Incidental Poorly Differentiated Thyroid Cancer in Trauma Patient

Abstract

Poorly differentiated carcinomas tend to arise de novo or transform from differentiated thyroid carcinomas. Females, middle-aged and elderly adults are most commonly affected. Patients present with an enlarging thyroid mass which is often locally advanced at presentation. This is a case of 30-year-old male patient admitted after burn injury who presented with neck enlarging mass. He had no family history of thyroid CA, no radiation exposure and normal thyroid function tests. Neck CT imaging found with heterogeneous enhancing mass arising from the left thyroid lobe. Thyroid ultrasound consistent with a large left thyroid lobe lesion described as a complex solid component measures at least 5.2 cm long x 4.0 cm AP by 5.0 cm transverse with coarse scattered echogenic foci, and smaller bright echoes with comet-tail artifacts. Fine needle biopsy was non-diagnostic or unsatisfactory. Second FNA with Atypia of undetermined significance. Left hemithyroidectomy performed consistent with a 5cm Poorly differentiated thyroid carcinoma arising in a preexisting papillary thyroid carcinoma with extensive necrosis, pT3aNx, TTF1 +, PAX 8 +, CK7 +. Right thyroid was negative for malignancy. A Therapeutic dose of 135.7 mCi of 131-iodine was given. Subsequent whole body scan with focal findings in the thyroid bed region is consistent with residual functional thyroid tissue. Follow up with normal thyroglobulin levels and negative thyroglobulin antibodies. Neck ultrasound without abnormal tissue or nodules seen at either thyroid bed. Follow up with 18-F-FDG PET/CT scan abnormal study with avid lymph node in the right side of the neck, Level 3. FNA lymph node, cervical right level 3, 1.1cm, ultrasound guided biopsy negative for metastatic carcinoma. Poorly differentiated thyroid carcinomas present as large thyroid masses. The tumor spreads by local invasion into perithyroidal tissues and by distant metastases. Poorly differentiated carcinoma is supported by immunohistochemical staining for Tg, TTF1, and paired box protein Pax 8 (PAX8). There is no standardized treatment for PDTC to date. If possible, a total thyroidectomy including lymph node dissection should be performed to improve survival rates. Due to the higher rate of ETE, positive margins, neck disease, and distant metastases, adjuvant treatment should be considered. Some experts recommended considering adjuvant RAI in all PDTC patients, giving the potential benefit and lack of morbidity. However, despite the capability of RAI uptake in a high percentage of PDTC, no significant impact on survival has been reported. It is important to recognize prognosis of PDTC is distinctly less favorable than that of PTC or FTC. Several factors have been identified to affect patient prognosis such as extensive tumor necrosis, >45 year of age, tumor size (>5 cm), extrathyroidal extension and distant metastases are unfavorable prognostic factors.