Frank Hinman 



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maturity. Any complete classification, of course, must include the rare tumors 

 of Ewing's groups 1 and 4. All tumors in his groups 2 and 3, however, can be 

 listed as follows under parenchymatous tumors arising in a teratoma. 



a. Embryonal carcinoma without lymphoid stroma 



b. Embryonal carcinoma with lymphoid stroma 



c. Large clear-cell carcinoma 



d. Embryonal adenocarcinoma 



e. Chorionepithelioma 



The most common and probably least malignant tumor of the testis is the 

 embryonal carcinoma, of which there are two types. Usually this is a mono- 

 cellular tumor of rapid growth (the seminoma of Chevassu). 



a. The embryonal carcinoma without lymphoid stroma is a tumor with 

 well-differentiated cells resembling adult seminal epithelium. In the micro- 

 scope large, pale, round or polyhedral cells of uniform size are seen lying in 

 a light fibrous stroma containing few lymphoid cells. Occasionally an alveolar 

 arrangement is observed. Many mitotic figures are present. This tumor is 

 relatively rare. 



b. The embryonal carcinoma with lymphoid stroma is the most common 

 tumor of the testis. It also is made up of well-differentiated cells. By the micro- 

 scope small dark-staining cells, usually in sheets, are seen lying in an abundant 

 lymphoid stroma composed of immature fibroblasts. 



c. The large clear-cell carcinoma is made up of less well-differentiated cells 

 than those found in the foregoing tumors. It is probably more malignant. 

 Microscopically, closely packed large cells with relatively large pale nuclei 

 containing dark nucleoli, are grouped in a light fibrous stroma. They resemble 

 somewhat the Langhans type of cell. This tumor is uncommon. 



d. The embryonal adenocarcinoma occurs in two varieties which are not 

 easily distinguished: 



1. The adenocarcinoma, made up of primitive cells, is relatively rare. The 

 characterizing embryonal cell is large, producing a moderate amount of 

 cytoplasm and having a finely divided chromatin. Clinical follow-up of pa- 

 tients with this type of tumor, however, has shown a high degree of malig- 

 nancy and in two cases particidarly Carr recognized definite transitional stages 

 between adenocarcinoma and chorionepithelioma. 



2. The more differentiated type of embryonal adenocarcinoma occurs next 

 in frequency to the embryonal carcinoma with lymphoid stroma. The mic- 

 roscopic appearance is similar to that seen in adenocarcinoma of other epi- 

 thelial structures. 



e. Chorionepithelioma is the most primitive and the most malignant of the 

 testicular tumors. Microscopically it is made up of large undifferentiated types 

 of cell and the characteristic multinuclear syncytial cells are found. Judging 

 from the literature, this tumor is rare, but of the last forty-four cases of tumor 

 of the testis seen here six were chorionepitheliomata. In two of these the pri- 

 mary tumor showed no chorionic elements, but the clinical course and the rise 



