Summary

A 68-year-old man diagnosed with cT3N2 adenocarcinoma of the rectum presented with a synchronous solitary liver metastasis on CT scan. Neoadjuvant chemoradiotherapy was started to downstage the primary tumour. Resection of the rectal tumour followed 3 months after the last radiotherapy session and primary resection of the isolated liver lesion was performed in the intervening period. Histopathological assessment of the liver lesion, however, showed no malignancy, but did reveal a necrotic infection due to Enterobius vermicularis. This parasite is frequently found in the intestines, but only rarely infects the liver. The patient was subsequently treated with the anthelmintic drug mebendazole 100 mg once a week for 2 weeks. Histopathological assessment of the rectal specimen showed complete regression after neoadjuvant chemoradiotherapy without evidence of remaining E. vermicularis, suggesting pinworm eradication. The patient recovered promptly after both surgical procedures.