Submucosal Tumors

11	Submucosal Tumors T. Eberl

Definition and Classification

As the term indicates, submucosal tumors are characterized by growth exclusively in the submucosa. Submucosal tumors occur much less frequently in the colon than in the upper gastrointestinal tract.

Submucosal tumors are primarily carcinoid and non-epithelial tumors. Based on the WHO classification and nomenclature of colorectal tumors, submucosal tumors can be classified as “nonepithelial tumors” and “carcinoid tumors” (Tab. 11.1).

**Table 11.1** Classification of submucosal tumors
Nonepithelial tumors
Benign tumors – leiomyomas, leiomyoblastomas – lipoma, lipomatosis – vascular tumors: hemangioma, lymphangioma Malignant tumors – leiomyosarcoma – other tumors
Carcinoid tumors

Clinical Picture and Clinical Significance

Submucosal tumors often remain asymptomatic, detected incidentally during endoscopic examination or radiology of the large bowel. Clinical manifestation is rare. Erosion of the mucosa can cause gastrointestinal bleeding and larger tumors may occlude the lumen; occlusion or tumor invagination may appear as an ileus (obstruction).

Diagnosis

Nonepithelial Tumors

Lipomas. Lipomas are the most frequently occurring submucosal tumors of the colon and rectum, comprising ca. 65% of all gastrointestinal lipomas. They are predominantly found in the right hemicolon and multiple tumors occur in 20% of patients. Incidence rates are 0.2-0.8% based on autopsy reports (3).

Lipomas appear as solitary or multiple submucosal lesions. They are rounded and elevated, 1-3 cm in size. Other endoscopic features include yellowish hue, smooth and translucent surface, and soft consistency ( 11.1 a-e). Lipomas are normally sessile; stalked lipomas are quite unusual ( 11.1 f, g). Their consistency can be tested with the instrument tip or biopsy forceps: if the lesion indents easily, this is referred to as a “pillow sign” ( 11.1) (5).

Excess adipose tissue occasionally accumulated at the Bauhin valve may make it appear to be a lipoma, though it is merely lipomatous. It is vital to recognize the difference in order to avoid resection of a lipomatous valve (Fig. 11.2). Endoscopic biopsy is only necessary if there is doubt about the identity of the lesion. Biopsy is indicated if the surface is irregular and/or eroded.

Repeated biopsies of a single lipoma may expose sensitive, yellow, adipose tissue underneath (Fig. 11.3

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