Thyroid implants after surgery and blunt trauma.

The differential diagnosis of thyroid tissue found laterally in the neck includes several conditions: lymph node deposits of thyroid carcinoma, "benign metastatic thyroidosis," detached thyroid nodules, and true ectopic thyroid tissue. We have studied nine cases with thyroid deposits in the soft tissues of the neck that do not conform to these diagnoses. We present evidence that they represent surgical or traumatic implantation of thyroid neoplasms. Eight of the nine cases presented one to 26 years after initial surgery. Adequate information of the operative procedure was available in seven cases, one patient underwent subtotal lobectomy and six subtotal thyroidectomy for a nodular gland. The nodules occurred within the operation field with no evidence that they were within lymph nodes. In six cases, birefringent particles consistent with talc from the earlier operation were found adjacent to the nodules. Three cases showed implants of colloid nodules, three of follicular adenoma, one of oncocytic (Hürthle) cell adenoma and one of follicular carcinoma. In the ninth case, infiltrating thyroid tissue in muscle and fibrous tissue presented 3 years after major blunt trauma to the neck. The tissue resembled that in a disrupted thyroid nodule present in the gland itself and was regarded as traumatically implanted. The observation that surgery or trauma to a nodular thyroid can occasionally lead to multiple subcutaneous thyroid implants has implication for management of thyroid disease. Therapy may be difficult; recurrence followed surgical removal of the nodules in three cases, and radioiodine may be a more effective therapy. Recognition of this entity is important for accurate pathologic diagnosis. It is apparently limited to implantation of tumor. The absence of implantation of normal or hyperplastic thyroid, despite the high frequency of partial thyroidectomy in Graves' disease, has pathobiological implications. These findings also support the generally held view that lobectomy rather than nodulectomy is the operation of choice for a solitary nodule.