PMC7264006_01
EUA + colonoscopy showed an 8 mm plaque just below dentate on left side of anal canal.
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Colonoscopy and examination of the anus under anaesthesia showed an 8 mm plaque on the dentate line that was biopsied (Fig. 1).
(a) Specimen shows high grade, poorly-differentiated small cell NEC (left) and adenocarcinoma (right) (H&E x20). (b) Large vessel venous invasion by small cell NEC (left) and glands lined by high grade adenocarcinoma (right) (H&E x20).
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Final histopathology reported a 1.3 cm poorly differentiated mixed adeno-neuroendocrine carcinoma (MANEC) of the anus (Fig. 2a-b).
Positive cytoplasmic membrane labelling of synaptophysin in small cell NEC with hyperchromatic nuclei, inconspicuous nucleoli and scant cytoplasm (x100).
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The neuroendocrine component was a small cell carcinoma which was positive for synaptophysin (Fig. 3) and chromogranin, with a Ki67 index of 80%.
Follow-up CT scan 6 months later demonstrating new liver metastases (axial and coronal views).
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CT scan at 9 months post presentation showed no evidence of anal tumour recurrence; however there were multiple bi-lobar liver metastases (Fig. 4).