Unusual case of a submucosal tumor in the sigmoid colon. Gastrointestinal elastosis.

A 46-year-old man was referred to the Department of Gastroenterology at Toranomon Hospital, Tokyo, following a positive result in a fecal occult blood screening test. The patient presented no unusual physical findings, and there were no abnormal results in laboratory tests. Neither he nor his family had a notable medical history. Colonoscopy showed a submucosal tumor (SMT) in the sigmoid colon. The tumor was pale yellow with a smooth surface, elastic, and hard as a result of expansion; it was approximately 4 mm in diameter [Figure 1]. Endoscopic ultrasonography demonstrated that the tumor was a slightly hypoechoic mass, arising from the second layer of the bowel wall [Figure 2]. We suspected that it was a carcinoid tumor, although echogenicity of the SMT was slightly high for a carcinoid tumor. Incisional biopsy would have been a feasible option. However, we directly performed an endoscopic submucosal dissection for a complete excisional biopsy after receiving informed consent from the patient. He was subsequently discharged from our hospital without complications.

Figure 1

Endoscopic image

Figure 2

Endoscopic ultrasonographic image

QUESTION

What is the diagnosis of this SMT?

ANSWER

Histopathology of the resected tumor revealed that the lamina propria and muscularis mucosa were diffusely replaced by a rounded mass with a homogeneous or fibrillar deposit, which appeared slightly basophilic [Figure 3]. The mass was dark gray with elastic staining; some parts of the mass, which presumably consisted of vascular wall and muscularis mucosa, had a deep-black appearance [Figure 4]. This finding was consistent with that of elastosis in previous studies.[123]

Figure 3

Microscopic image (stain, hematoxylin and eosin)

Figure 4

Microscopic image (stain, Elastica van Gieson)

Reports of gastrointestinal elastosis are rare. However, the lesions have shown various types of endoscopic configurations[1]—mostly small polyps,[2] especially in the rectosigmoid colon.[1] This benign configuration of elastosis may have caused gastroenterologists to pay little attention to gastrointestinal elastosis in the past. Several studies published in the 2000s suggested that gastrointestinal elastosis is not as rare as generally believed.[23]

To our knowledge, the present report is the first to show endoscopic ultrasound imaging of gastrointestinal elastosis. The lesion clearly appeared as a slightly hypoechoic mass arising from the second layer; it did not invade the muscularis propria, and it was important that we knew this before performing the endoscopic submucosal dissection. In addition, the present report suggests that echogenicity of the gastrointestinal elastosis was slightly higher than that of a carcinoid tumor. More cases of gastrointestinal elastosis should be investigated to confirm our findings. The patient was discharged from our hospital without complications, and there has been no recurrence.