ECP 2023 Abstracts

S247 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 *G.E. Palade UMFST Targu Mures, Romania Background & objectives: BRAFV600E is the most common genetic mutation in PTC (papillary thyroid carcinoma). We performed a molecular and immunohistochemical (IHC) study to validate the IHC technique in detecting the BRAFV600E mutation, comparing it to the molecular PCR technique, considered as reference. Methods: We stained 50 formalin-fixed PTC specimens using the monoclonal antibody anti-BRAFV600E clone VE1: 35 BRAFV600E positive and 15 BRAFV600E negative confirmed by PCR. Clinical information (age at diagnosis, sex, date of surgery) and pathological data were obtained from medical records. The sensitivity and specific- ity of the anti-BRAFV600E antibody were assessed. Results: IHC of BRAFV600E showed 94.4% sensitivity and 66.7% speci- ficity. Of 35 BRAFV600E PCR-positive PTC samples, 33 (94.3%) cases expressed the anti-BRAFV600E antibody too with cytoplasmic weak (45.5%), moderate (39.4%), and strong (15.2%) immunostaining. Of the 15 BRAFV600E PCR-negative PTCs, 66.7% (10/15) were also IHC nega- tive. Five PCR-negative PTC showed positive immunostaining with weak (20%), moderate (60%) and strong (20%) intensity. Of these cases, 3 were observed in the Warthin-like variant and 2 in the tall cell variant. Conclusion: BRAF IHC is a feasible and easily reproducible method. However, the presence of false positive and false negative results in our study group (similar to the data in the literature), highlights the need for caution when relying solely on one method for detecting BRAFV600E mutation. When there is a strong suspicion of the mutation being pre- sent, based on morphological criteria (certain histological variants, lymph node metastases, extrathyroid extension), using both methods would be an ideal approach. Funding: FDI internalization of higher education E-PS-09-011 Hypercalcemia in the debut of two parathyroid carcinomas in young patients S. Haro Yuste*, F. Leiva-Cepas, I. Sánchez Ramírez, J. Osuna Soto, M.J. Galvez Medina, A. Sanz Zorrilla *Hospital Universitario Reina Sofía, Spain Background & objectives: Parathyroid carcinoma is a rare endocrine neoplasm with a poor prognosis. Two cases are presented in young patients who debuted with elevated hypercalcemia. Methods: Calcemia showed values of 17.8 and 18.2 mg/dL (normal: 8.5-10.5 mg/dL). Cervical ultrasound showed a 4 cm cervical mass in one of the cases. In the other case, an increase in metabolic activity in the thyroid gland was identified on scintigraphy. Parathyroidectomy was performed in the first case and total thyroidectomy with cervical dissection in the second case. Results: Histopathological findings showed in the first case the absence of a true capsule, variable cellularity, and broad bands of fibrous connective tissue extending from the peritumoral pseudo- capsule; vascular invasion was also observed. In the second case, the thyroid gland was infiltrated by cell proliferation with little cell atypia, but with vascular invasion, involvement of the external thyroid capsule, and the presence of fibrous trabeculation. Both patients have a parafibromin mutation and had lymph node metastases at diagnosis. Currently, patients are asymptomatic and closely monitored. Conclusion: Histopathologic findings rather than biochemical or clini- cal features predict outcome. Early and en bloc surgery, including cen- tral lymph node dissection, should be the minimal surgical approach in any patient with suspected parathyroid cancer. E-PS-09-012 Uncommon thyroid pathology encountered in a surgical pathology review of 3,427 consecutive adult thyroid lesions R. Kanthan*, R. Sabaratnam *University of Saskatchewan, Canada Background & objectives: Benign and neoplastic thyroid lesions are commonly encountered in general surgical pathology practice. The aim of this study is to raise clinical awareness of uncommon neoplastic and nonneoplastic pathological lesions of the thyroid. Methods: Diagnosis of two unusual thyroid lesions: sclerosing mucoepidermoid carcinoma and solitary fibrous tumour prompted a 25-year review of surgical pathology cases with “thyroid” in the final diagnosis. Exclusion criteria included fine needle aspiration biopsies, and all thyroid tissue outside the thyroid gland. All cases were reviewed and categorized by age, sex and pathological diagnosis with in-depth review of uncommon lesions. Results: 3,427 adult thyroid lesions were reviewed. They commonly occurred among 40-60 years with female predominance-2714 cases. 1896 cases~55% were benign non-neoplastic lesions with thyroidi- tis-352 cases~10% and Grave’s disease-230 cases~7%. Neoplastic lesions accounted for 1531 cases~45% with the majority being malignant lesions-1053 cases~31%. Benign neoplastic lesions were predominantly follicular adenoma -474 cases~14%. Papillary carci- noma was the commonest malignancy-882 cases~26%, with follicu- lar carcinoma-83 cases~2.4%, anaplastic carcinoma-17 cases~0.5%, medullary carcinoma-18 cases~0.53%, poorly differentiated thyroid carcinoma-7 cases~0.2% and malignant lymphomas-39 cases~1.14% Uncommon benign lesions included hyalinizing trabecular tumour, intrathyroidal ectopic thymus, and lymphoepithelial cyst with solid cell nests. Uncommon malignant lesions included mucoepidermoid carcinoma with/without eosinophilia, metastatic renal cell carcinoma and solitary fibrous tumour. Conclusion: Thyroid lesions requiring surgical excision in adults occur more frequently in women. They are more likely (70%) to be benign, than malignant-30%. Papillary carcinoma is the commonest epithelial malignancy followed by follicular, malignant lymphomas, medullary, anaplastic and poorly differentiated carcinomas. Increased clinical awareness with recognition of uncommon lesions both benign and malignant as seen in this case series review is important for accu- rate pathological diagnosis and thus appropriate patient management. E-PS-09-013 EBV-positive diffuse large B-cell lymphoma of the thyroid, suggest- ing aberrant CD3 expression T. Kawasaki*, K. Kanemoto, H. Inoue, T. Yamazaki, M. Nakahira, Y. Ebihara, M. Kohri, K. Tsukasaki, N. Takahashi, Y. Sonoda, J. Ichikawa, K. Gotoda, M. Doi, H. Masaoka, A. Sasaki *Department of Pathology, Saitama Medical University International Medical Center, Japan Background & objectives: Herein, we report an exceptionally rare case with Epstein-Barr virus (EBV)- as well as aberrant CD3-positive diffuse large B-cell lymphoma (DLBCL) involving the thyroid. Methods: The patient, a 72-year-old man, presented with a chief com- plaint of a neck mass that had grown rapidly in the prior three months. Anaplastic thyroid carcinoma (ATC) was clinically suspected. Fine-nee- dle aspiration cytology of the thyroid lesion was performed three times, with the initial two attempts being nondiagnostic or unsatisfactory, while the third was suspicious for malignancy, favouring carcinoma. Results: He underwent total thyroidectomy with lymph node dissec- tion. Macroscopically, the thyroid tumour, measuring 89x65x39 mm, located mainly in the right lobe, was whitish, relatively well-defined and solid, accompanied by geographic necroses. Histologically, large atypical lymphoid cells showing Hodgkin/Reed-Sternberg (HRS)- like, multinuclear and/or pleomorphic forms proliferated in clusters or sporadically, with infiltration of numerous small lymphocytes and macrophages. These atypical cells extended to the anterior neck mus- cles as well as one of the parathyroid glands. Tumour involvement