View Abstract

A4006 - Metastatic Adenocarcinoma in the Thyroid with Two Known Primaries - A Diagnostic Challenge
Author Block: H. Grewal1, S. Gupta1, A. Singh1, T. King2; 1Internal Medicine, Saint Vincent Hospital, Worcester, MA, United States, 2Pathology, Saint Vincent Hospital, Worcester, MA, United States.
INTRODUCTION: Malignancies with intra-thyroid metastases are rare, clinically representing less than 4% of all thyroid malignancies and most common cancers to metastasize are renal, lung, breast and melanoma.
CASE PRESENTATION: A 71-year- old female with history of right breast adenocarcinoma status post lumpectomy and endometrial carcinoma status post hysterectomy / chemo-radiotherapy, on PET
surveillance was noted to have an FDG avid interval increase in left upper lobe pleuro-parenchymal opacity to 1.7cm with multiple mediastinal FDG-avid nodes. Due to new constitutional symptoms she underwent VATS biopsy with pathology being positive for stage 3 poorly differentiated adenocarcinoma.
She was treated with carboplatin/paclitaxel with radiation therapy. She poorly tolerated chemotherapy with recurrent infections, acute kidney injury and gastrointestinal intolerance. In the year to follow, her clinical course was complicated by deep vein thrombosis, pulmonary embolism, small bowel obstruction, dysphagia, clostridium difficle colitis and radiation esophagitis, each event leading to an admission.
PET-CT, an year from diagnosis revealed bilateral FDG-avid lower neck, supraclavicular, superior mediastinal, right paratracheal, subcarinal lymphadenopathy with an increased left paramediastinal FDG avid 4.1 cm mass. There was new focal uptake in the left breast and left axillary lymph nodes. A breast biopsy was positive for ER / PR / HER2 negative, TTF-1 positive invasive ductal carcinoma.
A heterogeneous thyroid gland with an interval increase in left lobe nodule led to a fine needle aspiration (FNA) revealing malignant epithelial cells with immunohistochemistry (IHC) demonstrating focal positivity for Napsin A, negative for thyroglobulin or ER / PR. She had progressive disease with extensive metastatic foci found on thoracic spine and bilateral femoral heads, putting her at high risk for pathological fractures. She denied any orthopedic intervention and was transitioned to hospice care.
DISCUSSION: Intra-thyroid metastasis in the presence of two active malignancies has not been reported to the best of our knowledge, and may confound the origin of metastases. The rarity of ITM makes it imperative to differentiate it from primary thyroid malignancies and IHC proves beneficial here. The clinical and radiological criteria are ill-defined and need better characterization.
CONCLUSIONS: Increased clinical awareness of ITM and a histopathological evaluation is an essential tool to improve preoperative diagnosis of thyroid nodule associated with extra-thyroid malignancy and could avoid unnecessary thyroidectomy in polymetastatic disease with poor prognosis.