Chondromyxoid fibroma of the temporal bone: A rare entity.

Chondromyxoid fibroma (CMF) is the least common benign tumor of the cartilaginous origin. It is very unusual to find these tumors in the skull bones. We report one such case involving the temporal bone. Till date, only nine such cases including this patient, involving the temporal bone have been reported to the best of our knowledge. Grant Medical College and Sir J.J Group of Hospitals, Byculla, Mumbai, Maharashtra, India. A 12-year-old female patient presented with a history of headache associated with left earache of 1 month duration. This was followed by swelling over the left preauricular region 15 days later. Imaging was suggestive of an expansile lesion involving the squamous part of the left temporal bone with calcifications suggestive of a benign chondroid lesion. The patient was operated upon with left temporal incision and complete excision of the lesion. The patient had relief from headache, earache and swelling, with no evidence of new neurological deficit in the post-operative period. CMF of the skull bone is an extremely rare tumor. Differential diagnosis should be kept in mind, especially in cases of calcified lesions and includes chordoma, chondroid chondroma, and low-grade myxoid chondrosarcoma. En-bloc complete excision should be the aim to achieve cure.

Introduction

Chondromyxoid fibroma (CMF) is a slow-growing, rare, benign primary cartilaginous bone tumor. It was first described by Jaffe and Lichtenstein in 1948.[1]

CMF represents 0.4%-0.5% of all the primary bone tumors.[2] The most common site of origin is the lower extremity around the lower end of femur and upper end of tibia. Involvement of the skull bones is extremely rare. Till date, only nine such cases including this patient, involving the temporal bone have been reported in the literature. We report one such case elaborating the clinical presentation, radiological features, and histopathological findings.

Case Report

Case

A 12-year-old, right-handed, female patient was admitted with complaints of gradual-onset headache of 1 month duration. Initially, her headache was generalized, but later on, it was localized in left temporal region. It was mild to moderate in intensity, not associated with vomiting and no other aggravating and relieving factors. It was associated with pain in the left ear of 1 month duration, the pain was continuous, dull-aching in nature, and not associated with fever, ear discharge, or diminished hearing in the left ear.

The patient also gave a history of painful swelling over the left preauricular region of 15 days’ duration. Swelling was initially about the size of a lemon which had gradually increased over a period of 15 days to the present size of an apple. There was no redness or discharge from the swelling. There was no history of trauma at the site of swelling. There was no difficulty in chewing from left side of the jaw.

On examination, higher mental functions were normal. Cranial nerve examination was normal. Power was 5/5 in both the lower limbs. The sensations were intact. Reflexes were normal in both lower limbs and plantars were down-going bilaterally. On local examination, there was a 4 cm × 3 cm-sized swelling over the left temporal and zygoma in the left preauricular region. The swelling was hard, lobular, and tender on palpation. The swelling was non-pulsatile and there were no scars, sinuses, or dilated veins over the swelling. There was no difficulty in chewing or jaw movements on the left side.

X-ray of the skull [Figure 1] was suggestive of a multilobulated radiolucent lesion with well-defined margins in the left temporal region.

Figure 1

X-ray of the skull was suggestive of a multilobulated radiolucent lesion with well-defined margins in the left temporal region

Computerized tomography (CT) scan [Figure 2] revealed an expansile mass about 4.1 cm × 3.2 cm in size, arising from the left temporal region in the floor of the middle cranial fossa. It showed isodense, soft tissue within and also showed small calcific foci suggestive of chondroid neoplasm.

Figure 2

Computerized tomography scan showing a lesion about 4.1 cm × 3.2 cm arising from the left temporal region. It shows isodense soft tissue within and also shows small, calcific foci

Magnetic resonance imaging (MRI) scan [Figure 3] showed 4 cm × 3.7 cm × 4.4 cm-sized lobulated expansile mass in the squamous part of left temporal bone. Cortex was well maintained with no intracranial extension. The lesion was hypointense on T1-weighted images, isointense on T2 FLAIR, and heterogeneously hyperintense on T2-weighted images with strong heterogeneous post-contrast enhancement with non-enhancing areas within.

Figure 3

Magnetic resonance imaging scan showing a lobulated mass in the squamous part of the left temporal bone. Cortex is well maintained with no intracranial extension. The lesion shows heterogeneous enhancement on post gadolinium contrast images

The patient was operated by left temporal curvilinear incision with complete excision of the lesion along with a 5 mm-margin of surrounding normal bone. The tumor was well circumscribed along with thinning of the adjacent temporal and zygomatic bone. The tumor was firm in consistency and grayish white in color.

On histopathological examination [Figure 4], tumor cells could be seen arranged in a lobular pattern. Individual lobules show central hypocellular and peripheral hypercellular areas comprised of sheets of chondrocytes and stellate cells interspersed within a chondromyxoid background. There was no evidence of mitosis. The periphery of the lesion showed capillary proliferation with numerous, dilated, cystic spaces. Focal areas of dense calcification were also seen suggestive, of CMF.

Figure 4

On histopathological examination, tumor cells can be seen arranged in a lobular pattern. Individual lobules show central hypocellular and peripheral hypercellular areas comprised of sheets of chondrocytes. Focal areas of dense calcification are also seen, suggestive of chondromyxoid fibroma

Post-operatively, the patient was relieved from her headache, left-ear pain, and swelling with no new neurological deficit. Post-operative CT scan [Figure 5] showed complete excision of the tumor.

Figure 5

Post-operative computerized tomography scan showing complete tumor excision

There has been no recurrence till the recent follow-up.

Discussion

CMF is a rare, slow-growing, benign tumor of cartilaginous origin and was first described by Jaffe and Lichtenstein in 1948.[1] It represents 0.4%-0.5% of all primary bone tumors.[2] The most common site of involvement is the metaphysis of the long bones, especially around the knee joint, with the involvement of the skull bones being extremely rare.[3] In the skull, CMF develops from the cartilage or embryonic rests of cartilaginous tissue, which can be entrapped at the sites of sutures or skull base during the process of endochondral ossification.[4] The most common age groups affected are those in the second and third decades of life, with a predilection for males.[35] Our patient falls in the common age group, but differs as far as gender is concerned.

The clinical presentation varies according to the site of origin. The common clinical presentation in cases of skull-bone involvement are headache with bony swelling as in our case, others include neuralgia, facial pain, exophthalmos, convulsions, and diplopia.[6]

The imaging features of these lesions are characteristic. X-ray shows radiolucent lesion with well-defined margins.[7] CT scan shows osteolytic lesion with a sclerotic margin with foci of calcification.[46]

MRI images show a hypointense lesion on T1-weighted, hyperintense on T2-weighted images with intense contrast enhancement.[289] In the present case, most of the characteristic features were present on imaging.

The differential diagnosis [Table 1][4610-13] includes chondrosarcomas, fibrous dysplasia, chondroblastoma, enchondroma, and chordoma.[4610] Chondrosarcoma can be differentiated from CMF by it's invasive pattern of growth and presence of mitosis. Some chondrosarcomas can have peripheral lobularity which makes it difficult to differentiate them from CMF. Presence of a well-formed hyaline matrix and absence of fibrous component are other features distinguishing chondrosarcomas from CMF. Immunohistochemistry is not helpful because both of these tumors express the S-100 protein.[11] Chondroblastoma is another benign tumor with cartilaginous differentiation. Histologically, it consists of sheets of stromal cells, multinucleated giant cells, and eosinophilic chondroid matrix. Fetal chondroblasts are distinctive and consist of abundant cytoplasm, with distinct cytoplasmic membranes. The “fried-egg appearance” due to the location of the nuclei in the centre is characteristic. These cells stain positive for S-100 immunohistochemically.[410-13]

Table 1

Histopathological features of lesions mimicking chondromyxoid fibroma

The definitive management of such tumors is “en-bloc” surgical resection[478] with resection of a portion of the surrounding normal bone to prevent recurrences and malignant conversion. As in our case, we had achieved complete resection of the tumor with a portion of the surrounding normal bone. High-dose irradiation is recommended in cases of incomplete resections due to the location of the tumor.[611] They combined treatment with proton beam to minimize acute and late side-effects.[8]

The rate of recurrences varies between 3% and 26% with an interval of 5 months to 10 years.[67] Our case did not have any recurrence till the recent follow-up of 6 months.

Conclusion

CMF is a benign, slow-growing cartilaginous tumor. Involvement of the temporal bone of the skull is extremely rare. Differential diagnosis should be kept in mind, especially in cases of calcified lesions and includes chordoma, chondroid chondroma, and low-grade myxoid chondrosarcoma. En-bloc complete resection should be the aim to achieve cure. Post-operative radiotherapy may be required for incomplete resections.