Clinical, radiological, and pathological features of 24 atypical intracranial epidermoid cysts

Clinical article

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Object

Most intracranial epidermoid cysts typically present with long T1 and T2 signals on MR images. Other epidermoid cysts with atypical MR images are often misdiagnosed as other diseases. In this study the authors aimed to analyze the incidence and the clinical, radiological, and pathological features of atypical epidermoid cysts.

Methods

Among 428 cases of intracranial epidermoid cysts that were surgically treated between 2002 and 2008 at Beijing Tiantan Hospital, cases with an atypical MR imaging appearance were chosen for analysis. Clinical and pathological parameters were recorded and compared in patients with lesions demonstrating typical and atypical MR appearance.

Results

An atypical epidermoid cyst accounts for 5.6% of the whole series. Radiologically, 58.3% of atypical epidermoids were misdiagnosed as other diseases. Compared with a typical epidermoid cyst, atypical epidermoid lesions were significantly larger (p = 0.016, chi-square test). Pathologically, hemorrhage was found in 21 patients with atypical epidermoid cyst and is significantly correlated with granulation (p = 0.010, Fisher exact test). Old hemorrhage was found in 13 cases and was significantly correlated with cholesterol crystals. Twenty-one patients were followed up for 1.3–8.6 years after surgery. The 5- and 8-year survival rates were both 100%. Three patients experienced cyst recurrence. The 5- and 8-year recurrence-free rates were 95% and 81.4%, respectively.

Conclusions

Radiologically, an atypical epidermoid cyst should be differentiated from dermoid cyst, teratoma, schwannoma, glioma, craniopharyngioma, and cavernous angioma. A tendency toward spontaneous hemorrhage is confirmed in atypical epidermoid cysts, and a hypothesis was proposed for spontaneously intracystic hemorrhage in atypical epidermoid cysts. Follow-up confirmed long-term survival of patients with atypical epidermoid cysts.

Abbreviations used in this paper: CPA = cerebellopontine angle; KPS = Karnofsky Performance Scale.

Article Information

Address correspondence to: Song Lin, M.D., Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Tiantan Xili No 6, Beijing 100050, China. email: linsong2005@126.com.

Please include this information when citing this paper: published online December 16, 2011; DOI: 10.3171/2011.10.JNS111462.

© AANS, except where prohibited by US copyright law.

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Figures

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    Kaplan-Meier plots for atypical epidermoid cyst. The 5- and 8-year progression-free survival rates for patients with atypical epidermoid cyst were 95% and 81.4%, respectively. The 5- and 8-year overall survival rates for patients with atypical epidermoid cysts were both 100%.

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    Photomicrographs. A: Classic pathological features showing squamous epithelium and stratified keratin debris. B: Tissue section showing hemorrhage within granulation. C and D: Tissue samples showing cholesterol crystals with fresh hemorrhage and hemosiderin accumulation in granulation, respectively. E and F: Tissue samples showing destruction of blood vessels in granulation. H & E, original magnification × 400 (A and E), × 40 (B), × 100 (C and D), × 200 (F).

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    Case 2. The lesion in this patient was misdiagnosed as craniopharyngioma. The MR images reveal a lesion in the sella and left CPA with mixed T1 (A and D) and mixed T2 (B) signals, without enhancement on T1-weighted images obtained after addition of contrast material (C). Pathological examination reveals fresh hemorrhage, old hemorrhage, and cholesterol crystals within granulation (E–G). Original magnification × 200 (E), × 100 (F and G).

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    Case 7. The lesion in this patient was misdiagnosed as trigeminal schwannoma, and the long-term follow-up demonstrated slow growth of the tumor. A–D: The MR images reveal a parasellar lesion with mostly mixed T1 (A) and T2 (B) signals without enhancement after addition of contrast material in T1-weighted images (C and D). E and F: Photomicrographs of tissue samples obtained for pathological examination revealing fresh hemorrhage within granulation. G–K: Axial MR images obtained for long-term follow-up demonstrating slow growth of the tumor: 9 days after surgery (G); 3 months after surgery (H); 1 year after surgery (I); 2 years after surgery (J); and 5.5 years after surgery (K). H & E, original magnification × 200 (E and F).

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    Case 8. A–D: Axial and coronal MR images of a well-defined right parasellar mass showing mostly short T1 (A) and short T2 (B) signals, without enhancement (C and D). E–G: Photomicrographs of tissue samples obtained for pathological examination revealing the diagnosis of epidermoid cyst with fresh hemorrhage and hemosiderin deposition. H & E, original magnification × 200 (E), × 400 (F and G).

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    Case 14. The lesion in this patient was misdiagnosed as cavernous angioma. A–C: Axial CT scan (A) revealing a parietal lesion with calcification. Axial MR images revealing a lesion that was mostly isointense on a T1-weighted (B) and hyperintense on a T2-weighted (C) image. D–G: Photomicrographs of tissue samples obtained for pathological examination revealing fresh and old hemorrhage, as well as cholesterol crystals within granulation. H & E, original magnification × 200 (D), × 400 (E and F), × 100 (G).

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    Case 18. The lesion in this patient was misdiagnosed as glioma. A–C: Axial MR images revealing a poorly defined frontal lesion with mixed signal on a plain T1-weighted image (A) and long signal on a plain T2-weighted image (B), with slight enhancement on a T1-weighted image obtained after addition of contrast material (C). D and E: Photomicrographs of tissue samples obtained for pathological examination revealing the diagnosis of epidermoid cyst with fresh hemorrhage in granulation. H & E, original magnification × 200 (D and E).

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    Case 19. The lesion in this patient was misdiagnosed as teratoma. A–D: Preoperative MR images of a parasellar mass in the right cavernous sinus showing mixed T1 (A) and mixed T2 (B) signals with no enhancement (C and D). E–G: Photomicrographs of tissue samples obtained for postoperative pathological investigation, which revealed the diagnosis of epidermoid cyst with fresh hemorrhage, old hemorrhage, and cholesterol crystals in the granulation. H & E, original magnification × 200 (E–G).

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