case_images: PMC9968506_01
case_images: Abdominal CT scan showing a large obstructing solid mass arising from the sigmoid colon (arrow), measuring approximately 6 cm x 5.5 cm.
case_images: cureus-0015-00000034283-i01.jpg
case_images: PMC9968506_01_cureus-0015-00000034283-i01.jpg
case_images: FIG1
case_images: A computed tomography (CT) of the abdomen was performed and revealed a large circumferential and stenosing mass of the sigmoid measuring approximately 6x5.5 cm (Figure 1).
case_images: Photomicrograph image showing histological with hematoxylin and eosin stain and immunohistochemical features of squamous cell carcinoma of the sigmoid: (A) (Low magnification) showing normal colonic mucosa (red star) with adjacent moderately differentiated keratinizing squamous cell carcinoma (black arrow). (B) (High magnification) showing large polygonal tumor cells, showing hyperchromatic, anisocaryotic nuclei with figures of mitosis. The cytoplasm was abundant and eosinophilic. (C): The cancer cells were positive for P40 (immunohistochemistry (IHC), 20 x). (D): The cancer cells were positive for CK5/6 (IHC, 20 x); (E): The cancer cells were negative for CDX2 with positive internal control of colonic mucosal epithelial cells (IHC), 20 x).
case_images: cureus-0015-00000034283-i02.jpg
case_images: PMC9968506_01_cureus-0015-00000034283-i02.jpg
case_images: FIG2
case_images: Histopathology sections (Figures 2A, 2B) showed a colonic mucosa largely infiltrated by a carcinomatous tumoral proliferation consisting of sheets and nests of large polygonal tumor cells, showing hyperchromatic, anisocaryotic nuclei with figures of mitosis. Immunohistochemically, the tumor cells were positive for the squamous markers CK5/6 and p40 (Figures 2C, 2D). They were negative for CDX2 (Figure 2E).