SUN-490 Mass Cord Compression: Metastasis of Insular Thyroid Cancer

Abstract

Intro: Insular thyroid cancer is a rare and complex form of thyroid cancer, often referred to as poorly differentiated carcinoma. The exact incidence of insular thyroid cancers is difficult to assess due to controversial classification of this thyroid cancer over the years. It is termed poorly differentiated as it falls between the well-differentiated and undifferentiated carcinomas both morphologically and biologically[1]. Case: A 41 year old Hispanic female, with a history of prolactinoma and hyperparathyroidism, presented to the hospital with 10 days of progressive lower extremity weakness and paresthesias from T4 downwards, inability to bear weight, and no bowel movement for 12 days. MRI revealed a large thoracic soft tissue mass (7x4x4cm) centered in the posterior and medial aspect of the chest wall at T4-T5 with involvement of the spinal cord and vertebral bodies. She was also found to have a right sided thyroid mass (4.5x5x4 cm) with tracheal deviation- HerThyoid function test, were normal Intact PTH was 261, Thyroglobulin over 300, and Thyroid Antibodies were negative. Patient underwent T3-T6 laminectomy, T2-T7 fusion, and T4-T5 tumor resection, which was subtotal due to vascularity. Second procedure included a right thoracotomy, chest wall resection of ribs 4 and 5 with full resection of paraspinal mass, total thyroidectomy, parathyroidectomy with central cervical lymphadenectomy. Pathology results of paraspinal mass showed insular thyroid carcinoma. Post operatively, the patient reported improvement of sensation and strength in lower extremities. Genetic testing for MEN syndrome was negative. Discussion: Insular thyroid carcinoma, also referred to as poorly differentiated carcinoma is a rare form of thyroid cancer. Insular carcinoma was characterized by to include the following complex histologic features, “formation of solid clusters (insulae) of tumor cells containing a variable number of small follicles; variable but consistently present mitotic activity, capsular and blood vessel invasion; and frequent necrotic foci, sometimes leading to formation of peritheliomatous patterns”[1]. The cells originate from follicular epithelium and possess the potential to concentrate radioiodine[2]. Unlike anaplastic carcinoma of the thyroid, p53 and p21 staining was negative in insular carcinomas[3]. Thyroglobulin staining is generally positive[4]. Distant metastasis occurs in about 31% of patients with insular thyroid carcinoma[5]. In cases of distant metastasis, treatment with thyroidectomy and radioiodine therapy were shown to independently improve survival[5]. The Constellation of Insular thyroid cancer, hyperparathyroidism and Prolactinoma, has not been reported before. References: [1]. Am J Surg Pathol. 1984;8:655- [2] J of Nuc Med 32(7), 1358 [3] Ann of Surg vol. 231,3 (2000): 329 [4] JCEM 99. 1167–9. 10.1210/jc.2014 [5] Cancer. 2012 Jul;118(13) 3260