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Figure 2. Rectal biopsy showing infiltration by a monotonous population of small
lymphoid cells with immature chromatin (hematoxylin and eosin, ×400).

for Tdt, CD10, PAX 5, and CD43 with MIB labeling index of
90%. The picture was diagnostic of B-LBL involving the rectum.
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-FrankfurtMünster 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 BLBL, 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,
July 2017

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.
1.

5.
6.

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