Ancillary techniques on the evaluation of canine cutaneous mast cell tumors from Brazil

Abstract

The use of histologic classification by a 2-tier grading system only, immunohistochemistry (IHC) for KIT and Ki-67 and polymerase chain reaction (PCR) for internal tandem duplications (ITD) on exon 11 has improved the prognostication of canine cutaneous mast cell tumors (CCMTs) particularly in the United RESUMO O uso de classificação histológica por um novo sistema de graduação que utiliza apenas duas categorias, imuno-histoquímica (IHQ) para KIT e Ki-67 e reação de polimerase em cadeia (PCR) para mutações (duplicações internas) no éxon 11 tem melhorado a avaliação do prognóstico de mastocitomas cutâneos caninos (MCCs), particularmente nos Estados Unidos. No entanto, essas técnicas são ainda pouco utilizadas em laboratórios brasileiros e, até então, nenhum estudo investigou a prevalência de duplicações internas (DIs) em MCCs do país. Este estudo testou o novo sistema de graduação histológica de duas categorias, a imuno-histoquímica para KIT

Use of different fixation times and application of two immunohistochemical methods for detection of KIT and Ki67 proteins in canine cutaneous mast cell tumors

“…Pattern III immunostaining was not observed in the present study. The vast majority of low grade neoplasms presented immunostaining pattern II, corroborating with the literature (Webster et al 2007, Fonseca-Alves et al 2015, Flores et al 2016, Sledge et al 2016. This information is important considering that it has been observed that MCTs that lose membrane expression and acquire cytoplasmic expression for KIT antigen, present a more aggressive biological behavior (Kiupel et al 2004).…”

“…That was the motivation for our prospective study, which sought to assess whether fixation time could be influencing the results of our retrospective study. Flores et al (2016), using other samples from the same laboratory (LPV-UFSM), observed positive immunostaining for Ki67 protein in approximately 70% of the samples analyzed. The difference in the percentage of immunostaining between this study and that by Flores et al (2016), even with different samples, could be associated with the systems of amplification (using a specific polymer for tissues of dogs and cats) and antigen retrieval (under controlled conditions of temperature and pressure) they used for Ki67 protein.…”

“…Counterstain was performed with Harris hematoxylin. Cases of MCT previously submitted to IHC for KIT protein by Flores et al (2016) were used as positive controls. A section of the analyzed tissue incubated only with the antibody diluent (phosphate buffered saline with Tween ® 20-Sigma -PBST) was used as negative control of each case.…”

“…In parallel, immunohistochemistry (IHC) and polymerase chain reaction (PCR) have been used to assist with determining the prognosis of MCTs (Kiupel et al 2004, Webster et al 2006, Kandefer-Gola et al 2015. Using IHC, especially with antibodies that detect KIT (tyrosine kinase membrane receptor) and Ki67 (marker of cell proliferation) proteins, it is possible to identify the tumors that are most likely to be biologically more aggressive (Webster et al 2007, Strefezzi et al 2010, Flores et al 2016, Sledge et al 2016. PCR has been used in the search for mutations in the c-KIT gene, which present prognostic value and influence the therapeutic approach to each patient (Webster et al 2006, Kiupel 2017.…”