Chordoma of petrosal mastoid region: A case report.

BACKGROUND: Chordoma is a rare low-grade malignant tumor originating from embryonic notochordal tissue mainly occurring in the axial bone, mostly in the spheno-occipital junction and sacrococcyx, which accounts for approximately 1% of all malignant bone tumors and 0.1%-0.2% of intracranial tumors. Chordoma in the petrous mastoid region is rare. CASE
SUMMARY: We describe a 36-year-old male patient with chordoma in the left petrous mastoid region. The main clinical manifestations were pain and discomfort, which lasted for 2 years. Magnetic resonance imaging showed a lobulated mass in the left petrous mastoid with an unclear boundary and obvious enhancement. The tumor was completely removed after surgical treatment, and a histological examination confirmed that the tumor was a chordoma. During 5 years of follow-up, no clinical or radiological evidence of recurrence or metastasis was found.
CONCLUSION: Chordoma in the petrosal mastoid region is rare but should be included in differential diagnosis of petrosal mastoid tumors. ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.

Core Tip: Chordoma is a rare disease, especially in the petrous mastoid region. Its imaging findings have rarely been reported, and an understanding of its magnetic resonance imaging findings is lacking. However, in the differential diagnosis of petrous mastoid tumors, chordoma should be considered, especially when lobulated masses are found.

INTRODUCTION

Chordoma is a rare low-grade malignant tumor originating from embryonic notochordal tissue with an incidence of less than 0.1/100000 individuals per year[1]. Chordoma is locally destructive and easily invades important structures, such as bones, nerves, and large blood vessels. Chordoma is likely to relapse after resection, but metastasis is rare. The pathogenesis of chordoma is unclear, and the disease is speculated to originate from residual cells of the notochord that develop during fetal development. The tumor usually occurs in the axial bone, especially at both ends. Most chordomas in the head and neck occur in the spheno-occipital junction, accounting for almost 35% of all chordomas[2]. A few cases occurring in the nasopharynx, paranasal sinuses, oropharynx, and jugular foramen have been reported[2,3], and approximately 0.2% of the cases reported in the literature occurred in the jugular foramen region[4] but not the petrosal mastoid region. Here, we report a case of chordoma in the left petrosal mastoid region with intracranial expansive growth resulting in cerebellar compression and deformation. The main clinical manifestation was a 2-year history of temporal pain and discomfort.

CASE PRESENTATION

Chief complaints

A 36-year-old man visited our hospital in December 2014 because of left temporal pain.

History of present illness

In 2012, no obvious cause for his left temporal pain and left-sided headache could be identified, and the patient had no symptoms of hearing loss, dizziness, nausea, or vomiting and no obvious redness, swelling, heat, pain, or structural aberrations in the adjacent skin.

History of past illness

The patient had a history of hepatitis B infection for > 30 years, and his liver function was normal.

Personal and family history

No specific genetic or family history of disease was identified.

Physical examination

Neurological examination revealed House Brackmann Grade II, gait disturbance, and tinnitus. The patient denied hearing loss and diplopia.

Laboratory examinations

No abnormality was found in the laboratory examination.

Imaging examinations

Magnetic resonance imaging (MRI) of the brain a lobulated mass in the left petrous mastoid region with a maximum interface of approximately 3.2 cm × 3.9 cm × 5.0 cm; surrounding bone absorption and destruction; uneven signal intensity on T2-weighted imaging (T2WI) (Figure 1A); isointensity and hypointensity on T1-weighted imaging (Figure 1B); hyperintensity on fluid-attenuated inversion recovery (Figure 1C); small cystic degeneration in the interior of the tumor (Figure 1A and B); and obvious enhancement of the solid components of the lesion on the contrast-enhanced scan (Figure 1D). No sign of involvement of the left jugular vein and left sigmoid sinus was observed. Left cerebellar compression and displacement were evident, but no brain parenchymal edema was noted.

Figure 1

Brain magnetic resonance imaging before surgery. A, B: T2-weighted axial images (A) and T1-weighted images (B) showed a lobulated mass (white thick arrow) in the petrous part and mastoid area of the left temporal bone, swelling to the brain, with isointense and hypointensity signal on T1-weighted images, hyperintensity and slightly hyperintensity signal on T2-weighted images , and there was a small cystic degeneration area inside (white fine arrow), the surrounding bone was damaged, and the left cerebellar hemisphere was compressed to deformation; C: Fluid-attenuated inversion recovery coronal magnetic resonance imaging (MRI) showed a mass with hyperintensity signal (white thick arrow), and the boundary was clear; D: T1-enhanced axial sequence showed uneven obvious contrast enhancement. There was no enhancement in the cystic degeneration area (white small arrow). Brain MRI at 5 years after surgery; E, F: T2-weighted axial images (E) and T1-weighted images enhanced (F) sequence showed postoperative changes in the left mastoid area, but no definite abnormal signs were found.

FINAL DIAGNOSIS

The gross specimen of the tumor was grayish-red and tough with a rich blood supply and had an unclear boundary. Microscopically, the tumor consisted of a dual cell population embedded in an abundant myxoid background. The cells were epithelioid polygonal in appearance with clear or eosinophilic cytoplasm, and a few mitotic cells were observed (Figure 2A). The immunohistochemical staining showed that vimentin, soluble protein-100 (S-100), epithelial membrane antigen (Figure 2B), and cytokeratin (CK)19 were positive, and CK staining was negative. The Ki67 antigen (Ki-67) fraction was approximately 1%. Ultimately, a diagnosis of chordoma was made.

Figure 2

Histological examination of chordoma. A: Epithelioid polygonal cells with clear or palely eosinophilic cytoplasm arranged in clusters and cords (hematoxylin and eosin, 100×). B: Immunohistochemical examination showed positive expression of epithelial membrane antigen (magnification 100×).

TREATMENT

The patient underwent microscopic tumor resection through the upper and posterior windows of the left ear. During the operation, the tumor was found to be located in the epidura; the petrous part of the temporal bone and the surface of the occipital bone were eroded by the tumor; the left transverse sinus was involved; and the lower part of the tumor surrounded the nerves and vessels.

OUTCOME AND FOLLOW-UP

The patient recovered well after surgery, no specific discomfort was mentioned, and he was discharged 1 wk after the operation. As chordoma is a low-grade malignant tumor, the patient was re-examined once a year after the operation, and no obvious abnormality was found after follow-up for 5 years (Figure 1E and F).

DISCUSSION

Chordoma is a rare, slow-growing, locally invasive malignant tumor originating from primitive notochordal tissues that develop longitudinally along the axis. Chordomas account for 3% of all primary bone tumors[5]. Approximately 50% of chordomas occur in the sacrococcyx, 30% of chordomas occur in the spheno-occipital region, and 20% of chordomas occur in the mobile spine[6]. Chordoma can occur at any age, and the most common age at diagnosis is 20–40 years. The gross specimen of the tumor showed lobulated and expansive growth with mucus, cystic necrosis, a small bleeding focus, calcification, ossification, and cartilage islands, which easily invaded the surrounding bone and caused extensive bone destruction. Histologically, the tumor was composed of droplet cells; the tumor tissue was divided into lobules by connective tissue; and the tumor cells were arranged into small clusters, flakes, strips, and acini with common degeneration and myxoid degeneration in the stroma. Histologically, chordoma appearance can be divided into the following three subtypes: classical, chondroid and dedifferentiated, and classical chordoma is the most common subtype. In addition, chondroid tumor growth is the slowest, and dedifferentiated tumor growth is the fastest.

Typical chordoma computed tomography (CT) findings mainly include: irregular low-density masses with well-defined boundaries; expansive growth, absorption and destruction of surrounding bone; irregular calcification inside the lesion; and obvious enhancement[7]. CT can accurately show bone and internal calcification but is insufficient for soft tissue analyses, and MRI is needed to facilitate further diagnosis.

The MRI findings of chordomas are diverse[8]. The typical MRI findings of chordomas in the clival region show obvious hyperintensity and a “beehive-like” appearance on T2WI, reflecting the histological characteristics of tumor tissue mainly composed of mucous stroma and droplet tumor cells secreting mucus. In this case, the presence of scattered strips and flakes with a low signal intensity suggested that the tumor was related to bone destruction, calcification, or a fibrous septum, and the high signal area in the tumor was separated and appeared beehive-like[9]. Enhancement of the chordoma on imaging is mainly inhomogeneous and obvious, while the dynamic enhancement scan shows continuous and slow enhancement, which is mainly caused by the adsorption of Gd-DTPA molecules to the mucin in the cell or cell interstitium, and the typical enhancement of chordoma shows a “honeycomb sign”[9]. In this case, the MRI findings differed from those of typical chordomas in the clival region. T2WI showed that the lesion was mainly slightly hyperintense with only narrow areas of hyperintensity. Given the pathological results, the low signal intensity on T2WI was likely due to the dense arrangement of tumor cells and scarcity of mucous cells. On the contrast-enhanced scan, the focus was not uniformly enhanced, the small cystic area was not enhanced, and the typical honeycomb sign was not observed.

Chordoma in the petrous mastoid region should be differentiated from the following tumors (Table 1): (1) Jugular glomus tumors also show osteolytic destruction with flaky calcification, marginal bone infiltration, and a “salt and pepper sign” on T2WI, while chordomas show a high signal intensity, small cystic degeneration and obvious enhancement on T2WI; (2) Most patients with middle ear cancer have a history of chronic suppurative otitis media, and symptoms, such as earache, tinnitus, and ear canal bleeding, may occur. The main manifestations on MRI are a soft tissue mass with the middle ear as the center, an unclear boundary, surrounding bone absorption and destruction, and enhanced inhomogeneous enhancement; in contrast, although chordomas show expansion and growth, the boundary is clear, and the enhancement is obvious; (3) Chondrosarcoma and chordoma have overlapping ages of onset, both feature calcification and surrounding bone infiltration in the mass, and T2WI can show a significantly high signal intensity. Thus, distinguishing between these two diseases relying solely on imaging features is difficult, and the final diagnosis depends on histopathology; and (4) Solitary fibroma tumor (SFT) is a borderline tumor, and most SFTs are considered benign and more common in adults than children. MRI mainly shows well-defined masses mostly in the supratentorial space that are primarily attached to the dura mater with an abundant blood supply and obvious enhancement; a specific sign of intracranial solitary fibroma is a hypointense area (collagen fibers) on T2WI. In most cases, empty blood vessels can be observed, and most adjacent bones show compressive changes, while chordoma has hyperintensity on T2WI, and the surrounding bone is absorbed and destroyed.

Table 1

Differential diagnosis of chordoma in the petrous mastoid region

Imaging	Chordoma	Jugular glomus tumors	Middle ear cancer	Chondrosarcoma	Solitary fibroma tumor
CT	Irregular low-density mass with calcification and well-defined boundaries, expansive growth, and the surrounding bone is absorbed and destroyed	Low-density mass, osteolytic destruction with flaky calcification	Soft-tissue density mass with ill-defined, surrounding bone absorption and destruction	Both feature calcification and surrounding bone infiltration in the mass	Soft-tissue density mass with well-defined boundaries, the most of adjacent bones show compressive changes
MRI	Obvious hyperintensity and a “beehive-like” appearance on T2WI, and honeycomb sign of obvious enhancement	A “salt and pepper sign” on T2WI, and significant enhancement	Soft tissue mass with the middle ear as the center, an unclear boundary, and enhanced inhomogeneous enhancement	Significantly high signal on T2WI, and inhomogeneous enhancement	Attached to the dura mater with, obvious enhancement, and hypointense area (collagen fibers) on T2WI

CT: Computed tomography; MRI: Magnetic resonance imaging; T2WI: T2-weighted imaging.

CONCLUSION

Chordoma occurring in the petrous mastoid region is rare, its imaging findings are rarely reported, and an understanding of its MRI findings is lacking. However, in the differential diagnosis of petrous mastoid tumors, chordoma should be considered, especially when lobulated masses are found. The T2WI results are mainly characterized by a high signal intensity, obvious enhancement, and surrounding bone absorption and destruction. Therefore, an imaging examination can sufficiently show the extent of the focus and surrounding involvement, which can provide more useful information for clinical treatment.

ACKNOWLEDGMENTS

We acknowledge Wang YJ and Huang C, Department of Radiology of Zhejiang provincial hospital of Chenese Medicine and No. 926 Hospital, Joint Logistics Support Force of PLA, for his special contribution to this case. We acknowledge the work of colleagues in the Pathology and Radiology Department in offering the original images and data related to this article.