|Year : 2014 | Volume
| Issue : 2 | Page : 40-44
Immunohistochemistry Panel for Differential Diagnosis of Basal Cell Carcinoma and Trichoblastoma
Maria Elisa Vega Memije1, Eduwiges Martinez Luna2, Oslei Paes de Almeida3, Adalberto Mosqueda Taylor4, Juan Carlos Cuevas Gonzalez5
1 Department of Dermatology, Hospital General Dr. Manuel Gea González, Mexico
2 Department of Dermatology, Hospital General Dr. Manuel Gea González, Brazil
3 Department of Oral Pathology, University of Campinas, Piracicaba, São Paulo, Mexico
4 Department of Pathology and Oral Medicine, Universidad Autónoma Metropolitana, Mexico
5 Medical Dental and Health Sciences, National Autonomous, University of Mexico, Mexico, Mexico
|Date of Web Publication||13-Aug-2014|
Maria Elisa Vega Memije
Department of Dermatology, Hospital General Dr. Manuel Gea González, Calzada de Tlalpan 4800, Sección XVI Delegación Tlalpan, D.F. C.P 14080
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: Basal cell carcinoma (BCC) is the most common malignant neoplasm in the skin and is considered to have a low degree of malignancy. BCC is invasive but rarely metastatic and originates in hair follicle-derived cells or interfollicular zones of the epidermis. Trichoblastoma (TB) is an infrequent benign skin neoplasm that differentiates toward follicular germinative cells. Both of these cutaneous lesions comprise nests of basaloid cells, and because the differential diagnosis is hard to obtain between them histologically due to their similarity, the correct diagnosis must be established. Materials and Methods: The sample size of this descriptive study consisted of 20 cases: 10 paraffin-embedded tissues that were diagnosed with carcinoma of solid basal cells with follicular differentiation and 10 TB tissues. The diagnosis of all samples was confirmed morphologically with hematoxylin and eosin. One-micron-thick sections were cut from each sample and analyzed semiquantitatively by immunohistochemistry (IHC). Differences in staining between BCC and TB were analyzed by Chi-square test. Results: Two of 10 TB cases were positive for Ki-67 versus 10 of 10 BCC samples. Cytokeratins 6 was expressed in 1 of 10 TB samples and in all BCC tissues. Staining with clone 34BE12 generated signals in all lesions at various intensities. Conclusion: The diagnosis between TBs and BCCs must be made histologically, because the treatment of BCC is radical and can compromise aesthetics and function, even for experienced pathologists. Because their morphological diagnosis is difficult, the histopathology results must be supported by an IHC panel.
Keywords: Basal cell carcinoma, immunohistochemistry, trichoblastoma
|How to cite this article:|
Vega Memije ME, Luna EM, de Almeida OP, Taylor AM, Cuevas Gonzalez JC. Immunohistochemistry Panel for Differential Diagnosis of Basal Cell Carcinoma and Trichoblastoma. Int J Trichol 2014;6:40-4
|How to cite this URL:|
Vega Memije ME, Luna EM, de Almeida OP, Taylor AM, Cuevas Gonzalez JC. Immunohistochemistry Panel for Differential Diagnosis of Basal Cell Carcinoma and Trichoblastoma. Int J Trichol [serial online] 2014 [cited 2019 Nov 18];6:40-4. Available from: http://www.ijtrichology.com/text.asp?2014/6/2/40/138583
| Introduction|| |
Basal cell carcinoma (BCC) is the most common malignant neoplasm of the skin and is considered to have a low degree of malignancy. BCC is invasive, rarely metastatic, and originates in hair follicle-derived cells or interfollicular zones of the epidermis;  it generally appears after the fourth decade of life. The most commonly affected sites are the face, scalp, neck, auricles, chest, and back. Its clinical appearance is polymorphic and ranges from an erythematous plaque with moderate desquamation to an ulcerated exophytic tumor with variable hyperpigmentation and the presence of small pearly lesions that constitute and delimit it clearly at its border. BCC is a carcinoma of superficial, extensive growth that leaves areas with an atrophic appearance and does not invade deeply, except for the infiltrating variant. 
Trichoblastoma (TB) is an infrequent benign skin neoplasm with differentiation toward follicular germinative cells. The clinical diagnosis is difficult to make, because it appears as small, nonulcerated, adjacent skin-colored papules or neoformations that generally affect the face and scalp, and it is not distinguished by specific clinical data. TB is usually an isolated lesion, but it can also appear as multiple lesions. 
Both cutaneous lesions comprise nests of basaloid cells; thus, their histological differential diagnosis is complicated due to their similarity. A correct diagnosis must be established, because the treatments for each condition differ and can affect one's aesthetics and function. The conservative treatment for TB is simple surgical resection, whereas, for BCC, free margins must be achieved, because it is a carcinoma and in general, its management differs because it is a malignant neoplasm. 
Histologically, TB is a neoplasm with benign characteristics and is symmetrical and well-delimited, with retraction clefts between the tumor stroma and the adjacent healthy dermis. TB consists of an epithelium of follicular germinative cells and a densely fibrocytic stroma that usually shows follicular differentiation toward follicular bulbs and papillae, respectively.  BCC shares certain histopathological properties, such as the presence of a fissure between the epithelium and stroma, retraction of epithelial nests and cells in a palisade arrangement in the periphery of the tumor. Other characteristics that are helpful in making a morphological diagnosis of these lesions are necrosis of individual cells and mitosis, both of which are related to BCC, although the diagnosis remains challenging, necessitating an immunohistochemical (IHC) panel. 
Several groups have proposed IHC markers that facilitate the differential diagnosis of TB and BCC, but there are no specific antibodies that can be used reliably. 
Immunohistochemical markers have been examined about the diagnosis of and differentiation between BCC and TB. Some groups have focused on the pattern of expression of cytokeratins (CK5, CK6, CK14, and CK19), but no differences among these antibodies have been seen about BCC and TB (positivity in basaloid cells), likely because these pathologies share a pattern of histogenesis, both being derived from germinative cells of the hair follicle. 
This study was performed to identify antibodies that have diagnostic value in differentiating between BCC and TB.
| Materials and methods|| |
This sample of this descriptive study comprised of 20 cases - 10 with a diagnosis of solid BCC with follicular differentiation and 10 that were diagnosed with TB - based on a search of paraffin blocks from patients with clinical and histological criteria of BCC and TB. In all cases, the diagnosis of both lesions was confirmed by identification of histopathological characteristics in hematoxylin and eosin-stained slides. Subsequently, the corresponding cuts were (1 μ) for IHC. The tissues were deparaffinized and rehydrated; antigen retrieval was performed with sodium citrate at 0.1%, pH 6.2; endogenous peroxidase was blocked (0.9% hydrogen peroxide); and the tissues were immersed in bovine serum albumin at 1% to block nonspecific sites. All washes were performed with phosphate buffered saline.
Tissue samples were incubated with the primary antibodies for 18 h at 4°C; their dilutions are shown in [Table 1]. Later, anti-mouse/anti-rabbit secondary antibody and streptavidin/peroxidase complex were added sequentially for 30 min. The reaction was visualized with diaminobenzidine (Dako) and counterstained in Carazzi's hematoxylin.
The IHC results were analyzed semiquantitatively. Expression was scored positive - mild +, moderate ++ and severe +++ or negative. The database was created with the SPSS version 13, Inc., Chicago, IL, USA to analyze the association between antibodies and BCC and TB. Chi-square test was performed for these qualitative variables.
| Results|| |
Two of 10 TB cases were positive for Ki-67 antibody was positive in 2/10 TB, compared with all 10 BCC cases. CK6 was expressed in 1 or 10 TB and all 10 BCC cases [Figure 1] and [Figure 2]. Clone 34BE12 stained both lesions in all 10 cases at varying intensities [Figure 3]. There were significant differences in these three antibodies; the levels of intensity in both pathologies are shown in [Table 2].
|Figure 1: Basal cell carcinoma (BCC) (a and b) (×40). Expression of Ki-67 in basal cells of epithelial islands. Ki-67 was positive in 100% of BCC versus 20% of trichoblastoma|
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|Figure 2: Cytokeratins 6 (CK6). Basal cell carcinoma (BCC) (a and b) (×10), (c and d) (×40). Reaction to CK in 90% of BCC versus 10% of trichoblastomas|
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|Figure 3: 34BE12. (a) ×10 and (b) ×40. Intense immunostaining in epithelial nests of basal cell carcinoma. (c) ×10 and (d) ×40. Positive reaction in islands and cords of trichoblastoma cases|
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Cytokeratins 1, CK5, CK7, CK14, CK19, and p53 were expressed similarly in TB and BCC [Table 3].
|Table 3: Intensity of CK1, CK5, CK7, CK14, CK19, and p53 antibodies in TB and BCC |
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Cytokeratins 10 was positive in the lining epithelium and hair follicles, and CD34 was positive in peripheral blood vessels, but both proteins were absent in tumor cells. CK20 was not expressed in tumor cells, for which there were no positive internal controls.
| Discussion|| |
There are many dermatopathological conditions, some of which have similar histopathologies. IHC is a vital tool in the diagnosis, differential diagnosis, and prognosis of many benign neoplasms and skin cancers. IHC is also the best technique for determining the origin of a tissue or the differentiation of neoplastic cells. 
Many studies have compared the expression of CK between CBC and TB but have not reported any differences. 
Consistent with Schirren et al., we did not observe any differences in CK5, CK14, and CK19 expression between pathologies, but we noted significant differences in CK6, which was expressed in 10% of TB versus 90% of BCC cases. One explanation is that CK6 is a hyperproliferative CK, and under normal conditions, it is detected in the plantar epidermis, hairy zones, nails, and nonkeratinized stratified epithelium. There are three isoforms of CK6-6a, 6b, and 6c - each encoded by a different gene.
The increase in CK6 and CK16 in hyperproliferative epidermal disorders has been reported by some groups. 
CD34 is a 115-kD intercellular adhesion protein that expresses glycoproteins in immature hematopoietic cells and endothelial cells. Anti-CD34 has been used in the diagnosis of solitary fibrous tumors, desmoplastic mesothelioma, hemangiopericytomas, and endometrial sarcomas. In 2010, using anti-CD34, Sengul et al. did not observe any differences between nodular, superficial, infiltrating, and mixed BCCs versus benign tumors of cutaneous appendages of the hair follicle (trichoepithelioma [TE], TB, trichoadenoma and trichofolliculoma).  Our results were similar, wherein CD34 was absent from TB and BCC tumor cells, but was expressed at the periphery of the tumor.
Gerdes et al. described a mouse monoclonal antibody against Ki-67 a nuclear antigen in actively proliferating cells. In mitogen-stimulated cells, they demonstrated that the antibody recognized an antigen that was expressed in all phases of the cell cycle, but not react with quiescent cells or cells in early G1 phase that had been stimulated with mitogens. 
In 2000, Abdelsayed et al. analyzed antibodies to bcl-2, Ki-67, proliferating cell nuclear antigen (PCNA), and p53 and found significant differences in bcl-2, Ki-67, and PCNA expression between TB and BCC, concluding that PCNA and Ki-67 can be used for the differential diagnosis of these pathologies, unlike p53 and bcl-2, the expression of which was similar.  Similarly, we found that Ki-67 was expressed in 100% of BCC cases versus 20% of TBs, although p53 had greater positivity in BCC, albeit insignificantly (40% vs. 10%, respectively).
Our findings are consistent with those in the literature that Ki-67 is a marker of cell proliferation that expressed at higher levels in malignant tumors compared with benign neoplasms. Thus, pathologists can use anti-Ki-67 to differentiate BCC and TB.
CK20 is a marker of Merkel cells,  gastric adenocarcinoma, and metastatic carcinoma and has been used to differentiate certain forms of TB, TE, or fibroepithelioma from BCC, which rarely expresses CK20.  None of our cases was CK20-positive cases; thus, we could not determine whether it has diagnostic value.
CK7 is expressed in a wide variety of simple epithelia. Skin spinocellular carcinomas are usually negative for this CK7, whereas those that originate in other nonkeratinizing squamous epithelia are positive. CK7 is a very sensitive and specific marker of neoplastic cells in mammary and extramammary Paget disease,  prompting us to examine it. However, we did not obtain conclusive data with anti-CK7, because it was expressed in only one case of BCC and TB.
CK1 and CK10 expression has been reported in neoplasms with follicular differentiation (TB and BCC), but they cannot be differentiated, based on these markers, because their expression pattern is nearly identical in these pathologies.  In this study, we had one mildly CK1-positive case (BCC), and withal samples were CK10-negative.
Clone 34BE12 reacts with cytoplasmic high-molecular-weight CK in basal cells, and it has been used widely as an auxiliary marker in the diagnosis of adenomas and adenocarcinomas, because it recognizes basal cells in prostate glands.  This antibody stained positively in both pathologies, but the signal intensities differed: In 90% of BCCs, the binding was high and moderate in 10%, whereas 80% of TBs had mild immunostaining and 20% had moderate signals. That CK6 and 34BE12 have disparate expression patterns between TB and BCC is notable, because these markers have not been considered in distinguishing pathologies.
A histological diagnosis between TBs and BCCs must be made, because the treatment for BCC is radical and can compromise aesthetics and function, even for an experienced pathologist. Their morphological diagnosis is not always easy, necessitating an IHC panel to support the histopathology results. Based on our findings, we propose the use of Ki-67, CK6, and 34BE12 antibodies as diagnostic aids to differentiate between TB and BCC, Ki-67 and CK6 are expressed in BCC and 34BE12 stains intensely in BCC and mildly positively in TB.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]