Primary appendiceal precursor B lymphoblastic lymphoma with peculiar morphology mimicking diffuse large B cell lymphoma.

Precursor B lymphoblastic neoplasm usually presented as childhood leukemia. Most precursor lymphoblastic lymphoma are T-cell lineage and precursor B lymphoblastic lymphoma constitutes only about 10% of cases according to the WHO Classification of Tumours of Haematologic and Lymphoid Tissues. The most frequent sites of involvement in precursor B lymphoblastic lymphoma are the skin, soft tissue, bone and lymph nodes. Primary appendiceal involvement is an uncommon condition. We present an unusual case of primary appendiceal precursor B lymphoblastic lymphoma in an 11-year-old boy with peculiar histological morphology mimicking diffuse large B cell lymphoma. Histologically, the tumor was composed of diffusely infiltrated large cells from mucosa and extended to the subserosal area. The tumor cells were positive to CD79a, CD20, PAX5, BCL2, CD10, TdT, p53 but not to CD3, BCL6 and CD34 by immunohistochemical studies. The response to conventional treatment regimen for lymphoblastic lymphoma was not good, with early relapse within three months. Partial remission was achieved by adding rituximab. Unfortunately, the patient died in ten months due to uncontrolled relapsed disease with generalized lymphadenopathy and massive pleural effusion. The special morphologic changes and poor response to chemotherapy may be related to the overexpression of p53.