A Rare Presentation of Papillary Carcinoma of Thyroid

Abstract

INTRODUCTION: Papillary thyroid carcinoma (PTC) is a follicular type of thyroid cancer most of time has lymphatic invasion and rarely has hematologic spread. This is a rare case leading to diagnosis of PTC from a right sided pleural effusion. CASE PRESENTATION:A 78 year old man with no significant past medical history presented with chief complain of cough with whitish phlegm, shortness of breath for past 3 days associated with choking sensation on eating. He is a former smoker. He was afebrile with normal blood pressure, tachypnic and was requiring 2 liter of oxygen. On physical examination he had poor breath sounds on right side of lung with no wheezes, crackle or rhonchi. On laboratory examination complete blood cell count, basal metabolic panel and pro b-type natriuretic peptide was within normal limit. Chest xray revealed right pleural effusion. Thoracocenthesis was done and 2 liters of serosanginous fluid was removed which was exudative with lymphocytic predominant on differential. He underwent computerized tomography (CT) of chest with contrast which showed mediastinal adenopathy, right sided pleural effusion. Later cytology from right pleural effusion came positive for adenocarcinoma (concern for non small cell lung cancer), with Positive: Pan keratin, CK7, TTF-1, Moc31. Positron emission tomography-PET-CT revealed hypermetabolic activities in cervical adenopathy, mediastinal adenopathy, pleural nodules and thyroid. He underwent left cervical lymph node biopsy which revealed metastatic papillary carcinoma with extra nodal extension and necrosis. Immunostains were positive for TTF-1 and thyroglobulin. Serum thyroglobulin antibody was greater than 500 IU/ml (normal < 4IU) and thyroid stimulating hormone 2.38 mcIU/ml (normal-0.350 3.74 mcIU/ml). Further pleural fluid pathology was correlated with the cervical biopsy pathology and diagnoses was reconsidered as PTC metastasis to lungs. DISCUSSION: PTC accounts for 80% to 90% of all thyroid cancers. Only 2 to 10 percent of patients have metastases beyond the neck at the time of diagnosis (1). Among such patients, two-thirds have pulmonary and one-fourth have skeletal metastases. From pathology standpoint, sometimes it becomes challenging to differentiate primary pulmonary adenocarcinoma (with papillary hisotlogy) from PTC as the histology shows well-differentiated branching papillae that mimics PTC. CONCLUSIONS: Our case based on pleural fluid pathology analysis initial presumptive diagnosis was considered as adenocarcinoma of lung. But later pleural fluid pathology was correlated with the cervical biopsy pathology and patient was diagnosed with PTC metastasis to lungs. Serum thyroglobulin and its antibody level are very helpful in diagnosis. In case of initial dilemma, one should also consider sending thyroglobulin level on pleural fluid analysis.