Skull-based giant cell tumor with atypical location highlighting the importance of intraoperative cytological examination: Report of four cases
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.241407
Source of Support: None, Conflict of Interest: None
Giant cell tumors (GCTs), also known as osteoclastomas, are rare primary bone tumors comprising 5% of all bony tumors. They mainly originate in the epiphyseal region of long bones of the extremities. GCTs of the skull base are extremely rare and were first described by Echols et al., in 1945. However, since then, only a few case series and individual cases have been reported.,,, In the skull, GCTs usually involves temporal and sphenoid bones. Skull-based GCT are locally aggressive with an uncertain behavior and outcome. Complete surgical resection is very difficult and challenging due to the complexity of accessing their location. Their clinico-radiological presentation is markedly variable and a preoperative diagnosis may be missed. However, an intraoperative frozen section/squash smear certainly helps in their diagnosis leading to the maximum possible resection and in preventing local recurrence. The role of chemotherapy and radiotherapy is questionable. Here, we report four cases of skull-based GCT with a detailed review of literature and highlight the importance of establishing the intraoperative tissue diagnosis.
A 15-year old young female patient presented with complaints of left-sided neck pain radiating to the whole head along with progressive neck deviation for 5 months. The symptoms were further complicated by the development of hoarseness of voice, difficulty in swallowing, nasal regurgitation of fluids, restriction of tongue movements, and inability to clear the food bolus. A history of diplopia was also elucidated. On examination, the 8th cranial nerve examination by Rinne's test revealed bone conduction more than air conduction, and the Weber's test was lateralized to the right ear. Absolute bone conduction was impaired on the left side signifying gross sensorineural hearing deficit in the left ear. Examination of the 9th, 10th, and 11th cranial nerves showed bilateral palatal drop and sluggish palatal movements with deviation of the uvula.
Magnetic resonance imaging (MRI) of the brain revealed a large lytic lesion with heterogenous enhancement, occupying the clivus, the basiocciput including bilateral occipital condyles, and the left petrous apex. The tumor was extending antero-inferiorly into the nasopharynx, posteriorly into the prepontine cistern, inferiorly upto the foramen magnum, and laterally on the left side into the inner table of the occipital bone, causing obliteration of the foramen lacerum, jugular foramen, hypoglossal canal, and internal acoustic meatus [Figure 1]a.
A 32-year old male patient presented with chief complaints of progressively enlarging swelling of the left temporal region for the past 18 months. The swelling measured 4 × 3 cm and extended between the lateral canthus and the tragus. It was firm, nonfluctuant, noncompressible, and fixed to the underlying bone. MRI showed lytic destruction of the left temporal bone and the floor of intracranial fossa with associated large T2-weighted hyperintense soft tissue component and heterogeneous post-contrast enhancement. Intraoperatively, the tumor was brownish-red, highly vascular with a variegated appearance, and invading the middle ear [Figure 1]b. Contrast-enhanced computed tomography (CECT) revealed an expansile lytic lesion with septations within the left temporal bone, encroaching upon the left temporal fossa [Figure 2]a. A subtotal resection was performed.
A 38-year old male patient presented with complaints of headache and painful swelling of the right upper face, anterior to the ear, since 1 year. No history of trauma or other associated symptoms such as vertigo, hearing loss, or seizures were present. On examination, the swelling was well-defined, firm, non-fluctuant, fixed to the underlying bone, and not moving with jaw movements.
MRI showed an ill-defined lobulated mass with a heterogenous signal intensity in the right infratemporal region, appearing predominantly isointense to muscles on T1-weighted and hypointense on T2-weighted images [Figure 1]c. The mass was involving the pterygoid and temporalis muscles and the right ramus of mandible, causing destruction of the skull base and zygomatic arch with extension into the middle cranial fossa. It showed a moderate homogenous contrast enhancement [Figure 2]b. Complete excision of the mass was done through the maxillary swing approach.
A 28-year old female patient presented with complaints of headache and gradually progressive diminution of the left eye vision for 5 months. MRI showed a 5 × 3 × 3 cm homogenously enhancing mass in the tuberculum sellae region. The mass was infiltrating anteroinferiorly into the ethmoid sinus, sphenoid sinus, and left orbital apex, and posteriorly into the pituitary fossa with compression of the optic chiasma. Intraoperatively, the tumor was firm, pinkish, and moderately vascular with well-defined margins and encircling the left optic nerve as well as eroding the sphenoid bone. A subtotal resection of the tumor was performed.
Intraoperative cytology: Frozen section/squash smear examination was performed in three cases. The smears were richly cellular and showed sheets of mononuclear cells intermingled with numerous osteoclast-like giant cells [Figure 3]a. Mononuclear cells were round-to-oval with focal spindling, vesicular chromatin, moderate amounts of vacuolated/bubbly cytoplasm, and indistinct cell borders. In addition, one case also showed hemosiderin pigment [Figure 3]b.
Histological examination [Figure 4]a-d]: Tissue sections were processed in 10% buffered formalin, and 5 μm sections were obtained for hematoxylin and eosin stains as well as special stains. All cases showed a relatively similar morphology. The tumor comprised sheets of mononuclear and many interspersed giant cells. The cells were round-to-oval with focal spindling, vesicular chromatin, prominent nucleoli and eosinophilic cytoplasm. Osteoclast giant cells contained 5–25 nuclei with a similar morphology as mononuclear cells. Two cases also showed extensive hemosiderin pigment deposition in both mononuclear and giant cells. Few mitotic figures and occasional lymphocytes and plasma cells were noted. In addition, area of hyalinization, necrosis, and sheets of foam cells were noted in individual cases.
GCTs of the skull base are exceedingly rare and commonly occur in young patients without any gender predilection. They preferentially involve the sphenoidal and temporal bones in the skull base region. This may be explained by the fact that their developmental mechanism is similar to that of long bones through an enchondral ossification, whereas other skull bones are formed by intramembranous ossification.
Three of our cases had an unusual location (case 1; clival, case 3; infratemporal, case 4; sellar), leading to an erroneous radiological diagnosis of a chordoma and a pituitary macroadenoma in case 1 and case 4, respectively. Although a few cases of clival GCTs have been reported, to our knowledge, no case primarily arising from the tuberculum sellae has been published till date.
They most commonly present with headache, accompanied by other symptoms, depending on the tumor's extension and infiltration of the cranial nerves. Of the four cases, two presented with headache and visual abnormalities and two as temporal region swelling. The tumor in Case 1 and Case 4, respectively, involved the 8th and the 2nd cranial nerves. Two of the tumors extended to involve the middle ear. Gross total resection was possible only in Case 3, whereas in the remaining cases, due to the large and complex tumor mass and encasement of multiple vital structures, a subtotal resection was performed.
Giant cell lesions show an overlapping of radiological features and an accurate preoperative diagnosis may not always be possible. Various radiological and histological differential diagnoses considered for these skull-based GCTs are giant cell reparative granuloma (GCRG), aneurysmal bone cyst, fibrous dysplasia, osteoid osteoma, osteosarcoma, Langerhans cell histiocytosis, brown tumor of hyperparathyroidism, chordoma, meningioma, and pituitary adenoma. On T2-weighted MRI images, very low signals are characteristic of GCTs and are proven to have a high diagnostic utility.,,, However, GCRGs may also show similar features due to hemosiderin deposition. These low signals are explained by the hemosiderin pigment deposition and callus formation due to the occurrence of pathological fracture.,, This is particularly more common in the temporal bone GCT. Zhang et al., in a review of 94 cases as well as their own series of 18 cases, reported markedly low signal on T2-weighted images in all the cases of temporal GCT, whereas the same findings were noted in 33% of the sphenoidal lesions.
Complete surgical excision is the treatment of choice; however, their complex location poses a great barrier. Thus, an accurate intraoperative tissue diagnosis is essential so that the surgeon may ensure an adequate surgical removal of the tumor. Zhang et al., in their review, reported a 100% 5-year overall- and event-free survival in all patients who underwent gross total resection, with or without postoperative radiotherapy (RT). Though the role of RT is controversial, it results in a better outcome in GCTs with subtotal resection. The role of chemotherapy has not been established for skull-based GCTs.
To conclude, skull-based GCTs are very rare and when located at unusual sites, mimic other common lesions. Thus, they pose a challenge while an attempt to establish an unequivocal preoperative diagnosis is being made. An intraoperative frozen section/squash smear report is important for confirmation of the diagnosis and may lead to a wider/complete excision, thus decreasing the chances of recurrence.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]