Myeloid sarcoma and adenocarcinoma of the large bowel as collision tumors: a case report.

Myeloid sarcoma is a rare tumor composed of myeloid cells, localized in an extramedullary site, which may be associated with a concurrent myeloid neoplasm involving the bone marrow, although such an association is not required. Most patients present with acute myeloid leukemia and their prognosis is poor. We describe the case of a 76-year old woman with an adenocarcinoma of the right colon infiltrating the subserosa synchronous with a myeloid sarcoma at the same site; one pericolic lymph node was infiltrated by both tumors. The peculiarities of this case are the clinical presentation (as an acute abdomen due to subserosa infiltration by the myeloid sarcoma), the coexistence of a myeloid sarcoma with an adenocarcinoma of the right colon, and the absence of progression to acute leukemia. Coexistence of myeloid sarcoma and adenocarcinoma in the colon is probably incidental, and so it appears likely that the two different tumours arose from different mechanisms. However, a possible common background is conceivable. Some authors have found that p53 has a pivotal role in driving the maturation of myeloid stem cells and p53 is, also, involved in colon carcinogenesis. In our case, it may be hypothesized that synchronous heterogeneous mutations occurred in different types of committed cells or in stem cells secondary to p53 loss. Since only one case report has evaluated the correlation between myeloid sarcoma and adenocarcinoma of the large bowel, further immunohistochemical and molecular studies are needed to clarify the pathogenetic relationship between them.