Primary Ki-1-positive T-cell lymphoma of the brain--an aggressive subtype of lymphoma: case report and review of the literature.

BACKGROUND: By detection of the Ki-1 antigen, Stein (1985) defined a new entity of anaplastic large cell lymphoma [24]. Apart from our case, only four further cases of Ki-1 positive primary central nervous system lymphoma (PCNSL) have been reported in the literature to date. CASE REPORT: A 63-year-old man presented with two frontal and parietal mass lesions and one ring lesion on computed tomography scan. Clinically, no evidence of brain metastases or abscesses could be found. Immunohistochemical investigations of biopsy specimens revealed a large cell anaplastic T-cell lymphoma positive to Ki-1 antigen. In spite of all therapeutic efforts, the patient died less than 3 months after the onset of symptoms. DISCUSSION: In all cases the clinical course was very rapid, suggesting that Ki-1 positive PCNSL might form an aggressive subtype of lymphomas. Since the radiologic appearance was atypical and clinical diagnosis was not possible, diagnostic biopsy for immunohistochemical diagnosis should be performed.