Leiomyoblastoma: Behavior and prognosis

Four cases of leiomyoblastoma are presented which illustrate the clinical presentations and gross anatomical appearance associated with this type of tumor when it is clinically significant. Case 1 is unique in having a markedly elevated mitotic rate with no evidence of metastasis at autopsy; it is the third case presenting as a pancreatic pseudocyst. Twenty‐two cases of leiomyoblastoma reported in the literature since 1962 are reviewed. Experience with varying clinical presentations, gross anatomical and histologic appearances, and results of surgical therapy are summarized. Seven examples of metastasis of this tumor have been reported. In each case the rate of mitosis had significantly increased. Case 1 of our series had a mitotic rate from 2 to 3 times higher than those that metastasized, but no evidence of metastasis was present at autopsy. There may be variants of leiomyoblastomas with elevated mitotic rates that do not metastasize or do so only after a protracted course. Nevertheless, the mitotic rate remains die best criterion for prognosis.