PMC5088540_01
Colonoscopy shows an elevated tumor with an unclear boundary and small ulceration in the descending colon. A small polyp at the opposite site is an inflammatory polyp.
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Surveillance colonoscopy was regularly performed, and an elevated tumor measuring 15 mm in diameter with a small ulceration was noted in the descending colon in July 2011 (Fig. 1).
The tumor gradually progressed to resemble type-2 cancer after fourteen months.
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The tumor gradually progressed to resemble type-2 cancer after 14 months of observation (Fig. 2).
Endoscopic findings before the operation. Endoscopic ultrasonography shows a tumor of the submucosal layer, and the compressed muscle layer (A). The tumor demonstrates growth similar to type 2 cancer (B).
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Endoscopic ultrasonography revealed that the tumor was located mainly in the submucosal layer, and the muscle layer was compressed (Fig. 3A). A pathological examination detected no cancer cells, despite the continued growth of the tumor after 18 months (Fig. 3B).
Resected specimen of the descending colon. The elevated tumor which resembles type-2 cancer measures 4.0x3.2 cm in size (A). Low-power magnification of the specimen stained with Hematoxylin and Eosin staining (H&E, x1) showing the transmural tumor with an ulcerated superficial mucosa (B).
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The gross appearance and low-power magnification of the specimen showed a protruded transmural tumor with ulceration (Fig. 4).
Pathological examinations of the tumor mainly composed of spindle cells having eosinophilic cytoplasm and cigar-shaped nuclei with a blunt end (Hematoxylin and Eosin staining, x200).
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The tumor was mainly composed of spindle cells having eosinophilic cytoplasm and cigar-shaped nuclei with a blunt end (Fig. 5).
Immunohistochemistry showing that the tumor is positive for alpha-smooth muscle actin (A) and desmin (B), and negative for c-KIT (C), DOG-1 (D), CD34 (E), and S-100 (F) (x40).
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Immunohistochemical staining was positive for the conventional smooth muscle markers of alpha-smooth muscle actin and desmin, and entirely negative for c-KIT, DOG-1, CD34, and S-100 (Fig. 6).