Leiomyosarcoma of the gastro-intestinal tract: general pattern of metastasis and recurrence.

Clinically, epithelial cancers (squamous cell carcinoma and adenocarcinomas) metastasize primarily by the lymphatic route, while mesenchymal sarcomas more frequently enter the blood stream directly. Nevertheless metastatic involvement of regional nodes has been seen in 13% of patients with soft tissue sarcomas and in 7% of bone sarcomas at initial presentation (29). About one-third of the leiomyosarcomas of the gastro-intestinal tract developed metastasis and about 90% of the metastasis were intra-abdominal (45). Liver is the most common site of metastasis, followed by peritoneal seeding and local recurrence or extension. Regional nodal metastasis also has been noted both initially and subsequently. The most important criterion of diagnosing leiomyosarcoma appears to be the presence of mitosis. Leiomyosarcoma with 1 mitosis per 2 high power fields or epithelioid leiomyosarcoma with 1 mitosis per 5 fields behaved aggressively. Additional criteria useful for diagnosing and for determining prognosis of malignancy include the presence of necrosis, cellular atypia, and the gross size of the tumor. In general, almost all tumors larger than 5 cm in diameter should be viewed with suspicion. For patients with gastric leiomyosarcomas, a proportion, sometimes as high as 14%, had perigastric lymph node involvement at diagnosis (9), and about 7% of those who relapsed had regional nodal metastasis (Table 2). For patients with leiomyosarcoma of the small intestine, about 5% of the patients had nodal metastasis initially, and 9% subsequently (Table 4). Regional lymphatic metastasis also has been reported in leiomyosarcoma of the colorectum. It is believed that wide resection of normal tissues (at least 10 cm margin on either side of tumor) and adjacent mesentery (with routine omentectomy for gastric lesions) not only may discover a higher frequency of occult metastasis in the regional lymph node, but will also decrease the chance of loco-regional relapse and the occurrence of sarcomatosis. As a result of this review and a previous one (30), the surgeon ought to consider when faced with a smooth muscle tumor of the gastro-intestinal tract a wide segmental resection including the adjacent mesentery and omentum, because (a) the precise histologic nature of the lesion (benign vs. malignant) is hard to define even by permanent sections; (b) the possibility of involvement of draining nodes exists and (c) little or no increase in morbidity is anticipated between a wide, as against a limited wedge or segmental resection of gastrointestinal tract. The last point does not need elaboration, except for the very unusual lesions of the duodenum, distal stomach or lower rectum. When adherence to this principle would require a pancreaticoduodenectomy, near total gastrectomy or abdominoperineal resection, it may be wise to establish a definitive histologic diagnosis of the primary lesion first, and to use a more conservative procedure initially.