Tumor-simulating Retrorectal Heterotopia of Bone Marrow

Abstract

A retrorectal tumor-simulating mass of extramedullar hematopoiesis was discovered during work-up for uterine bleeding in a 40-year-old woman. It was excised in toto. The only hematologic abnormality at the time was iron deficiency, which was corrected. Six years later the patient is free of recurrence or any hematologic abnormality. It is suggested that this case represents heterotopic marrow arising either as a remnant of embryonic hematopoiesis or from activated primitive cells retaining the embryonic potentiality of hematopoiesis. The difficult diagnostic problems, pathogenesis and treatment are discussed, and the importance of recognizing the trilineage of hematopoiesis using Wright’s-stained imprints of the mass is emphasized.