BRIEF REPORT |
Correspondence to: Xavier Leroy, Service d'Anatomie Patholo-gique, Faculté de Médecine, Pole Recherche, rue Polonovski, CHRU, 59045 Lille, France. E-mail: x-leroy@chru-lille.fr
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Summary |
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Germ-cell tumors are the most common malignant neoplasms of the testis. Seminomatous and non-seminomatous tumors must be differentiated because the treatment and the prognosis are different. In light microscopic examination, seminoma may sometimes be difficult to distinguish from the solid pattern of embryonal carcinoma (EC). Although studies have shown that CD30 was a good marker of embryonal carcinoma and that c-kit was regularly expressed in seminoma, none has described the value of CD30 and CD117 (c-kit) in combination for the differential diagnosis between EC and seminoma. We selected 25 pure seminomas, seven pure ECs, and seven mixed germ-cell tumors composed of seminoma and EC from our archives and studied their immunoreactivity for CD30 and CD117. We observed that 27/35 seminomas were CD117+/CD30-; none of the seminoma was CD117-/CD30+. Conversely, 11/14 ECs were CD30+/CD117- and none was CD30-/CD117+. Our findings suggest that CD117 and CD30 immunohistochemistry used in combination represents a valuable tool for distinguishing seminoma from EC.
(J Histochem Cytochem 50:283285, 2002)
Key Words: CD30, CD117, c-kit, seminoma, embryonal carcinoma
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Introduction |
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GERM-CELL TUMORS are the most common malignant neoplasms of the testis. Seminoma constitutes 3550% of all germ-cell tumors (
Proto-oncogene c-kit encodes a surface membrane tyrosine kinase receptor that is required in normal spermatogenesis. C-kit is regularly expressed in seminoma but rarely in non-seminomatous germ-cell tumors. KIT signal transduction appears to be an important pathway for carcinogenesis of seminoma (
Formalin-fixed, paraffin-embedded tissue from 25 pure seminomas, seven pure ECs, and seven mixed germ-cell tumors composed of EC and seminoma were selected from the files of the Department of Pathology, Lille University hospitals. All slides and pathological reports were reviewed for diagnosis. Immunohistochemistry (IHC) was conducted on 4-µm-thick paraffin sections using an automated immunostainer (ES; Ventana Medical Systems, Strasbourg, France). After deparaffinization, IHC was performed using a three-step undirected process based on the streptavidin-biotin complex. The primary antibodies used were CD30 (1:40, BerH2; Dako, Glostrup, Denmark), CD117 (1:50, Dako). Pressure cooker pretreatment in citrate buffer (pH 6.0) was performed for 1 min 30 sec. Endogenous peroxidase activity was suppressed by first incubating the specimen in 3% hydrogen peroxide. Slides were counterstained with hematoxylin. Positive and negative controls were added to each automated immunohistochemistry run. Negative controls consisted of slides run without the primary antibody. Mast cells were used as internal positive control for CD117 and an anaplastic large-cell lymphoma as positive control for CD30.
Immunostaining was evaluated by two pathologists (XL, DA) by determining the percentage of positively staining cells as follows: 0, no staining; +, 110% of staining cells; ++, 1150% of staining cells; +++, >50% of staining cells.
Of the seminomatous tumors, 23/25 pure seminomas were stained with antibody to CD117. The staining was often intense and diffuse with a membranous pattern (Fig 1). Six of seven seminomatous components in mixed germ-cell tumors were also stained with CD117. CD30 was positive in one pure seminoma; the staining was moderate and focal (less than 10% of tumor cells). Few seminomatous cells were also CD30-positive in one mixed germ cell tumor. A total of 27 seminomas were CD117+/CD30-, three seminomas were CD117-/CD30-, two seminomas were CD117+/CD30+, and none was CD117-/CD30+.
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Of the embryonal carcinomas, 6/7 pure ECs were positive for CD30 and 6/7 ECs in mixed germ-cell tumors were positive for CD30 (Fig 2). The staining was membranous and diffuse in the great majority, but in four cases the staining was weak and focal. All tumors except one were negative with CD117.
A total of 11 ECs were CD30+/CD117-, two were CD30-/CD117-, one case was CD30+/CD117+, and none was CD30-/CD117+.
The results of immunohistochemical staining are summarized in Table 1.
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Differentiation between seminoma and EC is very important in consideration of the therapeutic approach. Light microscopic examination remains the gold standard for the diagnosis, but in some cases the differential diagnosis between seminoma and the solid pattern of EC may be difficult (
In 1988, a study about CD30 expression in non-hematopietic tissues showed that CD30 was expressed by EC and not by seminomas (
In searching in the literature for a positive marker of seminoma, we find that c-kit (CD117) was regularly expressed in seminomatous cells (
In conclusion, we suggest that CD30 and CD117, used in combination, are helpful for the differential diagnosis between EC and seminoma.
Received for publication September 24, 2001; accepted September 26, 2001.
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