[TUMORS of the stomach].

This collective review includes all available case reports of smooth muscle (stromal) tumors of the stomach in the world literature from 1762 to 1996. It updates our previous review from 1767 to 1959. Overall, we identified 2189 patients with leiomyoma (LM) and 1594 with leiomyosarcoma (LMS). The peak age of incidence of LM was 50 to 59 years, while LMS was most frequently seen between ages 60 and 69. Women were more likely to develop LM, and men more commonly presented with malignant smooth muscle tumors of the stomach. Concerning the patterns of growth, LMs were more likely to grow intraluminally (endogastric), whereas LMSs were predominantly exogastric. The most common site of LMs was on the anterior or posterior wall of the body of the stomach; LMSs were most likely found along the greater curve. The presenting symptoms of both types of smooth muscle tumors were similar; in decreasing order of frequency they were bleeding, pain, palpable mass, and weight loss. Interestingly, there was no correlation between the size of the tumor and signs or symptoms of bleeding, pain, weight loss, or ulceration, although patients with LMSs were more likely to report weight loss than patients with benign tumors. For LMS, there seemed to be no correlation between tumor size or location and rate of metastasis, although the tumors that grew in a dumbbell shape (i.e., both intraluminally and extraluminally) had a higher frequency of metastasis than other growth patterns. Overall, the rate of metastasis at diagnosis was 35.4%, with the liver, spleen, and regional lymph nodes the most common sites. Carcinoma is responsible for 92% to 99% of all malignant gastric neoplasms. Of the noncarcinomatous malignancies, lymphomas are the most frequent as reported by Marshall and Meissner [1]. The remaining are predominantly LMSs with an incidence as high as 25% of all noncarcinomatous malignancies. Other rare sarcomas include rhabdomyosarcoma, neurofibrosarcoma, fibroliposarcoma, fibrosarcoma, and hemangiosarcoma. Pathologists have begun to shift from the terms leiomyoma and leiomyosarcoma to the term stromal cell tumor. They might additionally use the smooth muscle terminology of leiomyoma or leiomyosarcoma if there is clear evidence for this differentiation [2]. Almost all the cases in this review were reported prior to widespread recognition that many of the tumors formerly called smooth muscle tumors lack the immunohistochemical or ultrastructural features characteristic of smooth muscle. Nevertheless, as yet there is no indication that the presence or absence of true smooth muscle features has any prognostic importance. Thus we believe the collective data of tumors classified as LM or LMS reported here have clinical importance. Smooth muscle tumors of the stomach originate from the smooth musculature of the gastric wall and proliferate toward the lumen, toward the serosa, or in both directions; or they remain small and within the gastric wall itself. Both benign and malignant tumors may be sessile or pedunculated and show huge diversity in size, presentation, and duration of symptoms. LMs have a firm, rubbery consistency and on occasion are calcified. LMs are the most common benign tumor of the stomach and the most common gastric tumor to show calcification. LMs are often encapsulated or pseudocapsulated; and they range in color from brown to tan to reddish pink. Cystic degeneration with ulceration, cavitation, and hemorrhage is not a common observation of benign smooth muscle tumors. In contrast, LMSs are more often soft, irregularly shaped, semisolid masses with cystic necrotic areas, often with ulcerated luminal surfaces. These malignant neoplasms are less frequently encapsulated and can be yellow, gray, or reddish brown [3]. Despite increasing knowledge about smooth muscle (stromal) tumors, their exact etiology is still unknown. Research concerning uterine LMs has produced an impressive amount of data implicating a clonal origin of these tumors, which is perhaps true for smooth muscle tumors in other locations. LMs and LMSs have their origin in the smooth muscle of the stomach wall, including the muscularis mucosae, isolated smooth muscle fibers in the subserosa and submucosa, and possibly in the muscular walls of the stomach’s vasculature. Although it had originally been thought that LMSs may arise from previously benign LMs, autopsy reports by Meissner [4] and others [5–8] have suggested that it is unlikely. Clonal chromosomal aberrations have been found in many uterine LMs; translocations of chromosomes 12 and 14 have existed in 20% of the uterine LMs studied. These translocations result in an altered DNA binding protein, leading to subsequent alteration of transcription regulation. A more complex set of cytogenetic malformations, as yet unidentified, may be responsible for the malignant LMS. Skandalakis and colleagues initially reported in 1960 that 40% of all benign gastric tumors were LMs and that 25% of all gastric Supplementary material for this article is available for subscribers at http://link.springer-ny.com/ Correspondence to: J.E. Skandalakis, M.D., Ph.D. sarcomas were LMSs [9]. The figures are still considered valid today. LMs are considerably more common than the malignant LMSs. According to Pack [10], autopsy reports have demonstrated the presence of miniature, insignificant, often asymptomatic LMs in as many as 25% to 40% of all stomachs examined by pathologists. Marshall [11] stated that the incidence of gastric smooth muscle tumors was approximately 2.47% of all gastric tumors. This number was based on finding 28 LMs and 16 LMSs during 1700 gastric tumor operations that took place at the Lahey Clinic. Schindler et al. [12] reported the gastric carcinoma/sarcoma ratio to be about 100:1 and that LMSs comprised 1% to 3% of all gastric malignancies. Due to the rarity of gastric sarcomas in general, only a few accounts of significantly high numbers of these tumors are found in the recent literature [6, 7, 13–15], making an accurate prediction of the incidence more difficult. Materials and Methods This paper on smooth muscle tumors of the stomach is part of a series of publications addressing the issue of smooth muscle tumors of the gastrointestinal (GI) tract. Chaffin had collected 280 cases of LM and 83 cases of LMS from the world literature in 1938 [16]. Skandalakis and Gray [17], in a collective review through 1959, added 535 LMs and 260 LMSs. The goal of this collective review is to update the previous data with all available reports of LM and LMS of the stomach published in the world’s medical literature from 1960 to 1996. The present review adds 1374 LMs and 1251 LMSs of the stomach. Of the 1374 LMs reported since 1960, there were 1161 in series and 213 in case reports; 188 of the LMSs were reported in case reports and 1063 reported in series (see Additional Cases Collected, supplementary material available only to subscribers at http://link.springer-ny.com). Overall, 2189 LMs were reported in the world literature from the first case in 1762 until 1996, with 1594 LMSs reported during this same time span. Literature searches were performed using MEDLINE databases from 1960 to 1996 with the key words: leiomyoma/leiomyosarcoma/smooth muscle tumor/stromal tumor, and stomach/gastric. Statistical differences were identified by chi-square frequency analysis for data with large sample sizes and Fisher’s exact test, where indicated, for data with small sample sizes. Significance was defined as p , 0.05.