Isolated metastasis to small bowel from anaplastic thyroid carcinoma. With a review of extra-abdominal malignancies that spread to the bowel.

Symptomatic involvement of the small bowel by isolated metastasis from an extra-abdominal primary malignancy is rare, most commonly resulting from malignant melanoma and lung cancer. A few other extra-abdominal tumors, not including thyroid cancer, have been documented on rare occasions to present with small-bowel involvement as the first evidence of metastasis. We report a case of anaplastic thyroid carcinoma with isolated symptomatic metastasis to the small intestine. We review the literature regarding the frequency and origin of extra-abdominal malignancies developing small-bowel metastases and the spectrum of clinical manifestations resulting from this syndrome.