PMC8352713_01
Contrast-enhanced abdominal CT scan. Sagittal section. Enhanced abdominal CT shows a contrast effect on the perianal skin in the early phase.
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Regarding contrast-enhanced abdominal CT findings, in the early phase, contrast enhancement was observed in the skin around the anus, but there was no contributory finding in the intestinal tract between the anal canal and anal opening (Figure 1).
Endoscopic photograph of the lower gastrointestinal tract. (a) The mucous membrane of the anal canal was edematous and bled easily. (b) Redness and swelling with white moss were observed in the anus.
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The mucosa of the anal canal was edematous and hemorrhagic (Figure 2(a)). Redness and swelling with white moss were observed in the anus (Figure 2(b)).
Macroscopic image of the resected specimen surrounding the anus. There was a 92 mm x 48 mm tumor accompanied by slightly protruding white moss in the entire circumference of the anus with a clear boundary between the tumor and the surrounding healthy epithelium.
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There was a 92 mm x 48 mm tumor accompanied by slightly protruding white moss in the entire circumference of the anus with a clear boundary between the tumor and the surrounding healthy epidermis (Figure 3).
Histological images. (a) Histological image of the vicinity of the pectinate line of the anal canal showing the invasion of adenocarcinoma with tube formation directly under the stratified squamous epithelium. It was mucinous. Pagetoid cells, which are large clear cells, diffused into the stratified squamous epithelium. (b) Histological image of the area between the pectinate line and the opening on the rectal mucous side. Pagetoid spread of atypical cells was observed in the rectal epithelium. (c) A histological image of the squamous cell carcinoma around the anus. The anal skin region partially continued to the hair follicles, and it was complicated with well-differentiated squamous cell carcinoma invading the dermis.
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The histological findings revealed that an adenocarcinoma invaded the external anal sphincter and subcutaneous adipose tissue in the vicinity of the pectinate line of the anal canal (Figure 4(a)). The open portion of the anal canal was slightly invaded up to the rectal mucosa (Figure 4(b)). The anal adenocarcinoma skin region partially continued to the hair follicles and was complicated by squamous cell carcinoma invading the dermis (Figure 4(c)).
Immunohistochemical analysis of the resected adenocarcinoma around the anus. (a) Immunostaining for CK7. The adenocarcinoma directly under the squamous epithelium and atypical cells developing in the squamous epithelium was positive for CK7. (b) Immunostaining for CK19. The adenocarcinoma directly under the squamous epithelium and atypical cells developing in the squamous epithelium was positive for CK19. (c) Immunostaining for CK20. The adenocarcinoma directly under the squamous epithelium and atypical cells developing in the squamous epithelium was positive for CK20. (d) Immunostaining for CDX2. The adenocarcinoma directly under the squamous epithelium and atypical cells developing in the squamous epithelium was positive for CDX2. (e) Immunostaining of GCDFP15. The adenocarcinoma directly under the squamous epithelium and atypical cells developing in the squamous epithelium was negative for GCDFP15. (f) Immunostaining for MUC5A. The adenocarcinoma directly under the squamous epithelium was partially positive for MUC5A.
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Immunohistochemical analysis of the resected tumor around the anus revealed that the adenocarcinoma was positive for CK7, Cytokeratin 19 (CK19), CK20, and CDX2 (Figures 5(a)-5(d)), partially positive for MUC5A (Figure 5(f)), and negative for GCDFP15 (Figure 5(e)).
Immunohistochemical analysis of the squamous cell carcinoma in the anal skin region. (a) Immunostaining for p63. The atypical squamous epithelium was positive for p63 in all layers. Pagetoid cells diffusely present in the epithelium were negative. (b) Immunostaining for CK5/6. The atypical squamous epithelium was positive for CK5/6 in all layers. Pagetoid cells diffusely present in the epithelium were negative.
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Squamous cell carcinoma was positive for p63 (Figure 6(a)) and CK5/6 (Figure 6(b)) in all layers from the fundus to the surface layer.