Heterotopic Ossification of the Mesentery: A Rare Postoperative Complication

Heterotopic ossification is a rare, reactive condition, sometimes classified as a "pseudotumor,"involving the formation of bone within the soft tissues (Int J Surg Case Rep 2014;5:476-479), This process can occur as an undesirable pathologic sequela of trauma and surgery (JAm Acad Orthop Surg 2004;12:116-125). The few cases reported in the literature are almost exclusively in men with a predominance in people of African ancestry (J Am Acad Orthop Surg 2004;12:116-125; Bone Joint J 2016;98-B:761-766; Case Rep Surg 2019;2019:4036716). Reports of heterotopic ossification have been described in medical literature since 1692 as myositis ossificans progressiva (JBJS 1938;20:661-674). It was not until 1999 that the term "heterotopic mesenteric ossification"was formally used by Wilson et al to describe a complication found in post- abdominal surgical patients (Am J Surg Pathol 1999;23:1464-1470). Although the exact pathologic mechanismof heterotopic mesenteric ossification has not been elucidated, some hypotheses include differentiation of mesenchymal progenitor cells toward an osteogenic lineage, as well as proliferation of dislocated fragments of bone from other regions of the body (J Gastrointest Surg 2015;19:579-580). Since the late 1900s, fewer than 40 cases of mesenteric ossification have been reported. Limited gross and histologic description is available for pathologists and surgeons to identify this phenomenon; however, further data can be acquired at autopsy. Awareness of this condition on the part of clinicians, and early review and recognition by pathologists, may alter surgical management decisions and improve upon morbidity and mortality in these patients.We present gross and histologic examination of an advanced case of heterotopic ossification at autopsy, with a review of current management recommendations.