B-lymphoblastic lymphoma of the rectum

Abstract

Lymphoblastic lymphoma is a neoplasm of immature cells committed to the B-cell or T-cell lineage. B-lymphoblastic lymphoma usually involves lymph nodes and extranodal sites, such as the skin, bone, and soft tissue. The rectum is a very rare site of involvement in B-lymphoblastic lymphoma. We describe a 26-year-old man who presented with bleeding per rectum and fecal incontinence. Endoscopy showed a large nodular friable lesion narrowing the entire rectal lumen. Biopsy was diagnostic of B-lymphoblastic lymphoma. He was started on chemotherapy with the Berlin-Frankfurt-Münster protocol and achieved complete remission after induction chemotherapy. This is the first report of B-lymphoblastic lymphoma presenting as a rectal lesion in the world literature.

Lymphoblastic lymphomas/leukemias are neoplasms of precursor T cells and B cells. Lymphoblastic lymphoma (LBL) is a disease predominantly involving lymph nodes with less than 20% involvement in the bone marrow, while lymphoblastic leukemia is predominantly a bone marrow and circulating blood disease with little nodal involvement. LBL may be either T or B cell in origin. B-lymphoblastic lymphoma (B-LBL) comprises only 10% to 15% of LBLs. It usually involves lymph nodes and extranodal sites, such as the skin, bone, and soft tissue (1). The rectum is a very rare site of involvement of B-LBL. We report a case of B-LBL involving the rectum in a 26-year-old man. The present case, to the best of our knowledge, is the first reported case of B-LBL involving the rectum.

CASE PRESENTATION

A 26-year-old man presented with constipation, bleeding per rectum, and significant loss of weight of 10-month duration along with recent-onset perianal pain and fecal incontinence. His Eastern Cooperative Oncology Group performance status was 0. Rectal examination revealed a proliferative growth starting 1 cm above the anal verge and ascending upwards and involving the entire circumference with resultant obstruction of the lumen of the rectum. Anal sphincter tone was lost. Computed tomography scan of the abdomen and pelvis revealed an asymmetric circumferential wall thickening involving the entire length of the rectum extending from the rectosigmoid junction superiorly to the anal canal inferiorly, of size 15 × 5 cm, with marked narrowing of the rectal lumen along with a few enlarged lymph nodes at the perirectal and iliac levels (Figure 1). A large nodular friable lesion narrowing the entire rectal lumen was visualized by flexible sigmoidoscopy and a biopsy was taken. Histopathological examination showed collections of medium-sized lymphoid cells with scant cytoplasm and round nuclei (Figure 2). On immunohistochemistry, the cells were positive for Tdt, CD10, PAX 5, and CD43 with MIB labeling index of 90%. The picture was diagnostic of B-LBL involving the rectum.

Figure 1.

CT of the abdomen showing asymmetric circumferential wall thickening involving the entire length of the rectum.

Figure 2.

Rectal biopsy showing infiltration by a monotonous population of small lymphoid cells with immature chromatin (hematoxylin and eosin, ×400).

His hematology, serum chemistries, cerebrospinal fluid, and bone marrow studies were normal. He did not have disease elsewhere. He was staged as Ann Arbor 1 AE. He was given combination chemotherapy with the Berlin-Frankfurt-Münster 95 protocol. He achieved complete remission after induction chemotherapy and is presently receiving consolidation chemotherapy.

DISCUSSION

LBL is a highly aggressive neoplasm of lymphoblasts committed to the B- or T-cell lineage. In the 2008 World Health Organization classification of hematopoietic malignancies, LBL is grouped together with acute lymphoblastic leukemia (2), but these two entities are not identical. In LBL, the bone marrow shows <20% infiltrating blast cells. Unlike acute lymphoblastic leukemia, T-LBL is far more common than B-LBL. LBL accounts for approximately 2% of all non-Hodgkin lymphomas (1).

Common sites of involvement of B-LBL are lymph nodes and extranodal sites, especially bone, skin, and soft tissue. The incidence of skin involvement is much higher in B-LBL (33%) than acute lymphoblastic leukemia (1%) (3). Mediastinal masses, which are a characteristic finding in T-LBL, are much less frequent in B-LBL. In their study of 25 patients with B-LBL, Lin et al found that the most common initial symptom was localized or migratory pain. The presenting sites of primary disease included the skin, bones, soft tissue, lymph nodes, breast, stomach and colon, and mediastinum in decreasing order of frequency. None of the patients had rectal involvement (4).

Histopathological examination of the involved organ shows a diffuse proliferation of lymphoblasts similar to acute lymphoblastic leukemia cells. The differential diagnosis includes other hematologic malignancies of B-cell origin, such as the blastic subtype of mantle cell lymphoma, large cell lymphoma, Burkitt lymphoma, and others like the Ewing family of tumors and myeloid leukemias. Immunohistochemical characteristics are used to differentiate between these entities. B-cell markers CD19, CD79a, and CD22 are always positive in B-LBL. Most cases also express CD10, CD24, PAX5, and terminal deoxytransferase. Pathogenetic factors and risk factors for LBL are mostly unknown (5). The pathophysiology of extramedullary involvement in LBL is not fully understood (6). The typical cytogenetic aberrations seen in medullary acute lymphoblastic leukemia are less frequent in LBL.

Staging procedures include bone marrow evaluation, cerebrospinal fluid cytology, computed tomography scan of chest and abdomen, and 18F-fluorodeoxyglucose positron emission tomography. In adult LBL, the unfavorable prognostic factors are older age (>40 years) and advanced stage (7, 8). Chemotherapy is the cornerstone of treatment for LBL. Standard lymphoma-like therapy is less effective in LBL, and hence protocols for acute lymphoblastic leukemia are recommended for LBL, which include an intensive remission induction chemotherapy, an early central nervous system prophylaxis, consolidation blocks, and subsequent maintenance therapy. In colorectal lymphoma, surgical treatment is now generally reserved for clinical indications such as bowel obstruction or bleeding in an emergency setting (9). Since lymphoblastic lymphoma of the rectum is very rare, it is essential for physicians to be aware of this aggressive but extremely chemosensitive disease to avoid unnecessary surgical procedures.