Evidence for colorectal sarcomatoid carcinoma arising from tubulovillous adenoma

Figure 1 Colonoscopy demonstrates. A: Large sessile polypoid growth with velvety surface and superficial ulceration in the rectum (forward view); B: Multilobulated, smooth surfaced exophytic nature of the tumor upon retroflexion. Sonographic images at rectal EUS showing; C: An infiltrative mass with invasion of the muscularis mucosa (star); D: An 8-mm hypoechoic lymph node suspicious for lymphatic metastasis (arrow).

Figure 2 Histology of the rectal biopsy using HE stains. A: Tubulovillous adenoma and underlying spindle cell tumor. The aggressive spindle cell lesion infiltrates directly underneath the adenoma (× 10); B: A higher magnification view of the adenomatous component (× 20). High-grade spindle cell lesion (× 40) showing: C: Cigar shaped nuclei, nuclear pleomorphism, a high mitotic rate; D: Tumor necrosis; E: Smooth muscle-like spindle sheets of cells in the sarcomatoid component (× 40).

Figure 3 Gross appearance of the surgically-removed rectosigmoid mass (A and B). A: The luminal side view demonstrates the proximity to the dentate line; anal skin is labeled for orientation; B: Upon sectioning the sample through the sagittal plane, the lateral view identifies the sarcomatoid smooth component (marked as S) underneath the velvety tubulovillous adenoma component (marked as TVA); C: Invasive adenocarcinoma with high nucleus/cytoplasm ratio within the deeper sections; D: Pancytokeratin was diffusely positive in both epithelial and mesenchymal components (× 20); E: Vimentin showed expression in the sarcomatous (S) component only, with no staining in the carcinoma (C) portion.

Figure 4 Immunohistochemical characteristics of the resected tumor showed. A: p53 was expressed in both carcinomatous (C) and sarcomatous (S) components within the tumor, with a relative increase in the latter; B: Staining for CD117 was negative; C: PDGFR stained diffusely positive in both the components (× 20).