SMOOTH muscle tumors of the stomach have a common occurrence in adults. The overwhelming majority of these tumors are benign leiomyomas, which are usually intramural, rarely grow to great size, occasionally produce symptoms, and very infrequently produce mucosal ulceration with resultant hemorrhage.1-2 Microscopically, these tumors show the typical intertwining bundles of smooth muscle fibers interspersed with lines of nuclei and greater or lesser amounts of fibrous connective tissue. These tumors are most often discovered as an autopsy finding or as an incidental finding during abdominal surgery.
Infrequently, the smooth muscle tumors present a more bizarre histologic pattern with nuclear palisades and with the majority of cells rounded or polygonal rather than the usual elongated shape of the differentiated leiomyoblast. The cells usually have no trace of smooth muscle fibers. However, mitoses are rare. Stout3 in 1962 published a discussion of this form of leiomyoma and described 69 cases.
Wolf JS. Massive Leiomyoblastoma of the Stomach. Arch Surg. 1968;96(2):284–288. doi:10.1001/archsurg.1968.01330200122026