ABSTRACT
Introduction: Our knowledge of genetic contributions to malignancy risk has increased greatly over the past two decades. It is now known that BRCA1 gene mutation is associated with a 50% lifetime risk of developing malignancy.Women who carry a BRCA1 mutation have a 47-66% lifetime risk of developing breast cancer, a 63% chance of developing cancer in the contralateral breast at 25 years, and a 35-46% lifetime risk of developing ovarian cancer.1,2 BRCA1 mutation carriers also have increased rates of pancreatic cancer (odds ratio [OR], 2.26), leukemia, and lymphomas (OR, 2.6).3,4 There is conflicting evidence regarding the effect of BRCA1 mutation on a patient's risk of developing colorectal cancer, but it may increase the risk up to 1.5 times.5,6 Independent of known genetic syndromes, cancer survivors are 14% more likely to be diagnosed with a new malignancy than those who have not had a previous cancer.1 Patients with colorectal cancer at stage two or three have a 40% recurrence rate after primary therapy, with more than 90% of recurrences occurring within the first 5 years.7 Transformation of follicular lymphoma to diffuse large B-cell lymphoma (DLBCL) occurs in up to 24% of cases, although it is less common in patients who have achieved clinical remission. Overall, this improved knowledge has resulted in increased surveillance for recurrence and associated malignancies. Case report: A 77-year-old woman underwent colonoscopy after lymphoma surveillance screening incidentally revealed a positron emission tomography-avid cecal lesion. This was on a background of previous colorectal cancer, managed with a left hemicolectomy and adjuvant chemotherapy with 5-fluorouracil and leucovorin in 1995. The patient was overdue for colonoscopy surveillance due to delays attributed to the COVID-19 pandemic. She was asymptomatic, with no weight loss, fevers, or night sweats. She denied change in bowel habit, with daily motions without the presence of tenesmus, melena, or rectal bleeding. Her past medical history was also significant for known BRCA1 positivity, which was diagnosed following bilateral breast cancer, affecting the right breast in 1981 and left breast in 1991. This was treated with bilateral mastectomy and axillary dissection. The patient received prophylactic hysterectomy and bilateral salpingo-oophorectomy in 2000. She previously had stage IIIa low-grade follicular lymphoma and received six cycles of bendamustine plus rituximab in 2018 and was considered in remission, with ongoing 6-monthly surveillance imaging. The patient's other medical conditions included metabolic syndrome, gastroesophageal reflux disease, osteoporosis, depression, left lacunar infarct, epilepsy, and cataracts. Examination revealed a non-tender abdomen with central adiposity. There was no palpable abdominal mass or evidence of hepatosplenomegaly or lymphadenopathy. She had a normal cardiovascular and respiratory examination. Colonoscopy showed a large two-thirds circumferential non-obstructing mass in the cecum. There was no evidence of bleeding, and the mass was biopsied. Histology showed that atypical lymphoid cells were present at an ulcer base with surrounding necrotic tumor cells. These cells were strongly positive for BCL2, CD45, CD20, and CD79a within the nodular lymphoid aggregate and negative for AE1/3 and CAM5.2. This appearance was consistent with a diagnosis of high-grade DLBCL. The patient had her care transferred to her hematologist, who confirmed a diagnosis of DLBCL and instigated six cycles of modified R-CHOP regimen for chemotherapy. Conclusion(s): This is a rare case of colorectal lymphoma and illustrates the well-documented risk of progression from follicular lymphoma to the more sinister DLBCL. It highlights the complexity of cancer genetics, justifies the increased need for malignancy surveillance within these groups, and confirms the importance of biopsy for all abnormal colorectal lesions.