Lytic sternal mass: an unusual clinical presentation of papillary thyroid microcarcinoma
Merve Kutahyalioglu, MD1,2, Eiman Yehia Ibrahim, MD2, Mark Zafereo, MD3, Michelle D Williams, MD4 and Naifa L Busaidy, MD2
(1)Division of Diabetes, Endocrinology and Metabolism, Baylor College of Medicine, Houston, TX, (2)Department of Endocrine Neoplasia and Hormonal Disorders, The University of Texas MD Anderson Cancer Center, Houston, TX, (3)Department of Head and Neck Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, (4)Department of Pathology, University of Texas MD Anderson Cancer Center, Houston, TX
Papillary thyroid carcinoma is the most common type of thyroid cancer and commonly spreads via lymphatics to lymph nodes. After the lungs, the second most common distant site metastasis is the bone which usually occurs in patients with large primary tumors with nodal involvement. Sternal metastasis at initial presentation is extremely rare. In this report we present an elderly woman presenting with osteolytic sternal mass which led to the diagnosis of metastatic papillary thyroid cancer follicular variant from a primary microcarcinoma.
An 80-year woman presented with a slowly enlarging mass over the sternum for 1.5 years. Cross sectional imaging of the chest revealed a large soft tissue mass within the sternum causing lysis of the bone (Fig 1). Core biopsy of the sternal mass was obtained and pathologic examination showed thyroid follicular neoplasm with hurthle cell changes. For staging purposes, she underwent ultrasonography of the neck and cross sectional imaging of the neck, chest, abdomen and pelvis, which showed a multi-nodular thyroid gland with dominant left inferior 1.9 cm thyroid mass, mediastinal lymphadenopathy, nonspecific small pulmonary nodules, nonspecific liver nodules and aforementioned lytic expansile upper sternal mass. Positron emission tomography–computed tomography showed FDG avidity only in the sternal mass and mediastinal lymph nodes only. A nuclear bone scan only identified the sternal metastasis (Fig 2). The patient underwent total thyroidectomy and manubrial resection with en bloc clavicular head and first and second ribs with free flap reconstruction surgery. Pathological examination revealed a 1 millimeter follicular variant papillary microcarcinoma in the thyroid gland with a 5.5 centimeter papillary thyroid carcinoma sternal bone metastasis involving skeletal muscle and R0 resection margins. The patient’s disease was classified as stage IVC papillary thyroid cancer (T1aN0M1). Post-operative thyroglobulin and thyroglobulin antibody levels were undetectable (Table 1). Stimulated whole body nuclear medicine diagnostic scan showed a small iodine avid remnant (0.3 percent uptake) only in the thyroid bed and she was treated with 50 mCi of I-131 sodium iodine (Fig 3).
In this case we report an unusual presentation of bone metastasis from a papillary thyroid microcarcinoma. While papillary thyroid microcarcinoma often has an indolent growth pattern, in rare cases, distant metastases can occur even in the absence of loco-regional lymph node involvement.