CD10 is deemed a useful immunohistochemical marker in the differentiation between BCC and SCC. In cases of positive CD10 in tumor cells, the diagnosis tends to be most likely BCC rather than SCC; this is clinically important because BCC is not as aggressive as SCC.4
In our study, CD10 was expressed diffusely in the stromal cells around the tumor nests of all the SCC cases.
Our study has an advantage over previous studies insofar as it investigated a large number of BCC and SCC cases and also included basosquamous cases. Furthermore, it is the only study of its kind to present the expression patterns of CD10 not only in BCC by comparison with SCC but also in BCC in comparison to TE. The comparison of the CD10 expressions between our SCC and BCC groups showed a significant difference between the CD10 expressions in the tumor cells (P<0.001) as well as stromal cells (P<0.001).
One previously conducted study, performed on 16 SCC cases and 17 solid, 2 morphoeic, and 2 adenoid types of BCC, concluded that the absence of CD10 expression in the tumor cells of SCC and infiltrating BCC and overexpression in the stromal cells might be due to the invasive properties of these tumors.4
In the present study, there was no significant difference in CD10 expression between the stromal and tumor cells of the BCC subtypes, which may be due to the small number of the subtypes in this study.
Although CD10 has been implicated in the pathogenesis of various lung and lymphoid neoplasms, further studies aiming at defining the exact role of CD10 in the pathogenesis of BCC and SCC as well as a study of an expanded number of these tumors are needed prior to adopting its application in the routine evaluation of these occasionally difficult cases.6
In another study, strong CD10 expression in the tumor cells of superficial BCC was mentioned to be probably in consequence of the indolent nature of these tumors, while lower levels of CD10 expression in the tumor cells were found in aggressive variants of BCC.5
One case of superficial BCC in our study exhibited strong CD10 expression of the tumor cells at the periphery of the tumor nests. One study reported the usefulness of CD10 for differential diagnosis between benign tumors of cutaneous appendages originating from the hair follicle and BCC as an immunohistochemical marker, especially in the small and superficial biopsies. Condensation of CD10-positive stromal cells was shown around basaloid nests, which was statistically significant in differentiating TE from BCC. Conversely, CD10-positive basaloid cells were seen predominantly in BCC. No BCC cases demonstrated stromal expression alone in that study, including only the nodular type. The expression of CD10 by peritumoral stroma alone favored a diagnosis of TE, whereas staining of basaloid cells supported a diagnosis of BCC.10
The results of the present study also showed a significant difference in CD10 expression between the TE and BCC groups in the tumor cells and stromal cells, while stromal expression alone occurred in 12 BCC cases. The results of a similar study showed that Bcl-2 failed to differentiate between trichoblastoma and BCC with follicular differentiation. In contrast, CD10 proved very useful for the detection of areas of basocellular proliferation with follicular differentiation, which could be misinterpreted as trichoblastoma. Consequently, it could help the pathologist to identify lesions of different malignancy in patients who are likely to benefit from a more suitable treatment.11
Elsewhere in the literature, one study retrieved 30 cases of benign tumors of cutaneous appendages originating from the hair follicle and 30 cases of BCC. The stromal CD10 immunopositivity of the benign tumors of the cutaneous appendages originating from the hair follicle was stronger than that of the BCC cases (P=0.003) with respect to both the numerical and the degree of expression. However, the peripheral CD10 of the BCC cases was stronger than that of the benign tumors.10
In the current study, we found that all TE cases demonstrated strong CD10 staining of the stromal cells with accentuation around the tumoral nests, but no TE tumor cell staining. In another study, the CD10 expression pattern was analyzed in 23 cases of nodular type BCC and 13 cases of TE. CD10 expression by peritumoral stroma alone favored a diagnosis of TE, whereas staining of basaloid cells supported a diagnosis of BCC.9
In our BCC group, expression of CD10 by tumor cells was observed in 42 out of 55 cases (76%) with mostly peripheral staining (61%). Diffuse stromal only staining for CD10 was witnessed in 12 cases of the 55 BCCs (21%), 4 of them being basosquamous cell carcinoma. This finding does not chime in with the Pham et al. study,9
in which no “stromal cell alone” staining was seen in a total of 23 BCC cases. Their study contained a smaller number of cases and did not include basosquamous cell carcinoma. In our study, two cases were diagnosed as trichoblastoma, a tumor commonly mistaken for nodular BCC. CD10 staining of these two tumors showed only epithelial staining in the outermost basaloid cells, similar to the typical cases of BCC. In one study, there was a large number of trichoblastoma diagnosed with hematoxylin and eosin, which were reclassified as BCC and BCC-FD with CD10 immunostaining.11
The authors stated that this pattern might reflect the differences in stromal expression between the two lesions, which may be a result of the different regulation of tumor growth or host response.11
Eighteen cases of morphoeic basal cell carcinoma and 19 cases of desmoplastic trichoepithelioma were studied by Costache et al.12
who concluded that the expression of CD10 was a reliable indicator for the diagnosis of morphoeic basal cell carcinoma only when the expression was present in the aggregations of cells, whereas stromal reactivity was not a useful marker for differentiation. We did not have a desmoplastic type of TE. Be that as it may, one out of three cases of morphoeic basal cell carcinoma showed epithelial staining. Our study also showed that stromal reactivity may not be a useful marker for differentiation.
CD10 is also regarded as a myoepithelial-specific marker; and in some studies, it is described as involving benign eccrine tumors. Bahrami,13
showed that CD10 was beneficial in distinguishing metastatic cutaneous renal cell carcinoma from skin tumors with eccrine and apocrine differentiation, but not tumors with sebaceous differentiation. Recently, the expression of CD10 has been reported in a variety of epithelial and mesenchymal neoplasms. CD10-positive epithelial neoplasms include renal cell carcinoma, hepatocellular carcinoma, urothelial carcinoma, and prostatic carcinoma.8,14
CD10 has been allied to tumor progression and metastasis in different tumors. For example, a significant positive relationship has been found between CD10 expression and Breslow thickness, Clark level, and ulceration in malignant melanoma.15
In the oral cavity SCC, CD10 stromal positivity is correlated with the presence of metastasis, local recurrence, and high tumor grade.16
In one study, CD10 expression was investigated in 20 cases of cutaneous SCC of different grades (well, moderately, and poorly differentiated), and the authors concluded that 1) stromal expression of CD10 is not lost in deeply invasive SCC, as previous literature suggested; and 2) lack of cytoplasmic expression of CD10 by cutaneous SCC can be considered as an additional prognosis factor to investigate in the future.17
In another study, CD10 was expressed in the stromal cells of a total of 9 SCC cases.8
In the current study, immunoreactivity was detected in the stromal cells of all the 50 SCC cases. Nevertheless, in the tumor cells at the center of the epithelial nests, immunoreactivity was detected in 5 cases (10%), which were placed focally in less than 10% of the tumor cells.
In future studies, we aim to investigate CD10 expression in SCC groups of low and high risk according to the degree of differentiation, size, and depth of invasion (perineurial and lymphovascular invasion).18
CD10 expression will be compared between these groups.