The frequency of intratubular embryonal carcinoma: implications for the pathogenesis of germ cell tumours.

Aims: To define the frequency and distribution of intratubular embryonal carcinoma (IEC) in an attempt to shed light on the pathogenesis of non-seminomatous germ cell tumours (NSGCTs). Intratubular germ cell neoplasia of unclassified type (IGCNU) is common in NSGCT; however, IEC is rarely described.

Methods And Results: Sixty-two germ cell tumours were reviewed. Immunochemistry for CD30, placental alkaline phosphatase (PLAP) and c-kit was performed. The distribution, immunohistochemistry and morphology of the intratubular neoplasia were noted. All cases showed widespread IGCNU with PLAP and c-kit staining. CD30 showed strong focal intratubular positivity in 20/31 NSGCTs, 1/29 seminomas and 1/4 mixed seminomas/NSGCTs. In 17 of these cases, the CD30+ tubules were not easily identified as IEC on routine stains. These tubules were scanty in number and c-kit was negative, though some showed patchy PLAP staining. The cells within these tubules differed morphologically from IGCNU.

Conclusions: IEC defined by CD30 positivity is not always easily identified on haematoxylin and eosin staining. We suggest that IEC is a common intermediate step between IGCNU and NSGCTs. The patchy and focal distribution of IEC suggests it may evolve quickly to invasive disease.