Pinworm infection masquerading as colorectal liver metastasis.

Enterobius vermicularis is responsible for a variety of diseases but rarely affects the liver. Accurate characterisation of suspected liver metastases is essential to avoid unnecessary surgery. In the presented case, following a diagnosis of rectal cancer, a solitary liver nodule was diagnosed as a liver metastasis due to typical radiological features and subsequently resected. At pathological assessment, however, a necrotic nodule containing E. vermicularis was identified. Solitary necrotic nodules of the liver are usually benign but misdiagnosed frequently as malignant due to radiological features. It is standard practice to diagnose colorectal liver metastases solely on radiological evidence. Without obtaining tissue prior to liver resection, misdiagnosis of solitary necrotic nodules of the liver will continue to occur.