Precursor B-cell lymphoblastic lymphoma (PBLL) in children: pattern of presentation and outcome

Precursor B-cell lymphoblastic lymphoma (PBLL) is a rare subtype of NHL seen primarily in children or young adults. There are approximately 100 immunophenotyped cases of PBLL; reported in the literature; most as single case reports or very small series. In this report, we describe patterns of presentation, and results of a retrospective study looking at patients with PBLL treated at KFSH and RC between 1993 and 2000.

We present results of a retrospective study looking at patients with PBLL treated at KFSHRC between 1993 and 2000, younger than 14 years of age (cut-off age for pediatric department). Six cases of PBLL were lacking evidence of blood and bone marrow involvement. Histologic sections were available for review in all cases.

Twenty one patients were treated for lymphoblastic lymphoma, of which six had a precursor Bcell phenotype. There were three boys and the median age at diagnosis was 6 years (range 3-13). In four of the patients the primary involved were oro-nasopharynx or the paranasal sinuses. One patient had a soft tissue mass in the upper thigh while one patient had a solitary bone lesion in the distal tibia. Four of the patients had limited stage disease (2 stage I and stage II), while 2 were stage IV. Both patients with stage IV disease had CNS involvement with blasts in the CSF. Both had paranasal primaries and had bone infiltration involving the base of the skull, with radiological documentation of intracranial extension in one patient. Median LDH level was 542 IU/L (range 463-5000). Five patients were treated according to B-cell NHL type protocols. Because of the specific diagnosis of PBLL, two of these patients were switched to an ALL-type protocol following post induction intensification; one died in remission due to encephalitis, while the other remained in CR almost 2 years after diagnosis. A third patient suffered a loco-regional relapse 17 months after completing first line therapy, and was re-treated on an ALL-type protocol, and currently is in remission 25 months following relapse. The fourth patient, who received 9 months of post induction therapy, remains free of disease 7 years following diagnosis. The fifth patient had local and CNS progression on therapy, and died of his disease. The last patient with a solitary bone lesion was misdiagnosed as Ewings' Sarcoma and received treatment for that disease. He suffered an isolated CNS relapse, and is in CR 12 months following the relapse, on an ALL treatment protocol.

PBLL is a distinct B-cell NHL which involves extralymphatic sites, with particular predisposition for the upper aerodigestive tract. Patients should not be treated on short intensive protocols used for other B-cell NHL but should receive treatment based on ALL protocols like those for treating T-cell LL.