Myeloid sarcoma of the colon as initial presentation in acute promyelocytic leukemia: A case report and review of the literature

BACKGROUND: Myeloid sarcoma (MS) rarely occurs in acute promyelocytic leukemia (APL) at onset, but it can develop in relapse cases, especially after APL treated with all-trans retinoic acid (ATRA). Therefore little is known about the clinical features and suitable treatment for APL related MS due to the rarity of the disease, although this may be different from the treatment and prognosis of MS in the relapse stage. To our best knowledge, this is the second case report of APL initial presentation as colon MS. CASE SUMMARY: A 77-year-old woman complained of intermittent right lower abdominal pain, black stool, and difficult defecation for 2 mo. Physical examination showed diffuse tenderness during deep palpation and an anemic appearance. Laboratory findings showed positivity for fecal occult blood testing; white blood cell count: 3.84 × 10(9)/L; hemoglobin: 105 g/L; platelet count: 174 × 10(9)/L; and negativity for tumor markers. Abdominal enhanced computed tomography showed a space occupying lesion in the colon (1.9 cm). Fibrocolonoscopy revealed a polypoid and ulcerated mass measuring 2.5 cm. The tumor was removed. To our surprise, MS was confirmed by immunohistochemistry. PML/RARα fusion gene was detected in colon specimens by fluorescent in situ hybridization and real-time reverse transcription polymerase chain reaction, which was consistent with the bone marrow. She was diagnosed as having APL related MS. A smooth and unobstructed intestinal wall was found by fibrocolonoscopy, and continuous molecular remission was confirmed in both the bone marrow and colon after four courses of ATRA + arsenic trioxide (ATO). ATRA + ATO showed a favorable therapeutic response for both APL and MS. CONCLUSION: Early use of ATRA can benefit APL patients, regardless of whether MS is the first or recurrent manifestation.