extranodal B lymphoblastic lymphoma

Precursor B-cell lymphoblastic lymphoma (B-LBL) is uncommon and accounts for less than 10% of cases of lymphoblastic lymphoma.

The median age is 20 years (range, 5-68 yrs). 88% patients are younger than 35 years of age.

The primary sites of disease are :
 skin
 bones
 soft tissue
 lymph nodes
 breast
 stomach
 colon
 mediastinum

Histologically, each neoplasm was diffuse and composed of small to medium-sized lymphoid cells with blastic nuclear chromatin and a high mitotic rate.

All cases are positive for B-cell antigens and terminal deoxynucleotidyl transferase.

76.4% are positive for CD10.
54.1% are positive for CD20.

Unlike precursor T-cell lymphoblastic lymphoma, which commonly involves lymph nodes and the mediastinum, B-LBL usually involves extranodal sites, most often the skin, and rarely presents as a mediastinal mass.

With aggressive chemotherapy, patients with precursor B-LBL rarely develop leukemia and appear to have a better prognosis than do patients with B-ALL.

References

 Precursor B-cell lymphoblastic lymphoma: a predominantly extranodal tumor with low propensity for leukemic involvement. Lin P, Jones D, Dorfman DM, Medeiros LJ.
Am J Surg Pathol. 2000 Nov;24(11):1480-90. PMID: 11075849