BRIEF REPORT Poorly differentiated thyroid carcinoma with pleomorphic giant cells—a case report Alexia Gazeu 1 & Jonathan Lopez 2,3 & Serge Guyetant 4 & Manuel Sobrinho-Simoes 5,6,7 & J. C. Lifante 8 & Christine Cugnet-Anceau 9,10 & Myriam Decaussin-Petrucci 1,11,12 Received: 15 November 2019 /Revised: 10 March 2020 /Accepted: 25 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Poorly differentiated thyroid carcinoma (PDTC) refers to a malignant tumour that displays an intermediate prognosis between well-differentiated carcinomas and anaplastic thyroid carcinomas (ATC). In the thyroid, pleomorphic giant cells are observed in ATC or in some non-neoplastic thyroid diseases. We described the case of a 43-year-old woman with a 34-mm nodule in her thyroid right lobe. Microscopic examination revealed an encapsulated tumour with a main solid growth pattern and extensive capsular invasion. Multiple images of angioinvasion were observed. There was neither necrosis nor inflammation. Most of the tumour cells were medium-sized and intermingled with pleomorphic giant tumour cells with bizarre features. The immunoprofile (keratins +, TTF1+, Pax 8+) proved their thyroid origin. By NGS, no molecular alteration was identified. The patient was treated by surgery and radioiodine therapy and she has no recurrence after a follow-up of 24 months. Our case meets all the histological criteria of the Turin proposal for PDTC but with pleomorphic giant cells and is very different from ATC according to clinical, histological and immunohistochemical features. Pleomorphic tumour giant cells in thyroid carcinomas could be present in PDTC and do not always represent dedifferentiation and more aggressive carcinoma, thyroid neoplasm. Keywords Thyroid neoplasm . Poorly differentiated thyroid carcinoma . Pleomorphic giant cells . Anaplastic thyroid . Carcinoma Introduction Thyroid carcinoma of follicular cell origin represents a spec- trum of tumours ranging from indolent tumours such as well- differentiated carcinomas to aggressive malignancies like an- aplastic thyroid carcinomas (ATC). The term “poorly differ- entiated thyroid carcinoma” (PDTC) refers to a malignant tu- mour that displays an intermediate prognosis between these * Myriam Decaussin-Petrucci myriam.decaussin-petrucci@chu-lyon.fr 1 Pathology Department, Centre Hospitalier Lyon-Sud, Hospices Civils de Lyon, Pierre-Bénite, France 2 Biochemistry and Molecular Biology Department, Centre Hospitalier Lyon-Sud, Hospices Civils de Lyon, Pierre-Bénite, France 3 Cancer Research Center of Lyon, Team EMT and Cancer Cell Plasticity, Lyon 1 University, Villeurbanne, France 4 Department of Pathology and Tumor Biobank, Centre Hospitalier Régional Universitaire de Tours, Tours, France 5 Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal 6 Medical Faculty, University of Porto, Porto, Portugal 7 Department of Pathology, Hospital de S. João, 4200-319 Porto, Portugal 8 Endocrine Surgery department, Centre Hospitalier Lyon-Sud, Hospices Civils de Lyon, Pierre-Bénite, France 9 Department of Endocrinology and Diabetes, Hospices Civils de Lyon, Lyon-Sud Hospital, Pierre-Bénite, France 10 ImmuCare (Immunology Cancer Research), Hospices Civils de Lyon, Lyon, France 11 Cancer Research Center of Lyon, INSERM1052 CNRS5286, Lyon 1 University, Villeurbanne, France 12 Département de Biopathologie Sud, Hospices civils de Lyon – Centre Hospitalier Lyon Sud, 165 Chemin du Grand Revoyet, 69495 Pierre-Bénite, France Virchows Archiv https://doi.org/10.1007/s00428-020-02807-7