case the differential diagnosis of chronic calcified hematoma and myositis ossificans was suggested by the radiologist.

It is important to note that only two cases have been reported in the literature, to have undergone FNAC for soft tissue chondroma, to determine the diagnosis preoperatively.[4,7] The cytological features of soft tissue chondroma mimic those of its malignant counterpart to a considerable extent. Awareness of the cytological features, that is, cellular fragments, chondrocytes showing no or little atypia, and absence of mitosis and binucleation, combined with the clinical and radiological findings, should guide the cytopathologist to make a correct diagnosis of this neoplasm.[7]

Positive diagnosis is provided by a histopathological examination. Histopathologically, the differential diagnosis of soft tissue chondroma includes other cartilaginous lesions such as true cutaneous chondromas, hamartomas, calcifying aponeurotic fibroma, skeletal tumors with cartilaginous differentiation (osteochondroma, synovial chondromatosis), chondroid syringomas, extraskeletal well-differentiated chondrosarcoma, and cutaneous metastases of chondrosarcoma or chondroblastic osteosarcoma.[8]

The histopathological appearance of this neoplasm ranges from an immature pattern dominated by chondroblasts (resembling osseous chondroblastoma) to a mature profile with chondrocytes (resembling osseous enchondroma).[3] The matrix can be hyaline, fibrous or fibrohyaline with granuloma-like areas in the stroma. The variable cellularity along with cellular immaturity and atypia could mislead one to a malignant pathological interpretation.[3] However, a soft-tissue chondroma is unlikely to display cords of tumor cells within a myxoid matrix, as found in the extraskeletal myxoid chondrosarcoma or the primitive round-cell pattern. Furthermore, hemangiopericytoid vascularity is characteristic of the extraskeletal mesenchymal chondrosarcoma.[3]

In our case, an extraskeletal, well-differentiated chondrosarcoma had been excluded by the presence of slow growth clinically, absence of secondary bone involvement and irregular calcification radiologically, and absence of binucleation and mitotic figures cytohistopathologically.[3,9] Calcification is seen in 33-70% of extraskeletal chondromas.[3] Diagnostic errors can be avoided if any soft tissue lesion that cannot be diagnosed is regarded as potentially malignant, until proven otherwise.[5]

Besides a histopathological examination, immunohistochemistry is useful in the diagnosis of STC, as the tumor cells are positive for the S-100 protein and vimentin and negative for epithelial and myoepithelial cell markers.[8] Ki 67 negativity confirms the benign nature of the tumor.[9]

Malignant transformation has not been reported yet. However, recurrence is a potential problem.[8] To prevent local recurrence it is advisable to remove the tumor completely, including the capsular structure and adhesion sites.[8]

Our experience with the present case highlights the significance of detailed clinical, radiological, and cytohistological analysis in soft tissue lesions of the wrist, with an unusually large size. STC should be considered in patients with a slowly growing, mildly painful, cutaneous nodule in the wrist. One should also understand the importance of recognizing benign soft tissue chondroma in spite of it exhibiting atypical features, such as pleomorphism and binucleation, cytopathologically.