Evaluation of human epidermal growth factor receptor 2 expression in colorectal cancer and its correlation with clinicopathological variables

Sana Ahuja; Vinod Kumar Arora

doi:10.4103/jmgims.jmgims_20_21

ORIGINAL ARTICLE

Year : 2021 | Volume : 26 | Issue : 2 | Page : 103-107

Evaluation of human epidermal growth factor receptor 2 expression in colorectal cancer and its correlation with clinicopathological variables

Sana Ahuja, Vinod Kumar Arora
Department of Pathology, University College of Medical Sciences, New Delhi, India

Date of Submission	25-Feb-2021
Date of Acceptance	05-Oct-2021
Date of Web Publication	10-Feb-2022

Correspondence Address:
Dr. Sana Ahuja
Department of Pathology, University College of Medical Sciences, New Delhi
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jmgims.jmgims_20_21

Abstract

Context: Colorectal cancer is the third most common cancer in men and the second most common cancer in women worldwide. Overexpression of human epidermal growth factor receptor 2 (HER2) in breast and gastric cancer is associated with poor prognosis. However, in colorectal cancer, there are no specific guidelines for immunohistochemical interpretation of HER2. Furthermore, there are conflicting reports regarding correlation of clinicopathological parameters with HER2 expression. Aim: The present study was conducted to determine the frequency of HER2 expression in colorectal cancer and its correlation with clinicopathological variables, if any. Methods: Resection specimens for colorectal cancer over a 2-year period were included in this retrospective study. HER2 immunostaining was done using a monoclonal antibody followed by evaluation of pattern and intensity of staining along with correlation of cells with membranous positivity. Clinicopathological parameters such as age, gender, tumor location, histological subtype of tumor along with tumor stage and grade were analyzed using Fisher's exact test for significance. Results: Of the 50 cases analyzed, 70%, 28%, and 2% were conventional, mucinous, and signet cell ring adenocarcinomas, respectively. The majority were moderately differentiated (56%) and most of the cases presented at Stage III. Weak-to-moderate cytoplasmic positivity was seen in 18% cases, while one case each (2%) showed combined cytoplasmic-membranous and complete membranous positivity, respectively. No significant correlation could be established between HER2 immunostaining and histological subtype or tumor stage/grade. Conclusions: Colorectal cancer demonstrates a very low membranous positivity to HER2 immunostaining. HER2 expression in colorectal cancer has no correlation with clinicopathological variables such as tumor grade, stage, and histological subtype. HER2 does not appear to have any prognostic role to play in colorectal cancer in the context of Indian population.

Keywords: Colorectal cancer, grade, human epidermal growth factor receptor 2, stage

How to cite this article:
Ahuja S, Arora VK. Evaluation of human epidermal growth factor receptor 2 expression in colorectal cancer and its correlation with clinicopathological variables. J Mahatma Gandhi Inst Med Sci 2021;26:103-7

How to cite this URL:
Ahuja S, Arora VK. Evaluation of human epidermal growth factor receptor 2 expression in colorectal cancer and its correlation with clinicopathological variables. J Mahatma Gandhi Inst Med Sci [serial online] 2021 [cited 2023 Jun 4];26:103-7. Available from: https://www.jmgims.co.in/text.asp?2021/26/2/103/337433

Introduction

Globally, colorectal cancer is the third most common cancer in men and the second most common cause in women accounting for 10% of all cancers. However, it is the second most common cause of cancer-related deaths worldwide in both the genders after lung cancer.^[1] In India, the annual incidence rates (AARs) for colon cancer and rectal cancer in men are 5.36 and 5.17/100,000, respectively. The AAR for colon cancer in women is 4.3/100,000.^[2]

The histological types of colorectal cancer include conventional adenocarcinoma, mucinous adenocarcinoma, signet ring cell carcinoma, medullary, adenosquamous, and small cell carcinoma. By convention, the grading system for colorectal adenocarcinomas is based on the extent of well-formed glands, either well differentiated (>95%), moderately differentiated (50%–95%), or poorly differentiated (<50%).^[3]

Human epidermal growth factor receptor 2 (HER2), a member of epidermal growth factor receptor family, is a transmembrane receptor tyrosine kinase. It is a proto-oncogene located on the long arm of chromosome 17 and plays a key role in cell proliferation, differentiation, inhibition of apoptosis, and tumor progression.^[4] Overexpression/amplification of HER2^[5] is seen in breast and gastric cancers where it is associated with increased risk of disease recurrence and worse prognosis. However, the guidelines for interpretation of immunohistochemistry of HER2 in colorectal cancer are not specific. There is variability in the results reported about the correlation of HER2 with clinicopathological parameters, with some studies^[5],[6],[7] suggesting no correlation, while others^[8],[9] indicating a positive correlation between higher grade and lymph node metastases.

This study was conducted to determine the pattern of HER2 immunohistochemical (IHC) expression in colorectal cancer and to determine if there is any correlation between HER2 expression and clinicopathological parameters.

Methods

The study was a retrospective study conducted over a period of 2 years after clearance from the institutional ethics committee.

Inclusion criteria

Patients of colorectal cancer who underwent resection between January 2017 and December 2018 were included in the study.

Exclusion criteria

Patients who received any neoadjuvant chemotherapy were excluded from the study.

Clinical details along with histopathology slides and paraffin-embedded blocks of all cases were retrieved. Histopathological typing of all cases was done according to the WHO Classification of Colorectal Tumors.^[10]

HER2 immunostaining was performed using monoclonal antibody against HER2 (clone RBT, BSB2036) with DAKO EnVision kit on a minimum of two representative sections from all tumors and evaluated. A known case of HER2 positive breast cancer was run with each batch of slides as a positive control.

The slides were evaluated in terms of the following parameters:

Pattern of positivity: The pattern of staining with HER2 was classified as either membranous, cytoplasmic, or both membranous and cytoplasmic, based on the predominant staining pattern
Percentage of cells showing membranous positivity: The percentage of tumor cells showing membranous pattern of staining with HER2 was noted. The percentage of positive cells was classified into <10% or >10%
Intensity of staining: The staining intensity of the HER2-positive cells was graded as faint, weak to moderate, and strong complete by comparing the intensity of staining on the test cases with the positive control.

The cases with moderate to strong cytoplasmic/ membranous immunostaining in >10% of tumour cells was taken as positive for HER2 while weak cytoplasmic staining in <10% cells was taken as negative. All cases of colorectal cancer were classified based on a two tiered grading system into low grade (well and moderately differentiated) and high grade (poorly differentiated).

Statistical analysis

The data obtained were analyzed using Fisher's exact test for significance. It was applied using Statistical Product and Service Solutions software (SPSS) v. 24.0 and P value was calculated.^[11] P < 0.05 was taken as statistically significant.

Results

A total of 50 patients who underwent resection for colorectal cancer were included in the study. Maximum number of cases (32%) were in the age group 51–60 years with a mean and median age of 51 and 55 years, respectively. Twenty (40%) of cases were women while the remaining (60%) were men.

Conventional adenocarcinomas constituted the major subtype (70%) with remaining being mucinous adenocarcinoma (28%) and signet ring cell adenocarcinoma (2%). Based on tumor location, 30 cases (60%) were confined to the colon while 15 cases (30%) were limited to the rectum. Five (10%) cases involved both colon and rectum. Of the 50 cases, 16 (32%) were well differentiated, 28 were moderately differentiated (56%), and six (12%) cases were poorly differentiated carcinomas [Figure 1]. Most of the patients presented at a late stage with 24 (48%), 20 (40%), and 5 (10%) diagnosed at Stages III, II, and I, respectively. A single case of Stage IV was also present which was managed by surgical debulking. Of the 50 cases, 26 (52%) showed no lymph nodal metastases (N₀), while N₁ (metastases in 1–3 lymph nodes) and N₂ (>4 nodes positive) were seen in 21 (42%) and 3 (6%) cases, respectively.

Figure 1: (a) Low-grade adenocarcinoma (b) High-grade adenocarcinoma (c) Mucinous adenocarcinoma (×200, hematoxylin and eosin)

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Nine (18%) cases showed a weak-to-moderate cytoplasmic staining in more than 10% of tumor cells. Only one (2%) case showed a moderate combined cytoplasmic-membranous staining in >10% of tumor cells while a single case showed complete membranous staining in >10% tumor cells [Figure 2] and [Table 1].

Figure 2: Immunohistochemical expression of human epidermal growth factor receptor 2: (a) Membranous and cytoplasmic staining (b) Cytoplasmic pattern of staining (c) Membranous pattern of staining (×200, human epidermal growth factor receptor 2)

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Table 1: Human epidermal growth factor receptor 2 expression with histologic subtype, grade, and stage of tumor in colorectal cancer (n=50)

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Of the eleven cases positive for HER2, ten (20%) were conventional adenocarcinomas, while there was one case (2%) of signet ring cell adenocarcinoma, respectively. The signet ring cell adenocarcinoma showed complete membranous HER2 positivity. A possible trend was seen between histological subtype and HER2 expression, however, no significant correlation could be established (P = 0.139) [Table 2].

Table 2: Correlation of human epidermal growth factor receptor 2 expression with histological subtype of tumor

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Of the eleven cases showing positivity for HER2/neu, seven, three, and one cases were moderately, well, and poorly differentiated adenocarcinomas, respectively. Of the cases positive for HER2, nine belonged to Stages III-IV and two to Stage II. Only four out of these eleven cases were positive for lymph node metastases. No correlation could be established between HER2 and tumor grade (P = 1.000) and tumor stage (P = 0.641), respectively [Table 3] and [Table 4].

Table 3: Correlation of human epidermal growth factor receptor 2 expression with tumor grade

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Table 4: Correlation of human epidermal growth factor receptor 2 expression with tumor stage

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Discussion

HER2 expression and its therapeutic implications have been studied in many tumors including breast, gastric, endometrial, ovarian, and pancreatic cancers. Tumors expressing HER2 or showing its gene amplification are considered aggressive tumors. trastuzumab or herceptin is a monoclonal antibody that acts against the membranous HER2 and not against the cytoplasmic HER2. This antibody is already FDA approved for HER2-positive breast and gastroesophageal adenocarcinomas.^[12]

Unlike breast cancer, despite there being a number of studies on HER2 expression in colorectal carcinoma, there are no specific guidelines for positivity on IHC expression of HER2. This is one of the reasons for the variable results of HER2 expression in colorectal cancer.

The mean age of patients in the present study was 51 years which was similar to the data obtained by Tu et al., Wu and Sun, Li et al., and Gill et al.^{[7],[8],[9],[13]} However, a higher mean age of 63–70 years was found in the Western population.^{[5],[14],[15]}

Histopathological typing was in concordance with the results of Gill et al. who demonstrated 77.5% conventional adenocarcinomas, 17.5% mucinous adenocarcinomas, and 2.5% each of signet ring cell adenocarcinomas and carcinoid.^[11]

Most of the patients in our study had histologic Grade 2 (56%), followed by Grade 1 (32%) and the least number of cases belonged to Grade 3 (12%). Jesus et al. reported tumor profile similar to our study with maximum number of Grade 2 tumors.^[5] Wu and Sun demonstrated the highest percentage of Grade 2 tumors. However, a reversal of ratio of Grade 1 to Grade 3 tumors contrary to our study was seen by them.^[8] Schuell et al. demonstrated maximum number of Grade 3 tumors (68%) and least number of Grade 1 tumors.^[16] Tu et al. had 86.7% well and moderately differentiated tumors and rest were Grade 3.^[7]

In our study, the highest number of patients (48%) were in Stage III at diagnosis, followed by Stage II (40%) with lowest number of patients being in Stage I (10%). We staged the patients according to CAP guidelines. Tu et al. reported 55.8% patients in Stage I/II and 44.2% cases in Stage III/IV that was similar to our study.^[7] Jesus et al. found Stages I, II, III, and IV as 25.6%, 18%, 25.6%, and 30.8%, respectively.^[5]

In our study, nine (18%) cases showed a weak-to-moderate cytoplasmic staining in more than 10% of tumor cells, one (2%) case showed a moderate combined cytoplasmic-membranous staining in >10% of tumor cells, while a single case showed complete membranous staining in >10% tumor cells. Gill et al. demonstrated 57.5% cases with cytoplasmic pattern of HER2 positivity while 7.5% cases with a combined cytoplasmic-membranous pattern. None of the cases in their study showed a complete membranous pattern.^[13] Li et al., Schuell et al., and Ochs et al. found a low HER2 positivity of 4%, 11%, and 15.5%, respectively, similar to our results.^{[9],[16],[17]} Wu and Sun found 46.2% positivity of membranous pattern, which could be attributed to the use of a polyclonal HER2 antibody unlike the present study where a monoclonal antibody was used.^[8]

Nathanson et al., Tu et al., Heppner et al., Kavanagh et al., Seo et al., Huang et al., and Zhang et al. also evaluated gene amplification by PCR/FISH following immunohistochemistry and obtained a low HER2 gene amplification ranging between 1.6–6%.^{[6],[7],[14],[15],[18],[19],[20]}

Kavanagh et al. found protein overexpression in 11% cases and gene amplification in 3% cases. They attributed higher protein expression to cytoplasmic HER2.^[15] Nathanson et al. demonstrated a protein overexpression in 3.6% cases with 2.4% cases showing HER2 amplification.^[6]

Trastuzumab (herceptin) seems to have a limited role to play in colorectal cancer, as it is active against the membranous HER2. Unlike breast and gastric cancer, colorectal cancer demonstrates a very low membranous HER2 positivity.

In concordance with the studies done by Jesus et al., Nathanson et al., Tu et al., Ochs et al., and Seo et al., we found no correlation between HER2 immunopositivity and clinicopathological variables such as TNM staging, grade, and lymph nodal status.^{[5],[6],[7],[17],[18]} Ochs et al. demonstrated a possible trend between histological subtype and HER2 as all HER2 positive cases in their study were conventional adenocarcinomas similar to the present study where majority constituted adenocarcinomas.^[17]

Wu and Sun demonstrated correlation between high HER2 expression and tumor size, stage, lymph node status, grade, distant metastasis, and invasion depth.^[8]

Li et al. found HER2 positivity to be correlated with tumor size and distant metastases.^[9] Similarly, Zhang et al. and Sun et al. found HER2 positivity to be associated with lymph node metastasis and advanced TNM staging, respectively.^[20],[21] This difference in results obtained by the above researchers could be attributed to a different ethnic group (Chinese population) in which the pathogenesis of colorectal cancer could differ from that in the Indian population.

Based on the results of the present study, no correlation was found between HER2 expression and clinicopathological variables such as histopathological subtype, stage, and grade of tumor.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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