Insulinoma-associated protein 1 immunostaining on cytology specimens: an institutional experience.

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Insulinoma-associated protein 1 immunostaining on cytology specimens: an institutional experience.

Hum Pathol. 2018 Nov 28;:

Authors: Rodriguez EF, Judd Fite J, Chowsilpa S, Maleki Z

Abstract
Neuroendocrine tumors (NET) are epithelial neoplasms with prominent neuroendocrine differentiation. Cytologic examination and utilization of immunohistochemical (IHC) markers are important diagnostic tools for the evaluation of these tumors. Herein we report our experience with the application of INSM1 in cytology samples. We searched our pathology system for cytological specimens with INSM1 IHC performed from 2017-2018. Patients' demographics were recorded, and cytology materials were reviewed including all neuroendocrine IHC markers performed. A total of 134 (67M, 67F) specimens with INSM1 immunohistochemistry were identified. Specimens included 91 (68.2%) neuroendocrine tumors (NET) or tumors with neuroendocrine features (TNEF), 33 (24.3%) non-neuroendocrine lesions (non-NET) and 10 (7.5%) non-neoplastic diagnoses. INSM1 was positive in 90 (99%) of the NET/TNEF and negative in 32 (97%) non-NET. CD56 was positive in 42 (95.5%) of the NET/TNEF and negative on 9 (69.2%) of the non-NET. The sensitivity of INSM1 was 99% and specificity was 97%, while the sensitivity of CD56 was 95.5% and specificity was 69.2%. Chromogranin had the lowest sensitivity (82.5%) and synaptophysin had the lowest specificity (66.7%). Both positive and negative predictive values of INSM1 were higher than CD56 (99% versus 91.3% and 97% versus 81.8%, respectively). INSM1 is a sensitive and specific marker for detection of neuroendocrine tumors in cytology samples independent of primary site.

PMID: 30502379 [PubMed - as supplied by publisher]

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