1. Kikuchi-Fujimoto Disease Masquerading as Metastatic Papillary Carcinoma of the Thyroid Manuel Villa, MD 1, Shailesh Garg, MD 1, Thomas Mathew, MD 1, Louis-Joseph Auguste, FACS, MD 1 Northshore-Long Island Jewish Health System, Manhasset, New York 1 References 1.Clinical outcome and predictive factors of recurrence among patients with Kikuchi's disease. Int_J_Infect Dis. 2009 May; 13(3):322-6. Epub 2009 Feb 8. 2.Kikuchi-Fujimoto Disease. Arch Pathol Lab Med-Vol 132, Feb 2010 3. Kikuchi’s Disease: A Rare Cause of Fever and Lymphadenopathy. Clinical Medicine Insights: Pathology 2012:5 4. Kikuchi's disease (histiocytic necrotizing lymphadenitis). A clinicopathologic study of 79 cases with an analysis of histologic subtypes, immunohistology, and DNA ploidy. Kuo TT. Am J Surg Pathol. 1995 Jul;19(7):798-809. Abstract Kikuchi-Fujimoto disease also known as histiocytic necrotizing lymphadenitis is a rare cervical inflammatory lymphadenitis, most commonly seen in young Asian women, although it might be associated with autoimmune diseases and commonly follows a self-limited course. We present an unusual case of Kikuchi-Fujimoto disease masquerading as metastatic papillary carcinoma of the thyroid. A 30-year-old young female presented 2 months post-partum with complaints of neck pain and fever with CT scan showing enlarged right- sided lymph nodes with a thyroid nodule. A subsequent biopsy of the thyroid nodule showed papillary thyroid carcinoma and reactive inflammation of the lymph node. She was electively taken for surgery when a total thyroidectomy, central node dissection and a right modified lymph node dissection was performed for enlarged lymph nodes. After an uneventful recovery, pathology came back as papillary carcinoma of thyroid with one metastatic lymphadenopathy and several other lymph nodes with histiocytic necrotizing lymphadenitis. This co-existence of Kikuchi-Fujimoto disease with metastatic papillary thyroid cancer at presentation is unusual and presents a challenging and complex management dilemma. Introduction Initially described in 1972, Kikuchi-Fujimoto disease is a rare and uncommon clinical condition most commonly affecting young women in 3 rd and 4 th decades and presents typically as cervical lymphadenitis with low-grade fever, malaise, and fatigue although generalized disease has been reported. The differential diagnosis is broad and disease can mimic as lymphoma, tuberculosis, metastatic disease, SLE, cat scratch disease and infectious mononucleosis. Definitive diagnosis is made by lymph node biopsy showing unique patchy, irregular areas of eosinophilic necrosis in the paracortex. The disease is self-limited and symptoms resolve within 1-6 months with no real effective treatment. Case Presentation Discussion Our patient is a 30-year-old female of Indian origin with no significant past medical history who initially presented to her PMD for neck pain, swelling, fever and fatigue that was treated as upper respiratory infection with antibiotics. With no improvement in her symptoms and increased neck swelling with palpable lymph nodes, an ultrasound and CT scan was done showing extensive right neck lymphadenopathy and an 8 x 6 mm right thyroid nodule. Blood work showed elevated monocytes and elevated TSH of 13.36 mIU/ml. Kikuchi-Fujimoto disease is a histiocytic necrotizing lymphadenitis which is a rare and benign condition that has been mainly described in women younger than 40 years of age. It has been described in men too and practically all ethnic groups though more commonly in Asian people. It can mimic other diseases such as lymphoma, tuberculous adenitis, metastatic disease, SLE, cat scratch disease and infectious mononucleosis. The pathogenesis is unclear but is believed to be an immune response of T cells and histiocytes to an unknown inciting agent such as EBV, HHV 6 & 8, HIV, toxoplasma and paromyxoma viruses. Cellular destruction is hypothesized to be due to apoptotic cell death mediated by CD8 T lymphocytes. It usually presents with fever, fatigue, weight loss, painful cervical lymphadenopathy, arthritis and sometimes rash. Lymphadenopathy is usually cervical but may involve axillary, mediastinal, and iliac nodes. Anemia, leukopenia, and elevated ESR can be seen on laboratory studies. Lymph node biopsy needs to be done to confirm the disease & to exclude other serious disorders like metastatic disease and lymphoma. Pathology usually shows necrotic foci on gross examination and paracortical foci with histiocytic infiltrate on microscopic examination. Although uncommon, a recurrence rate of 3-7% has been reported. Signs and symptoms usually resolve in 2 to 6 months and there is no effective treatment though high dose glucocorticoids with intravenous immunoglobulin have been shown to be of some benefit. The coexistence of Kikuchi disease and papillary thyroid cancer in this patient presented a complex and challenging clinical scenario especially, the decision to perform a neck dissection for clinically positive nodes despite FNA showing reactive changes and the intraoperative decision regarding how extensive should the node dissection be. In summary, although Kikuchi’s disease is a rare entity, we should consider it in the differential diagnosis when a young woman presents with fever and cervical lymphadenopathy. Radiologic Findings With no significant past medical history of SLE, tuberculosis, lymphoma or autoimmune disorder, her presumptive diagnosis was thyroid cancer with possible metastasis with coexisting viral infection. She underwent thyroid nodule FNA and lymph node biopsy that showed papillary thyroid cancer and reactive inflammatory changes in the lymph node. Subsequently, she underwent a total thyroidectomy with central node dissection and a right radical modified lymph node dissection that proceeded uneventfully. During her surgery she had extensive lymphadenopathy that resulted in a type III comprehensive neck dissection encompassing submandibular gland and lymph nodes level I to VI. Pathology showed papillary carcinoma of thyroid with one positive lymph node and remaining lymph nodes showing necrotizing histiocytic lymphadenitis. Patient recovered well from her surgery and underwent radioactive iodine I-131 treatment postoperatively with post therapy whole body I-131 scan demonstrating no iodine avid tissue in the thyroid bed. Pathologic Findings Sternocleidomastoid Submandibular Space Digastric Muscle Intraoperative Image Right Neck dissection Papillary Carcinoma of thyroid gland Metastatic carcinoma of the lymph node Histiocytic necrotizing lymphadenitis Neck Ultrasound showing 6 x 8 mm right thyroid nodule Sagittal CT View of Neck showing right thyroid nodule – 6 mm Coronal CT View of Neck showing right sided level V lymphadenopathy Transverse CT View of Neck showing right thyroid nodule and right-sided lymphadenopathy