Oncocytic poorly differentiated (insular) thyroid carcinoma mimicking metastatic adenocarcinoma. A case report and review of the literature

Abstract

We report the cytohistologic and immunohistochemical findings of an oncocytic variant of poorly differentiated thyroid carcinoma in a 76‐year old man with a prior history of prostatic adenocarcinoma. The man complained of a palpable nodule in the right thyroid lobe and cervical lymph node. Fine‐needle aspiration (FNA) in both cases yielded solid clusters of cells/insulae, microfollicles, and isolated atypical cells. Considering the patient's past history, an initial diagnosis of metastasis from prostate adenocarcinoma was considered. However, immunohistochemical staining of liquid‐based cytology specimens (Thin‐Prep) showed diffuse positive results for TTF‐1 and thyroglobulin. The patient underwent total thyroidectomy with bilateral neck dissection. Histologic and immunohistochemical evaluation showed a poorly differentiated oncocytic thyroid carcinoma with lymphovascular invasion and lymph node metastases. To our knowledge, this is the first description of the immunocytochemical evaluation of this rare variant of poorly differentiated thyroid carcinoma using FNA and liquid based cytology.

The Long Journey towards Personalized Targeted Therapy in Poorly Differentiated Thyroid Carcinoma (PDTC): A Case Report and Systematic Review

“…Since cytological diagnosis of PDTC based on FNAC is challenging, our review has shown that some patients underwent a hemithyroidectomy or subtotal thyroidectomy with a completion thyroidectomy after histological diagnosis [ 38 , 44 , 52 , 54 , 59 , 65 , 69 , 85 , 103 , 104 , 107 , 108 , 115 , 117 ], but the majority of them were submitted to a total thyroidectomy as the initial operation [ 40 , 41 , 42 , 43 , 46 , 48 , 49 , 50 , 51 , 53 , 54 , 55 , 56 , 58 , 60 , 61 , 62 , 64 , 67 , 68 , 69 , 72 , 73 , 75 , 79 , 80 , 81 , 82 , 85 , 86 , 88 , 89 , 90 , 91 , 92 , 93 , 95 , 96 , 100 , 101 ,…”

Contribution of cytologic examination to diagnosis of poorly differentiated thyroid carcinoma

“…The small cell variant of MTC mimic resembles PDTC, Ewing sarcoma, lymphoma, metastatic carcinoma, or primary small cell carcinoma [17]. The small cell variant of MTC also exhibits granular plasmacytoid cytoplasm and a salt-andpepper-like nuclear chromatin pattern with occasional background amyloid; granular/coarse chromatin was reported in up to 95.5% of cases by Kane and Sharma [11] The oncocytic variant of PDTC should be distinguished from MTC, oncocytic (Hurthle cell) carcinoma, and metastatic carcinoma [15]. This rare variant of PDTC shows frequent small cell changes (as in case 2) and lymphoma, small cell carcinoma, and primary or metastatic neuroendocrine tumor should be included in differential diagnoses [17].…”

“…In addition, bare nuclei, polymorphonuclear leukocytes, and endothelial wrapping have also been suggested as ancillary diagnostic features [14]. In previous reviews of diverse cytologic studies, the most commonly reported FNA findings of PDTC were granular or salt-and pepper-like chromatin pattern, small cells with high N/C ratio, nuclear overlapping, and mild nuclear pleomorphism [15]. Thus, primitive, small tumor cells with scant cytoplasm and high N/C ratio are a key diagnostic feature of PDTC.…”

“…Thus, primitive, small tumor cells with scant cytoplasm and high N/C ratio are a key diagnostic feature of PDTC. The most important differential diagnoses of scattered small cells in PDTCs are papillary carcinoma and a small cell variant of MTC [14][15][16]. The classic morphology of MTC presents as epithelioid cells with occasional plasmacytoid appearance and focal spindle cell morphology.…”

Hurtle-cell carcinoma of thyroid gland: literature review and own data

“…Диференційна діагностика ГКК має включати медулярну карциному ЩЗ, метастатичні пухлини та онкоцитарну фолікулярну карциному [35]. Прове дення диференційної діагностики доброякісних та злоякісних новоутворень особливо утруднене у пе риоперативних умовах, коли стандартні критерії малігнізації (пенетрацію у капсулу, васкулярну інвазію) неможливо повністю оцінити [36].…”