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In the testis pure teratomas are rare, accounting for less than 7% of primary testicular tumours.1 This contrasts with the ovary, where 95% of germ cell tumours are pure teratomas.2 Teratomas do not always contain tissues representing all three germ cell layers. A monodermal teratoma is one that consists of only one germ cell layer, endoderm, mesoderm or ectoderm. The best recognised monodermal testicular teratomas are carcinoid tumours and primitive neuroectodermal tumours.3 Monodermal teratoma composed solely of cartilage is rare. We report a second case of purely cartilaginous teratoma and provide interphase cytogenetic evidence of its germ cell origin.
A 21‐year‐old man presented with a mass in his right testis. Blood chemistry tests showed an increased level of β‐hCG (641 IU/l; normal range 0–3 IU/l), and a normal level of α‐fetoprotein (2.4 ng/l; normal range 0.0–8.0 ng/l). The patient underwent orchiectomy followed by chemotherapy. Three months later, retroperitoneal lymph node dissection was done, removing a 275 g paracaval and interaortocaval mass, periaortic lymph nodes, and pericaval mass.
Sections 4 μm thick were cut from the paraffin block and stained with H&E. Immunohistochemistry for OCT4 was accomplished with a polyclonal goat anti‐OCT4 antibody (C20, sc8629; Santa Cruz Biotechnology, Santa Cruz, CA, USA; 1:500 dilution, 30 min at room temperature) directed towards the −COOH terminus of the protein, as previously described.4,5 Antigen retrieval was carried out by heating sections in 1 mmol/l EDTA (pH 8.0). Endogenous peroxidase activity was inactivated by incubation in 3% H2O2. Non‐specific binding sites were blocked using Protein Block (DAKO Corp., Carpineteria, CA, USA). Immunohistochemistry for S100 protein was also performed (primary antibody 1:1000 dilution; 30 min incubation; DAKO). Antigen retrieval was performed by heating sections in pH 6.0 citrate buffer. The positive and negative controls performed appropriately for each procedure.
Fluorescence in situ hybridisation (FISH) was performed on the testicular tumour as previously described.6 Sections (4 μm) were prepared from buffered formalin fixed, paraffin embedded tissue block. The slides were deparaffinised prior to hybridisation. Dual‐colour FISH was performed by using a mixture of Spectrum Orange labelled centromeric α satellite DNA probe (CEP12 located at 12p11.1–q11, locus D12Z3) and Spectrum Green labelled subtelomeric DNA probes (Tel12 located at D12S2071) for chromosome 12p (probes from Vysis, Downers Grove, IL, USA).
The slides were examined using a Zeiss Axioplan 2 microscope (Zeiss, Göttingen, Germany) with these filters: SP‐100 DAPI, FITC MF‐101 for Spectrum Green (12p) and Gold 31003 for Spectrum Orange (CEP12) from Chroma (Chroma, Brattleboro, VT, USA). The images were acquired with a CCD camera and analysed with MetaSystem Isis software (MetaSystem, Belmont, MA, USA). Five sequential focus stacks with 0.4 μm interval were acquired and then integrated into a single image in order to reduce thickness‐related artefacts. The images were adjusted to reduce background through threshold adjustment; however, the relative signal intensity and signal locations were not changed.
From the tumour section, 100 nuclei were scored for signals from CEP12 (red) and 12p (green) under the fluorescence microscope with 1000× magnification, and the ratio between green and red signals was subsequently calculated. We analysed the spatial distribution of the green and red signals to detect the specific patterns of signal aggregation consistent with isochromosome 12p (i(12p)), as previously reported.1,6,7,8,9,10,11 The quantitative criteria to determine 12p overrepresentation were described previously.6,10,11,12 A classical seminoma specimen was used as a positive control for FISH analyses.
The cut surface of the testis revealed a 20×14×10 mm well‐circumscribed, white, lobulated rubbery mass located within the testicular parenchyma. Histological examination revealed the mass to be composed of mature cartilage (fig 11).). The remaining testicular parenchyma showed seminiferous tubules containing only Sertoli cells. No intratubular germ cell neoplasia, unclassified type (IGCNU) was visible. A focus of fibrous scar was present outside the cartilaginous tumour suggestive of a burnt‐out germ cell tumour.
The retroperitoneal lymph node dissection specimens showed necrosis and inflammation consistent with chemotherapy effect on metastatic germ cell tumour. No viable germ cell tumour was identified.
The cartilaginous tumour gave a negative reaction with antibodies to OCT4 but a positive reaction for S‐100 protein. The reaction for OCT4 and S‐100 protein was negative in non‐neoplastic seminiferous tubules.
Interphase cytogenetics analysis using FISH revealed that the cartilaginous testicular tumour was positive for i(12p) in 4% of cells and also had 12p overrepresentation with 12p/12 centromeric ratio of 1.63 (fig 11).
Presented here is a case of monodermal pure teratoma of the testis composed solely of mature cartilage. Only one similar tumour has previously been described.13 While the histological appearance leaves open the possibility of a benign cartilaginous tumour and the lack of intratubular germ cell neoplasia also might seem to point to that possibility, the presence of isochromosome 12p and overrepresentation of chromosome 12p are strong evidence that the tumour is a teratoma.14,15 In a study of 17 testicular teratomas by Cheng et al,6 76% showed i(12p) and 29% had 12p overrepresentation (overall 88% of teratomas studied revealed 12p abnormalities). As seen in fig 11,, this tumour is positive for both isochromosome 12p and 12p overrepresentation. More than 80% of post‐pubertal teratomas are associated with intratubular germ cell neoplasia, and intratubular germ cell neoplasia was present in the testis containing the pure cartilaginous teratoma described by Singh et al.13 The present case is unusual in having no intratubular germ cell neoplasia.
Postpubertal teratomas, regardless of their appearance, have a 22–37% incidence of metastasis. If a scar from a burnt‐out germ cell tumour is also present, as in this case, the chance of metastasis increases to 66%.1 A study of patients with low‐stage primary pure teratomas of the testis revealed the overall risk of lymph node metastasis to be 40% at retroperitoneal lymph node dissection. This was also associated with a 16% relapse rate following retroperitoneal lymph node dissection.16 The pathologist must keep in mind that in patients with pure testicular teratoma, metastases may consist of other types of germ cell tumours.17
Competing interests: None declared.