Adjacent epidermoid cyst and primary central nervous system lymphoma: case report

BACKGROUND: Except for cases with radiotherapy or phacomatosis, multiple primary brain tumors of different histologic types are rare. The authors report the association of an epidermoid cyst and a primary CNS lymphoma. CASE DESCRIPTION: A 66-year-old man with a 20-year history of gait disturbance was admitted because of recently worsening symptoms. Magnetic resonance imaging showed an abnormal mass in the posterior fossa. The mass lesion had the appearance of a cystic tumor with a large mural nodule. Gross total removal of the tumor was performed. Histologic examination disclosed the cystic portion to be an epidermoid, whereas the nodular portion exhibited the histologic and immunohistochemical features of a malignant lymphoma. The lymphoma cells were shown to harbor EBV by in situ hybridization. CONCLUSIONS: To our knowledge, this is the first report of the coexistence of an epidermoid cyst and primary CNS lymphoma. When the lesions are adjacent, a definite preoperative diagnosis can be difficult. Epstein-Barr virus-associated CNS lymphoma is rare among the immunologically normal population. The possible pathogenesis for the coexistence of these 2 tumors is discussed.