Insulinoma-associated protein 1 (INSM-1) expression in medullary thyroid carcinoma FNA: a multi-institutional study

Zahra Maleki, Mikk Abram, Marco Dell'Aquila, Irem Kilic, Ryan Lu, Teresa Musarra, Guliz Barkan, Erja Rajakorpi, Esther Diana Rossi, Ivana Kholová

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Introduction: Insulinoma-associated protein 1 (INSM-1) is expressed in both normal tissues and neoplasms with neuroendocrine differentiation such as small cell lung carcinoma and pancreatic neuroendocrine tumors. The aim of this study was to evaluate the INSM-1 expression in medullary thyroid carcinoma (MTC) in the aspirated material and its preoperative diagnostic value. Materials and methods: MTC cases with available cytological material from 5 institutions were retrospectively identified. INSM-1 expression was analyzed in 48 cell blocks prepared from fine-needle aspiration samples from histologically confirmed cases of MTC. Twenty-nine samples were aspirates from primary thyroid lesions and 19 from secondary lesions lymph node or liver lesions. INSM-1 immunostain was done using the Ventana Automatic System (Ventana Medical Systems, Tucson, AZ). The control group consisted of 20 samples from histologically confirmed cases of papillary, follicular, and anaplastic thyroid carcinomas and secondary thyroid malignancies (squamous cell carcinoma, malignant melanoma). Results: The male to female (M:F) ratio in MTC group was 1:1.5 and the average age was 55.6 years (range: 24-84 years). INSM-1 nuclear staining in at least 5% of cells was considered positive. Forty-five (93.75%) MTC samples were positive including all primary tumor aspirates. All control samples were negative. Conclusions: INSM-1 nuclear positivity is a reliable marker of MTC neuroendocrine differentiation on cytology material from both primary tumor and metastases. INSM-1 can also discriminate MTC from other primary and secondary thyroid carcinomas when there are cytomorphologic overlaps.

Original languageEnglish (US)
Pages (from-to)185-190
Number of pages6
JournalJournal of the American Society of Cytopathology
Issue number3
StatePublished - May 1 2020


  • FNA
  • Fine-needle aspiration
  • INSM-1
  • Immunohistochemistry
  • Insulinoma-associated protein 1
  • Medullary thyroid carcinoma
  • Thyroid

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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