Stains & CD markers

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Lisa Rooper, M.D.

Last author update: 1 June 2018
Last staff update: 8 August 2023

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PubMed Search: INSM1[TIAB]

Lisa Rooper, M.D.
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Cite this page: Rooper LM INSM1. website. Accessed July 13th, 2024.
Definition / general
  • Insulinoma associated protein 1
  • Previously abbreviated as IA1
Essential features
  • Nuclear marker of neuroendocrine differentiation with equivalent or better sensitivity and specificity compared to synaptophysin, chromogranin and CD56
  • Expressed in a broad spectrum of neuroendocrine tumors (including small cell carcinoma, large cell neuroendocrine carcinoma and well differentiated neuroendocrine tumor / carcinoid tumor of various sites, paraganglioma / pheochromocytoma, Merkel cell carcinoma, olfactory neuroblastoma and medullary thyroid carcinoma)
  • Also expressed in normal adult neuroendocrine tissues (adrenal medulla, pineal gland, pituitary gland, gastrointestinal enterochromaffin cells, pancreatic islet cells, thyroid C cells) and developing neurons
Clinical features
Uses by pathologists
Prognostic factors
  • High expression of INSM1 is associated with increased progression free survival and chemosensitivity in small cell lung carcinoma (Oncotarget 2017;8:73745)
  • Higher expression in midgut gastrointestinal neuroendocrine carcinomas with metastases compared to those not yet metastasized (Am J Clin Pathol 2015;144:579)
  • Nuclear stain
Microscopic (histologic) images

Contributed by Lisa M. Rooper, M.D.
Small cell carcinoma (lung).

Small cell carcinoma (lung)

Large cell neuroendocrine carcinoma (lung).

Large cell neuroendocrine carcinoma (lung)

Atypical carcinoid tumor (lung).

Atypical carcinoid tumor (lung)

Olfactory neuroblastoma.

Olfactory neuroblastoma

Pituitary adenoma.

Pituitary adenoma

Pancreatic neuroendocrine tumor.

Pancreatic neuroendocrine tumor

Paraganglioma (carotid body).

Paraganglioma (carotid body)

Middle ear adenoma.

Middle ear adenoma

Thyroid C cell hyperplasia.

Thyroid C cell hyperplasia

Positive staining - normal
Positive staining - tumors
Negative staining - normal
Negative staining - tumors
  • Adrenal gland: adrenal cortical adenoma (0%) (Am J Clin Pathol 2015;144:579)
  • Brain: ganglioglioma (7%), ependymoma (5%), pilocytic astrocytoma (0%) (J Neuropathol Exp Neurol 2018;77:374)
  • Gastrointestinal tract: colonic adenocarcinoma (0%) (Am J Clin Pathol 2015;144:579)
  • Head and neck: squamous cell carcinoma (2%), mucoepidermoid carcinoma (3%), adenoid cystic carcinoma (0%), polymorphous adenocarcinoma (0%), secretory carcinoma (0%), pleomorphic adenoma (0%), HPV related multiphenotypic carcinoma (0%), NUT carcinoma (0%), sinonasal undifferentiated carcinoma (0%), mucosal melanoma (0%) (Am J Surg Pathol 2018;42:665)
  • Hematolymphoid: small lymphocytic lymphoma (0%) (J Cutan Pathol 2018;45:129)
  • Lung: adenocarcinoma (3%), squamous cell carcinoma (4%) (Am J Surg Pathol 2017;41:1561)
  • Pancreas: ductal adenocarcinoma (0%), acinar cell carcinoma (0%), solid pseudopapillary neoplasm (0%) (Med Mol Morphol 2018;51:32)
  • Prostate: adenocarcinoma (9%) (Lab Invest 2017;97:262A)
  • Skin: melanoma (0%) (Am J Clin Pathol 2015;144:579)
  • Soft tissue: chondrosarcoma (0%), chordoma (10%), myxofibrosarcoma (0%), myxoid liposarcoma (0%), intramuscular mxyoma (0%), low grade fibromyxoid sarcoma (0%), myoepithelioma (5%), angiomatoid fibrous histiocytoma (0%), dedifferentiated liposarcoma (0%), CIC rearranged sarcoma (0%), synovial sarcoma (0%) (Mod Pathol 2018;31:744)
  • Thyroid / parathyroid: papillary carcinoma (0%), follicular carcinoma (0%), follicular adenoma (0%), parathyroid carcinoma (0%), parathyroid adenoma (0%) (Am J Surg Pathol 2018;42:665)
Board review style question #1
Which of the following tumors should be negative for INSM1?

  1. Extraskeletal myxoid chondrosarcoma
  2. Middle ear adenoma
  3. Parathyroid adenoma
  4. Small cell carcinoma of the uterine cervix
  5. Well differentiated pancreatic neuroendocrine tumor, grade 1
Board review style answer #1
C. Parathyroid adenoma. Although parathyroid neoplasms frequently stain with the common neuroendocrine stain chromogranin, they are consistently negative for INSM1.

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Reference: INSM1
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