Keratin Expression in Endocrine Organs and their Neoplasms

Abstract

Keratins are intermediate filaments that provide mechanical support and fulfill a variety of additional functions in epithelial cells. Keratins show outstanding degree of molecular diversity. In humans, 54 functional keratin genes exist. Twenty common types of keratins are expressed in highly specific patterns related to epithelial type and stage of cellular differentiation. In general, keratins are classified as high-molecular-weight keratins (expressed in normal stratified epithelium and tumors derived from it) and low-molecular-weight keratins (expressed in normal simple epithelium and tumors derived from it). Histologically, endocrine organs belong to simple epithelium; thus, endocrine tissues usually express low-molecular-weight keratins. When an endocrine organ undergoes malignant transformation, its keratin profile usually remains constant. However, keratin expression in endocrine organs and endocrine tumors is much more complicated because of their diversified histogenesis. In this review article, we will first briefly review the molecular biology and protein chemistry of the keratins. We will then review the expression patterns of keratins in normal endocrine tissue and endocrine neoplasms.

Endocrine tumours of the pancreas

“…Production of serotonin is highly uncommon in PETs and indicates a primary in the tubular digestive tract, in particular in the small intestine. It is important to note that the cytokeratin profile (CK7, CK20) is of no value in this respect, hence no tissue should be wasted on these markers 47–49 . Thyroid transcription factor‐1 (TTF‐1) expression points at well‐differentiated endocrine tumours of the lung; however, only 35–53% of these show immunopositivity 50,51 .…”

“…It is important to note that the cytokeratin profile (CK7, CK20) is of no value in this respect, hence no tissue should be wasted on these markers. [47][48][49] Thyroid transcription factor-1 (TTF-1) expression points at well-differentiated endocrine tumours of the lung; however, only 35-53% of these show immunopositivity. 50,51 TTF-1 cannot be used for identification of the primary tumour site of poorly differentiated endocrine carcinomas, because 50% of these in extrapulmonary location are positive.…”

A Strong Neutrophil Elastase Proteolytic Fingerprint Marks the Carcinoma Tumor Proteome

“…ments of cytokeratins are among the most frequently tested protein-based cancer markers. Cytokeratin typing and quantitation for cancer studies, as well as diagnosis, prognosis, and therapy monitoring, have become routine in recent years (2)(3)(4)(5)(6). Moreover, keratins are cleaved in a cancer-dependent manner, and some of the keratin-based antibodies used in the context of cancer recognize such fragments (7).…”

Serum cytochrome c and m30‐neoepitope of cytokeratin‐18 in chronic hepatitis C

“…Cytokeratin 18 (CK18) is an intermediate filament of the cytoskeletal architecture, representing about 5% of total protein in simple epithelia and parenchymal cells, most prominently expressed in hepatocytes . Induction of apoptosis results in early cleavage of CK18 by caspases 3, 6, 7 and 9.…”