Primary lymphoma of gastrointestinal tract most commonly
involves the stomach then followed by the small
intestine and colorectum. They are generally B-cell phenotype.
Primary T/natural killer (NK) cell lymphoma of
the colon is extremely rare. The classification of T-cell and
NK-cell neoplasms proposed by the WHO classification
emphasises a multiparameter approach, integrating morphologic,
immunophenotypic, genetic, and clinical features.
Clinical features play particular importance in the
subclassification of these tumors, in part due to the lack of
specificity of other parameters. Mature T-cell (post-thymic)
and NK cells share similar immunophenotype and
functional properties. Because of that reason neoplasms
of these cells are classified under the same subtype in the
WHO histological classification.
Extranodal NK/T-cell lymphoma (ENTCL), nasal
type, is a predominantly extranodal lymphoma characterized
by a broad morphological spectrum, infiltrate is
often angiocentric, with prominent necrosis and vascular
destruction. It is designated NK/T-cell lymphoma because
while most cases appear to be NK-cell neoplasm (EBV+
CD56+), rare cases show an EBV+ CD56- cytotoxic T-cell
phenotype. Enteropathy-type T-cell lymphoma (ETCL) is
a tumor of intraepithelial T-lymphocytes, showing varying
degrees of transformation but usually presenting as a
tumor composed of large lymphoid cells. This tumor occurs
most commonly in the jejunum or ileum and is usually
associated with coeliac disease.
Both ENTCL, nasal type and ETCL in GI tract form
ulcerating mucosal masses that invade the wall of the
intestine. These cases can cause diagnostic challenge to
physicians and pathologists. Early symptoms and colonoscopic
findings may be similar to those of inflammatory
bowel disease. Neoplastic cells show variable cytological
appearances, including a prominent mixture of inflammatory
cells, such as normal appearing small lymphoid cells,
plasma cells, and less often eosinophils and histiocytes.
Therefore, it may be difficult to distinguish the disease
from an inflammatory or infectious process as in our
case.
The morphologic and immunophenotyping studies
show a peripheral T cell lymphoma most consistent with
either ETNCL, nasal type or ETCL. Due to the lack of
clinical information the case could not be further classified.
A history of coeliac disease would support ETCL.
Although the case is negative for CD56, rare cases of
CD56 negative (CD3+ CD56+/-) ENTCL, nasal type
have been published in the literature. Focal EBER (by in
situ hybridization) positivity and colonic localization favor
ENTCL, nasal type. Several authors have suggested
that CD56 expression on tumor cells plays an important
role in early dissemination. The disease often has a rapid
progressive course and poor prognosis.
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