Case 3 -

Nephroblastoma (Wilms tumor) arisen in a Teratoma Gregor Mikuz Medical University Innsbruck Innsbruck, Austria

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26-year old patient suffered a scrotal trauma playing soccer. 6 months later sudden onset of painful testicular swelling. The family physician diagnosed a posttraumatic epididimorchitis and prescribed a therapy with antibiotics. One week after beginning of the therapy the scrotum is still rapidly swelling and the scrotal skin becomes necrotic (see photography) . The patient is referred to the urological clinic where a testicular tumor clinical stage II is diagnosed and a tumor orchidectomy with partial resection of the scrotum is carried out. The gross specimen consists of an amorphous tumour mass with the greatest diameter of 20 cm and a weight of 820 g. The mass is partially covered by a small skin strip. The anatomical structures epididymis and testis are completely destroyed and overgrown by the tumor. The cut surface of the tumor is gray-tanbrownish and shows extensive necrosis. Some few scattered cartilaginous areas in the tumor can be macroscopically detected.. Case 3 - Slide 1 Click to view with ImageScope Click to view with a Web-Based Viewer Case 3 - Figure 1 The appearance of the swollen scrotum with the testicular tumor protruding trough the skin. Case 3 - Figure 2 Low power view of the rather undifferentiated tumor Case 3 - Figure 3 Higher power with primitive tubular structures surrounded by undifferentiated tumor cells. Case 3 - Figure 4 Low power view with tubular structures and structures mimicking primitive glomeruli (right corner at the bottom). The insert shows the positive immunohistochemical reaction of the tumor cells with the CD 99 antibodies. Case 3 - Figure 5 Vascular invasion of the tumor masses. Case 3 - Figure 6 Another low power view of the tumor. Case 3 - Figure 7 Areas with spindled tumor cells resembling smooth muscle cells. Case 3 - Figure 8 The spindled cells stain positively with desmin antibodies. Case 3 - Figure 9 Low power view of tubular structures immunohistochemically stained with cytokeratin antibodies (CAM 5.2) Case 3 - Figure 10 Higer power with tubular structures positively stained with cytokeratin antibodies (CAM 5.2). Case 3 - Figure 11 Small immature glomeruli - like structures. Diagnosis : Nephroblastoma (Wilms tumor) arisen in a Teratoma Comment: The WHO 2004 [1] classification distinguishes two types of testicular nephroblastomas – such arising in a teratoma or paratesticular nephroblastomas developing from ectopic kidney anlage (primordium). Foci of nephroblastoma can be often found in immature parts of teratomas. Rarely, however, the testicular germ cell tumour consists more or less only of nephroblastoma tissue. Such "non germ cell malignancy within a germ cell tumor" [2]are found in about 3% of testicular germ cell tumors [3]. Theoretically any type of carcinoma or sarcoma and even carcinoids can develop within a teratoma. The most frequent observed are rhabdomyosarcomas and primitive neuroectodermal tumors [4]. This is not surprising because teratomas usually abound in neural and muscle tissue. Epithelial malignancies like adenocarcinoma or squamous carcinoma are, however, rather rare. Somatic type malignancies have been observed also in the lymphnode metastases after chemotherapy. Whether or not the growth of somatic malignancies in such cases is favoured and/ or induced by the therapy remains a matter of speculation. A nephroblastomatous tumor component is encountered in metastases even more often than in primary testicular tumor [5]. The microscopical morphology of testicular teratoma does not differ from those arising in the kidney. The main component of the tumor represents the very indifferent large blastema cells, which easily can be confused with those of embryonal carcinoma. In the more differentiated areas tubular or glomerular structures can be seen. In the spindled cell areas occasionally desmin and myoglobin positive single rhabdomyoblasts can be observed. In some cases the rhabdomyosarcoma component is more aboundant. This skeletal muscle differentiation very typical for nephroblastomas is probably due to the loss of function of the WT -1 gene [5]. Contrary to embryonal carcinoma the indifferent blastema cells are not reactive for cytokeratin antibodies and for CD 30, which is a good marker of embryonal carcinoma. Tubular and glomerular structures however stain positively with cytokeratin antibodies (CAM 5.2). The blastema cells can react with CD 99 (O 13) in about 22% of cases. However, more than 70% of sex cord / gonadal stromal tumors also show a positive reaction with CD 99 [6]. In general chromosomal abnormalities of somatic type tumors arising in teratoma include isochromosome 12 [i(12p)], reflecting germ cell tumor clonality, as well as chromosomal abnormalities associated with the somatic type malignancies (translocations in sarcomas) [7] Also in a recently analysed case of nephroblastoma arisen in teratoma, all germ cell tumor components including nephroblastoma showed the same LOH aberrations suggesting a common clonal origin [5]. References : Eble N et al. ed.: World Health Organisation Classification of Tumours. Pathology & Genetics. Tumours of the Urinary System and Male Genital Organs. IARCPress, LYON 2004 Ulbright TM et al. The development of non germ cell malignancy within germ cell tumors. A clinicopathologic study of 11 cases. Cancer 1984; 54:1824-1833 Ahmed T et al. Teratoma with malignant transformation in germ cell tumors in men. Cancer. 1985 15;56:860-863 Michael H et al. (1997) Primitive neuroectodermal tumors arising in patients with testicular germ cell tumors. J Urol Pathol 9:39-60 Emerson RE et al. Nephroblastoma arising in a germ cell tumor of testicular origin. Am J Surg Pathol. 2004 ;28:687-692 http://www.Immunoquery.com Immunohistochemistry Literature Database Query System Motzer MJ et al. (1998) Teraqtoma with malignant transformation: diverse malignant histologies arising in men with germ cell tumors. J Urol 159: 133-138