The spectrum of melanocytic lesions: From examples to biologically relevant conditions

The progression of melanocytic lesions and the prediction of their behavior depends on a careful assessment of essential pathological features like symmetry and maturation (both morphological and functional). Both the tumorigenic and mitogenic activity are also paramount in the prediction of metastatic potential and represent the essential elements to define the growth phase of melanocytic lesions and the transition and classes used to categorize them. All these elements are interconnected and closely related with the molecular pathways and groups for both junctional and dermal compartments. All these aspects are discussed from typical cases, along with the main differential diagnosis

Pathological Bases for a Robust Application of Cancer Molecular Classification

<p>Any robust classification system depends on its purpose and must refer to accepted standards, its strength relying on predictive values and a careful consideration of known factors that can affect its reliability. In this context, a molecular classification of human cancer must refer to the current gold standard (histological classification) and try to improve it with key prognosticators for metastatic potential, staging and grading. Although organ-specific examples have been published based on proteomics, transcriptomics and genomics evaluations, the most popular approach uses gene expression analysis as a direct correlate of cellular differentiation, which represents the key feature of the histological classification. RNA is a labile molecule that varies significantly according with the preservation protocol, its transcription reflect the adaptation of the tumor cells to the microenvironment, it can be passed through mechanisms of intercellular transference of genetic information (exosomes), and it is exposed to epigenetic modifications. More robust classifications should be based on stable molecules, at the genetic level represented by DNA to improve reliability, and its analysis must deal with the concept of intratumoral heterogeneity, which is at the origin of tumor progression and is the byproduct of the selection process during the clonal expansion and progression of neoplasms. The simultaneous analysis of multiple DNA targets and next generation sequencing offer the best practical approach for an analytical genomic classification of tumors.<br>Pathological Bases for a Robust Application of Cancer Molecular Classification. Available from: https://www.researchgate.net/publication/275039181_Pathological_Bases_for_a_Robust_Application_of_Cancer_Molecular_Classification [accessed Apr 17, 2015].</p

Molecular mechanisms in melanoma

<p> </p> <div> <div> <div> <p>The review of melanoma by Mil- ler and Mihm (July 6 issue)1 clearly characterizes the linear progression of melanocytic lesions, from the morphologic perspective to the molecular per- spective.2,3 However, the genetic alterations would have more relevance if they result in kinetic ad- vantage and progression. My colleagues and I have studied a series of dysplastic nevi (92 low-grade and 31 high-grade lesions) and melanomas in situ (15 lesions) using proliferation (Ki-67 labeling), apoptosis (in situ end labeling), and cell-cycle reg- ulators (RB1, TP53, p21WAF1, and p27Kip1).4 Our analysis highlighted a clear topographic hetero- geneity at the early stage of melanocytic trans- formation: slow kinetics in the dermal compart- ment of low-grade melanocytic dysplasia and a higher incidence of TP53 alterations in high-grade melanocytic dysplasia than in low-grade dyspla- sia and melanomas. These findings suggest that melanocytic dysplasia is a marker of the risk of melanoma rather than a direct precursor. </p> </div> </div> </div> <p> </p

Morphological and biological features of neoplasms: Integration of molecular findings

<p>Integration of morphologic and molecular findings in neoplasms (for details, please refer to Histopathology 2008; 53(1):1-19).</p> <p>Molecular definition of neoplasm and precursor lesions. Intraepithelial lesions and topographic heterogeneity.</p> <p>Biological bases of neoplasm natural history.</p> <p>- Clonality and loss of heterozygosity (LOH) in neoplasms. Fractional allelic loss.</p> <p>- Genetic control of initiation and promotion. Tumor progression.</p> <p>- Topographic heterogeneity and tumor cell segregation. Accumulation of genetic alterations.</p> <p>- Molecular pathways pleiotropism and redundancy.</p

Sentinel node in malignant melanoma – The pathologist’s point of view

<p>Overall, the benefit of accurate nodal staging obtained by SLN biopsy far outweighs the risks and has important implications for patient management. That is not to say that this test should be over-utilized. SLN biopsy is an extremely valuable tool to stratify a group of patients in which the standard prognostic factors have failed providing reliable information. Although SLN biopsy can still be considered a relatively “new” diagnostic tool, clear prognostic and therapeutic implications can be drawn when the samples are properly handle. The mRNA detection of melanoma-associated antigens (tyrosinase, MART-1, gp100, and others) remains experimental unless conclusive results on its clinical value are available. Finally, there are four major reasons to perform SLN biopsy. (1) SLN biopsy improves the accuracy of staging and provides valuable prognostic information. The “N classification” distinguishes between macroscopic and microscopic metastases. (2) SLN biopsy facilitates early therapeutic lymph node dissection for those patients with nodal metastases. (3) SLN biopsy identifies patients who are candidates for adjuvant therapy with interferon α-2b. (4) SLN biopsy identifies homogeneous patient populations for entry onto clinical trials of novel adjuvant therapy agents.</p

Pathology of fore and midgut neuroendocrine tumours

<p>There is much confusion in both definition and practical issues among pathologists and clinicians alike for neuroendocrine tumours/carcinomas (NETs/NECs). This review focuses the attention on key issues of foregut and midgut NET: pathological features (nomenclature, classification, diagnostic criteria, grading, staging, markers and prognosis), molecular genetics, and how to approach common problems in NET (multifocal vs multicentric, metastatic potential and prediction of primary site). The value of the term neuroendocrine is related to its connotation of a particular phenotype or differentiation pattern. Accordingly, the NET nomenclature can be addressed by using any of the following groups of terms: (1) well-differentiated NET, well-differentiated NEC, or poorly differentiated NEC; or (2) NECs (grades IeIII), indicating in an explanatory note the equivalent terminology, when appropriate. Ultimately, the use of specific NET terms remains a personal preference, but what is the most critical is the necessity that the terms will be understood by health professionals caring for patients and that the terms can be grouped and translated for epidemiologic and molecular studies that can offer unique targets for specific therapies.</p

Re: Pomerance et al. High-level expression, activation, and subcellular localization of p38-MAP kinase in thyroid neoplasms. J Pathol 2006; 209: 298-306

<p> </p> <div> <div> <div> <p>The neoplastic transformation of follicular thyroid cells essentially transmits signals to the mitogen- activated protein kinase (MAPK) pathways [1 – 3], which result in the activation of signal transduction cascades (JNK1, ERKs, and p38 kinases) [4,5]. The cascade end points include the MAPK-activated pro- tein kinases and some of the numerous transcrip- tion factors that regulate apoptosis, inflammation, cell growth, and differentiation. The role of p38-MAPK has been recently emphasized in cell line studies from follicular thyroid neoplasms [3,6]. </p> <div> <div> <div> <p>Our findings confirm the prominent role of p38- MAPKs in inflammation, immune activation, and apoptosis, and provide additional support to those recently reported [3,6]. It is also worth remembering that the activation mechanisms would include phos- phorylation and protein accumulation due to a deficient degradation system (down-regulation of ubiquityla- tion) [8]. </p> </div> </div> </div> </div> </div> </div> <p> </p

Kinetic topographical heterogeneity in follicular thyroid neoplasms and growth patterns

<p>I have topographically analysed the kinetic features [proliferation by Ki67 index and apoptosis by in situ end labelling (ISEL) or ISEL index] of follicular thyroid neoplasms (43 FTA, 76 FTC—including 28 minimally invasive and 48 widely invasive—and 27 anaplastic carcinomas) and have obtained similar results. Apart from the diagnostic applicability, these results provide insight into the basis of the known architectural patterns of thyroid tumours.</p> <p>The Ki67⁄ ISEL indices provide kinetic advantage in the internal compartments of benign lesions and in the peripheral compartments of malignant lesions. Benign lesions (FTA) and low-grade malignancies (minimally invasive FTC) show higher rates of apoptosis in peripheral compared with internal compartments, whereas high-grade malignancies (widely invasive FTC and anaplastic thyroid carcinoma) reveal the inverse relationship.</p> <p>Conclusion: Differential cell kinetics in follicular thyroid neoplasms contributes to a topographical segregation of tumour cells and the growth pattern (encapsulation and invasiveness at the tumour periphery).</p

Molecular markers for colon cancer – from bench to bedside: Molecular subclassification

<p>Overview<br>- Limitations of adenoma-carcinoma sequence as genetic model for colorectal tumorigenesis<br>- Genetic instability and DNA methylation as main features for molecular classification<br>- Colo-rectal carcinoma molecular classification<br>* Clinical features<br>* Pathological-molecular correlation<br>Molecular classification of colo-rectal carcinomas is mainly based on:<br>- Main pathways: Adenomatous (APC ± KRAS, hypo-CH3) and serrated (BRAF, CIMP-high)<br>- Microsatellite profiles further subclassify each group.<br>- CIMP-low represents a new epigenomic subtype (KRAS)</p

Microsatellite Instability and Mistmatch Repair protein analysis

<p>Microsatellite Instability Testing in CRC and Interpretation</p> <p>Microsatellite instability is a type of mutation that occurs in microsatellite regions (short polymorphic DNA segments) by nucleotide addition (increased size) or nucleotide loss (decreased size) in the repeats. These changes in size of the microsatellite repeat are known as microsatellite instability. Microsatellite instability occurs because of deficient/loss of DNA mismatch repair (MMR), which requires the function of several DNA mismatch repair proteins (hMLH1, hMSH2, hMSH6, hPMS2, hMSH3 and hMLH3). Loss of expression of these proteins in tumors can be detected by IHC performed on paraffin sections.</p> <p>Approximately 15% sporadic colorectal cancers and other sporadic adenocarcinomas of the spectrum of HNPCC cancers can have MSI-positive status. Therefore, confirmation of HNPCC (hereditary non-polyposis colorectal cancer) requires identification of germline mutations (detected in peripheral blood DNA) in one of the DNA mismatch repair genes, whereas somatic hypermethylation of the hMLH1 promoter leading to loss of hMLH1 expression is the underlying abnormality causing MSI in sporadic tumor tissues.</p> <p>For the MSI test DNA is extracted from unstained sections from formalin fixed and paraffin embedded tissue specimens. PCR amplification is performed with sets of primers that amplify five microsatellite markers (BAT25, BAT26, D2S123, D5S346 and D17S250), classifying the tumors as: 1) MSI-High level (MSI-H, >30% markers positive for MSI); 2) MSI-Low (MSI-L, <30% markers positive for MSI); 3) Microsatellite stable (MSS, no marker shows MSI).</p> <p>If a tumor is MSI-H the patient might have HNPCC, and it is important that the MSI test report states that there are potential genetic implications of the test results and genetic counseling should be recommended. If HNPCC is ruled out, MSI-H identifies a sub-group of sporadic adenocarcinomas that have distinct clinical pathological features namely better survival and resistance to 5-fluorouracil (5FU). If no loss of expression of hMSH2 or hMLH1 is seen in MSI-H tumors by IHC or if the tumor is MSI-L or MSS but there is clinical suspicion of HNPCC, evaluation of other MMR genes, in particular hMSH6 and hPMS2 may be performed, by immunohistochemical stains and/or germline mutational analyses.</p> <p>Correlation of MSI Test Results and DNA Mismatch Repair Protein IHC</p> <p>Note that when hMLH1 expression is lost hPMS2 is also lost because hPMS2 requires hMLH1 for stability through heterodimerization; in contrast, if hPMS2 is lost hMLH1 expression is preserved because hMLH1 also forms heterodimers with other proteins, thus being protected from degradation. Similarly, when hMSH2 expression is lost, hMSH6 is also lost because hMSH6 requires hMSH2 for stabilization through heterodimerization; in contrast, if hMSH6 is lost hMSH2 expression is preserved because hMSH2 also forms heterodimers and is stabilized by other proteins.</p> <p>Clinical Indications for Microsatellite Instability Testing in Colorectal Cancer</p> <p>The most recent guidelines to help decide whether a patient should undergo molecular testing to rule out HNPCC (revised Bethesda criteria). The pathologist can easily identify patients with criteria 1 and 2 (tumors before the age of 50, or synchronic-metachronic tumors in specific locations), and criterium 3 specifically depends on the identification by the pathologist of tumors that demonstrate MSI-suggestive histology (Tumor infiltrating lymphocytes, Crohn’s-like lymphocytic reaction, mucinous or signet-ring cell differentiation, poorly differentiated carcinomas with medullary growth pattern).</p> <p>MSI and Prediction of Tumor Prognosis, Progression and Chemotherapy Response</p> <p>Several studies have reported unique clinicopathological features of tumors related to their MSI status, namely a relationship with response to chemotherapy (5-FU) and an improved prognosis in tumors that are MSI-H.</p> <p>Studies have shown that MSI-H colorectal cancers show less lymph node metastases burden and have better survival, independent of stage, site, tumor grade, and age. MSI and MMR downregulation also play a role in tumor progression is bladder and adrenal medullary neoplasms. Chemotherapy of stage II and III CRC with 5-fluorouracil did not improve survival if the tumor was MSI-High. In contrast, patients with microsatellite stable tumors treated with 5-FU had better survival compared with patients who were not treated.</p