Extra-osseous Ewing sarcoma of the thyroid gland mimicking a hemorrhagic cyst of Hashimoto thyroiditis

Abstract

Ewing’s family of tumors, including Ewing sarcoma, Askin tumor, and peripheral primitive neuroectodermal tumors, were first identified by James Ewing in 1921. Ewing sarcoma is more common in bones. However, extraosseous Ewing sarcoma (EoES) is a very rare separate entity and was first described by Tefft and al. in 1969. It is a highly malignant round-cell tumor and contains a reciprocal translocation between chromosomes 11 and 22, t(11;22). In this report, we present the case of a 34 years old female patient who was unfortunately diagnosed with Ewing sarcoma of the thyroid after being operated for a hemorrhagic cyst in a context of Hashimoto thyroiditis.The patient was followed at the endocrinology department for an auto-immune thyroiditis for two years. She complained of neck pain and a suspicious hemorrhagic cyst was discovered on thyroid ultrasound. She underwent total thyroidectomy; three weeks later, she suffered from right sided firm swelling in her neck. The pathology was in favor of EoES of the thyroid. To date and to the best of our knowledge, this is the first case of Ewing sarcoma of the thyroid in auto-immune thyroiditis. EoES of the thyroid is a very rare entity and should be considered in the differential diagnosis of a solid tumor in the thyroid. Diagnosis is based on ultrastructural examination, immunostaining and evidence of abnormal translocation t(11;22). It is usually an aggressive disease.Early diagnosis with adequate surgical management and chemotherapy are the mainstay of the treatment and may change the outcome.