Introduction

Basal cell carcinoma (BCC) is the most frequent cutaneous neoplasm, accounting for around 70% of all skin cancers. It is regionally aggressive and its metastases are rare (1). The second most common malignancy in humans is cutaneous squamous cell carcinoma (SCC), with around double metastases compared to BCC (2). Therefore, BCC and SCC are the most commonly found tumoral entities in cutaneous medicine. They are commonly well-recognized on the basis of their clinical and histopathological features and differentiation between these two carcinomas is clinically important as there is a significant difference in their rates of aggressiveness and metastatic potential. In case of difficulties in the differential diagnosis between the two entities; in addition to the well-defined histological criteria, immunohistochemistry (IHC) methods can be of help and, in the literature, many studies have previously reported their role (3-5). The cluster of differentiation 10 (CD10) is an enzyme of the cell surface with metalloendopeptidase activity and reduces cellular response to peptide hormones by regulating local peptide hormone concentrations (4). CD10 is correlated with biological invasions in human malignancies, but this marker is more commonly used for diagnosis and prognosis with a more complexity (6). B-cell lymphoma-2 (Bcl-2) protein suppresses cell death and thus may be considered to allow malignant cells for proliferation (7). In addition, Bcl-2 protein preserves cell against apoptosis caused by various death-inducing signals (8). Carcinoembryonic antigen (CEA) is a complex macromolecule with high glycosylation and is used as a marker in carcinomas worldwide (9). Epithelial membrane antigen (EMA) is another highly glycosylated protein with expression mainly in normal and tumor epithelium (10). The differences in biologic behavior mandate the application of more accurate diagnostic methods distinguishing between SCC and BCC. In the literature, there was just one study (11) that checked EMA, CD10, CEA, and Bcl-2 markers together and other studies used one or two markers for distinguishing between cutaneous BCC and SCC. Therefore, the present systematic review aimed to assess the expression of EMA, CD10, CEA, and Bcl-2 in distinguishing cutaneous BCC from SCC.

This systematic review was achieved based on the guidelines for the Preferred Reporting Items for Systematic Reviews and Meta-Analyses PRISMA (12).

Search strategies

A comprehensive search was conducted starting from 1983 to September 2017 using the search terms of “squamous cell carcinoma” (or “SCC”) or basal cell carcinoma (or “BCC”) and “EMA” (or “epithelial membrane antigen”) or “CEA” (or “carcinoembryonic antigen”) or “CD10” (or “cluster of differentiation 10”) or “Bcl-2” (or “B-cell lymphoma 2”) in the PubMed/Medline, Web of Science, and Scopus databases without language restriction. In addition, we manually checked the references of eligible articles to our subject for finding possible missed studies.

Study selection and eligibility criteria

One author (M.S) searched and selected the relevant studies. The second author (M.R) re-checked the studies. All articles in this study were examined for the evaluation of the expression of EMA, CD10, CEA, or Bcl-2 in distinguishing between cutaneous BCC and SCC. The studies included in the systematic review involved the following inclusion criteria: a) cross-sectional design; b) human tissue; and c) IHC staining of EMA, CD10, CEA, or Bcl-2. The exclusion criteria were as follows: a) duplication of a previous publication; b) review or case-series; c) conference paper; d) no full-text; and e) no relevant data.

Data extraction

Two authors (M.S & M.R) checked the studies involved in the systematic review and extracted the relevant data. The third author (E.Z) re-checked the data. We extracted the author’s name, publication year, country, the number of BCC or SCC patients/tissues; the number of BCC or SCC tissues with positive IHC of each marker, used antibody and cut-off from each study were included in the systematic review.

Quality assessment

The quality of each study was evaluated by the Newcastle-Ottawa Scale (13). One author (M.R) checked the quality of the studies. The maximum total score was nine for cross-sectional studies. A high-quality study was considered as a study with ≥7 scores.

Statistical Analysis

The data were analyzed applying SPSS version 22 software (IBM Corp., Armonk, NY, USA) and the chi-square test. P <0.05 (two-sided) was considered statistically significant.

Results

Study selection

Out of 250 studies retrieved in the databases, after excluding duplicates and not relevant studies, 38 full-text studies were assessed for eligibility (Figure 1). Then, seven studies were excluded for some reasons (one article was animal study, two articles were review studies, two articles reported mean score of markers, one article mixed BCC and SCC patients as one group, and one article duplicated with another study). At last, a total of 31 studies were entered and analyzed in the systematic review.

Characteristics of the studies

The characteristics of the 31 studies covered in the systematic review are presented in Table 1. The studies were published between 1983 and 2017. Eight studies (3,14-20) were from USA, four (4,5,11,21) from Iran, three (22-24) from UK, three (25-27) from Japan, two (28,29) from Turkey, two (30,31) from Egypt, and also Australia (32), Austria (33), Netherlands (34), Taiwan (35), China (36), Croatia (8), Romania (37), India (38), and Germany (39) each with one study. All studies in the systematic review included 694 BCC and 536 SCC patients/tissues. Fifteen studies reported Bcl-2 and included 339 BCC and 263 SCC patients; eight studies reported CD10 and included 257 BCC and 180 SCC patients; five studies reported CEA and included 111 BCC and 87 SCC patients; and ten studies reported EMA and included 177 BCC and 158 SCC patients. Other characteristics such as the number of patients/tissues with positive staining for each marker, used antibody and cut-off are shown in Table 1.

IHC staining

The pooled staining of biomarkers based on mentioned cut-offs in each study showed that staining results of EMA and CEA in SCC tissues were significantly more positive than BCC tissues (p<0.00001 and p=0.008, respectively), as well as CD10 and Bcl-2 in BCC tissues, were significantly more positive than SCC tissues (p<0.00001 and p<0.00001, respectively) (Table 2). Therefore, these markers can be useful biomarkers for distinguishing between both BCC and SCC.

Quality assessment

The quality assessment of each study is shown in Table 3. A mean score of 6.7 was reported for all studies and twenty-six studies had high quality.

Discussion

It is critical to differentiate SCC from BCC clinicopathologically (21). In most cases, the differentiation of SCC and BCC is straightforward in routine H&E staining (4). The distinction of these neoplasms is clinically important because of the more aggressive behavior and metastatic potential of SCC, which mandates more radical treatment and closer follow-up (4,21). The SCC recurrence rate is about twice higher than that of BCC. So, more aggressive treatment is needed for SCC (21). Due to similarity in histopathology, differentiation between SCC and BCC is sometimes difficult (30). In fact, keratotic and metatypical BCCs may be indistinguishable from basaloid SCC (bSCC) in routine histopathology slides (3,4). Therefore, differentiation between BCC and SCC is mostly performed by routine histopathology, which may cause difficulty in superficial small biopsies. CD10 and Bcl-2 markers are of benefit in this condition (31). The present systematic review evaluated IHC staining of four biomarkers including EMA, CD10, CEA, and Bcl-2 in BCC compared to SCC tissues. BCC presentation is typically an ulcerated pearly papule/nodule with telangiectasia (40,41). SCC presentation is typically shallow crusted ulcer with raised margin accompanying actinic damage (40). Differentiation between SCC and BCC is very important in clinic and laboratory (21,30). Out of ten studies in systematic review to check EMA (11,18-20,22-24,27,28,39), five studies (22,23,27,38,39) showed EMA as positive in ≥90% SCC tissues and eight studies (12,20,21,25,28-31) did not show EMA as positive in BCC tissues (0%). In addition, out of five studies that checked CEA (11,22,23,27,32), two studies (22,32) showed CEA as positive in ≥80% SCC tissues and three studies showed ≤10% BCC tissues. Out of eight studies included in the systematic review that checked CD10 (3-5,21,26,30,31), six studies (3,5,21,26,30,31) reported CD10 as positive in more than 85% BCC tissues and five studies (3,5,11,26,31) did not show CD10 as positive in SCC tissues (0%). In addition, out of fifteen studies that checked Bcl-2 (8,11,14-17,25,28,29,31,33-37), thirteen studies (8,11,14,17,25,28,31,33,35-37) identified Bcl-2 as positive in ≥80% BCC tissues and eight studies (8,14,15,17,31,33,35,36) identified Bcl-2 as positive in ≤10% SCC tissues. Therefore, BCC and SCC can be readily distinguished using routine IHC for these markers. Based on the results of the systematic review, at least, if tumor cells were CD10 and BCl-2 positive, this would favor BCC over SCC and if tumor cells were EMA and CEA positive, this would favor SCC over BCC diagnosis.

 In most cases, BCCs and SCCs are manifested on sun-damaged skin, suggesting a main role for ultraviolet (UV) radiation and their incidence is rising in Whites (37,40). UV-rays, for example, trigger new mechanisms (molecular changes in protein structure, the release of proinflammatory cytokines, and oxidative stress) overlapping those of the cutaneous carcinogenesis process (37).

Basosquamous carcinoma (bSCC) of the skin is an uncommon variant with histopathological aspects of BCC and SCC. Some authors consider it as a variant of BCC, while others as an aggressive entity (42). In the research of Beer et al. (23), a panel of antibodies was used. They found that all cases of BCCs were stained positively for the Ber EP4 antibody (Antibody to Ep-CAM/Epithelial Specific Antigen), with no staining of SCCs. bSCC demonstrated areas of BerEp4 positivity. In this paper, BCCs did not stain with EMA, but most of the SCCs did. Only one bSCC showed a focal EMA positivity. The authors concluded that the distinction between BCCs and SCCs was possible by using BerEp4 and EMA, and that identification of bSCC could also be achieved with these antibodies.

Another challenging entity is bSCC, a quite rare type of SCC, which may resemble BCC with squamous metaplasia. In this context, BerEp4 is unreliable for differentiation between the two entities, and adding the staining for cytokeratin 14 (CK14) or CK17 is needed for differentiation (43). In this regard, Winters et al. (44) have reported the use of BerEp4 as a helpful diagnostic marker for bSCC as positive in 82% of their cases, but also in 68% of SCC cases. Positivity of BerEp4 was also found in 26.3% of cases in Bowen disease, a variant of SCC in situ, and caused difficulty in differentiation from BCC and other keratinocyte neoplasms (45). Stanoszek et al. (46) reviewed the histologic mimics of BCC including non-neoplastic processes (i.e., follicular induction over dermatofibromas), benign adnexal tumors (mainly of follicular origin), and cutaneous carcinomas with basaloid appearance. Distinguishing required clinicopathological correlation and IHC. A panel including PHLDA1 (Pleckstrin Homology Like Domain Family A Member 1), CK20, androgen receptor, CD10, Bcl-2, CD34, Ber-EP4, CD200, Claudin 4, EMA, CK15, and CEA was successfully used for a wide range of diagnoses. The limitations of this study were as follows: 1) in most studies, there was no sensitivity and specificity of markers between SCC and BCC, 2) sensitivity and specificity of used antibodies were different among the studies and 3) in some studies, the cut-off of markers was different. The strengths of this study were as follows: 1) most of the studies had high quality, and 2) the used method in all studies was similar (IHC).

Conclusion

The findings of the systematic review presented a high efficiency of EMA, CD10, CEA, and Bcl-2 markers in differentiating between SCC and BCC. Moreover, the use of these markers will be useful in such cases that routine microscopy cannot differentiate between the two mentioned carcinomas. Further larger studies in various environmental areas are needed to reach more precise estimates of the sensitivity and specificity of these markers.

Acknowledgement

In addition, the authors would like to thank the Clinical Research Development Center of Imam Reza Hospital for Consulting Services.

Ethics

Peer-review: Externally peer-reviewed.

Authorship Contributions

Concept: M.R., E.Z., Design: M.S., Data Collection or Processing: M.R., M.S., Analysis or Interpretation: M.R., E.Z., Literature Search: M.S., Writing: M.S.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.