title: A Case of Primary Mammary Analog Secretory Carcinoma (MASC) of the Thyroid Masquerading as Papillary Thyroid Carcinoma: Potentially More than a One Off.
abstract: We present the second reported mammary analog secretory carcinoma (MASC) apparently arising in the thyroid and propose a potential close relationship to ETV6-NTRK3 fusion papillary thyroid carcinoma. The patient, a 36 year old woman, presented with a neck mass of 1 year's duration. Imaging studies showed a tumor involving most of the thyroid with enlarged regional lymph nodes. FNA biopsy yielded a diagnosis of "papillary thyroid carcinoma". Resection revealed a 4.5 cm infiltrative tumor. Final diagnosis was "papillary thyroid carcinoma (PTC) consistent with diffuse sclerosing variant" with positive lymph nodes (2+/4) and margins. Histologic features included mixed microcystic, solid, follicular and papillary architecture, prominent nucleoli, abundant nuclear grooves and rare nuclear pseudo-inclusions. Despite radioactive iodine, radiotherapy and multiagent chemotherapy, the patient progressed over 6 years with local recurrence and additional lymph node involvement finally developing widespread distant metastases. Prompted by the breast carcinoma-like histopathology of a metastasis, immunohistochemical staining was performed and revealed strong expression of GATA3 and mammaglobin with no reactivity for thyroglobulin or TTF-1. The original tumor was then tested and showed the same immunoprofile. RT-PCR confirmed the presence of an ETV6-NTRK3 fusion consistent with a diagnosis of MASC. Our patient's clinical, imaging and morphologic features remarkably mimicked papillary thyroid carcinoma. At the molecular level, the ETV6-NTRK3 fusion in this patient involved exons reported in the rare "papillary thyroid carcinoma" with this translocation. Given the immunophenotype of this case, it is possible that at least some ETV6-NTRK3 fusion positive PTC are actually MASC masquerading as papillary thyroid carcinoma.
authors.affiliation: Department of Pathology, University of New Mexico School of Medicine (UNM SOM), MSC08-4640, Albuquerque, NM, 87131-0001, USA.
authors.forename: S
authors.initials: S
authors.lastname: Reynolds
authors.affiliation: Division of Hematology/Oncology, Department of Internal Medicine, University of New Mexico School of Medicine (UNM SOM), Albuquerque, NM, USA.
authors.forename: M
authors.initials: M
authors.lastname: Shaheen
authors.affiliation: Division of Otolaryngology, Department of Surgery, University of New Mexico School of Medicine (UNM SOM), Albuquerque, NM, USA.
authors.forename: G
authors.initials: G
authors.lastname: Olson
authors.affiliation: Department of Pathology, University of New Mexico School of Medicine (UNM SOM), MSC08-4640, Albuquerque, NM, 87131-0001, USA.
authors.forename: M
authors.initials: M
authors.lastname: Barry
authors.affiliation: Department of Pathology, University of New Mexico School of Medicine (UNM SOM), MSC08-4640, Albuquerque, NM, 87131-0001, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Pathology, University of New Mexico School of Medicine (UNM SOM), MSC08-4640, Albuquerque, NM, 87131-0001, USA. tbocklage@salud.unm.edu.
authors.forename: T
authors.initials: T
authors.lastname: Bocklage
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis; D044963:Biopsy, Fine-Needle; D002277:Carcinoma / Q000175:diagnosis* / Q000235:genetics; D002291:Carcinoma, Papillary; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D000069295:Mammary Analogue Secretory Carcinoma / Q000175:diagnosis* / Q000235:genetics; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000235:genetics; D020812:Receptor, trkC; D000097764:ETS Translocation Variant 6 Protein
chemical_list: D014408:Biomarkers, Tumor; D015514:Oncogene Proteins, Fusion; C484319:ETV6-NTRK3 fusion protein, human; D020812:Receptor, trkC; D000097764:ETS Translocation Variant 6 Protein
keywords: ETV6-NTRK3 fusion; Genetics; MASC; Papillary thyroid carcinoma; Thyroid carcinoma