Malignant transformation eight years after removal of a benign epidermoid cyst: a case report.
Malignant transformation of benign epidermoid cysts is rare and their prognosis remains poor. A 56-year-old woman presented with left facial hypoesthesia and photophobia in the left eye. She had undergone removal of a benign epidermoid cyst in the cerebellopontine angle 8 years previously. Magnetic resonance imaging of the brain revealed a cystic lesion in the left cerebellopontine angle. The cyst wall was enhanced by gadolinium-DTPA. She underwent removal again and the histopathologic diagnosis was squamous cell carcinoma. Gamma knife radiosurgery was performed on the remnant lesion with a marginal dose of 15 Gy. The tumor shrank rapidly for 2 months after radiosurgery, but recurred 9 months later. She underwent radiosurgery again with a marginal dose of 12 Gy. A gradual increase in the size of the enhanced lesion was seen during the 4-month follow-up period subsequent to the second radiosurgery. Careful observation, employing serial magnetic resonance images, is necessary for incompletely resected epidermoid cysts because intervals before malignant transformation reportedly range from 3 months to 33 years. Newly identified contrast enhancement strongly indicates malignant change in epidermoid cysts. Gamma knife radiosurgery may be useful for short-term control of intracranial squamous cell carcinomas, but long-term effects are presently unknown.
Tamura
Kaoru
K
Department of Neurosurgery, Graduate School, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan.
Aoyagi
Masaru
M
Wakimoto
Hiroaki
H
Tamaki
Masashi
M
Yamamoto
Kohei
K
Yamamoto
Masaaki
M
Ohno
Kikuo
K
D002294:Carcinoma, Squamous Cell / Q000473:pathology* / Q000601:surgery; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D002528:Cerebellar Neoplasms / Q000473:pathology* / Q000601:surgery; D002530:Cerebellopontine Angle / Q000473:pathology* / Q000601:surgery; D004814:Epidermal Cyst / Q000473:pathology* / Q000601:surgery; D005260:Female; D005682:Gadolinium; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000601:surgery; D016634:Radiosurgery
D005682:Gadolinium