Natural Killer Cell Lymphoma at an Unusual Location

Abstract

Purpose: Introduction: Primary intestinal natural killer (NK)-cell lymphomas are exceedingly rare. We present a case of NK- cell lymphoma in the stomach and colon Case Report: 45 year old female with history of peptic ulcer perforation who was undergoing surveillance upper endoscopies every two years showed erosive gastritis (Fig. 1A). The gastric biopsy showed active ulceration of fundic gastric mucosa with glandular atypia and abundant lymphocytes which were positive for CD3, CD56, and CD43 by immunohistochemistry. PET scan demonstrated high radioactivity on the left side of the pelvis. A subsequent colonoscopy revealed numerous moderate sized exudative ulcers located throughout the colon (Fig. 1B). The colon biopsy was also positive for NK/T cell lymphoma. The tumor responded well to 6 cycles of CHOP regimen and subsequent EGD and colonoscopy with biopsys were negative for lymphoma which indicates the disease to be in complete remission Discussion: Primary NK cell lymphoma also known as angiocentric lymphomas or CD56 lymphomas have marked propensity to occur in the nose and paranasal sinuses. They are more common in men. This lymphoma produces usually ulcerative, destructive lesion in the nasal/nasopharyngeal region. Other organs include the skin, gastrointestinal tract, testis, soft tissue, brain, liver, spleen, and bone marrow. The identifying trait is found by immunohistochemistry which shows strong immunopositivity for CD56, a marker for natural killer (NK) cell differentiation. EBER and TCR gene rearrangement are useful in distinguishing NK cell lymphoma from NK-like T-cell lymphoma. The disease is closely associated with Epstein-Barr virus (EBV) infection. Natural killer cells comprise 10–15% of the normal circulating lymphocytes in the peripheral blood and play an important role in the immune system by lysing tumor cells without prior sensitization. In our patient as CD 30 was negative, this was not the usual aggressive NK/T cell lymphoma of nasal type. Treatment of NK/T-cell lymphomas is by standard CHOP regimen. Other treatment options, like peripheral blood stem cell transplant combined with chemotherapy for more resistant lymphomas do exist.Figure