**Core Concept**
Testicular carcinoma can be broadly classified into two main categories: germ cell tumors (GCTs) and non-germ cell tumors (NGCTs). Germ cell tumors arise from the germ cells of the testis, whereas non-germ cell tumors originate from the supporting cells of the testis, such as Sertoli or Leydig cells.

**Why the Correct Answer is Right**
Seminomas and non-seminomatous germ cell tumors (NSGCTs) are the two main types of germ cell tumors, accounting for the majority of testicular cancers. However, other types of testicular carcinomas, such as sex cord-stromal tumors (e.g., Sertoli cell tumors, Leydig cell tumors) and embryonal carcinomas, are not germ cell tumors. These non-germ cell tumors arise from the supportive cells of the testis and have distinct histological and biological characteristics.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because seminomas are a type of germ cell tumor. They are the most common type of testicular cancer and are characterized by their uniform, round, and large cells.
**Option B:** This option is incorrect because non-seminomatous germ cell tumors (NSGCTs) are also a type of germ cell tumor. They are a heterogeneous group of tumors that include embryonal carcinoma, yolk sac tumor, choriocarcinoma, and teratoma.
**Option C:** This option is incorrect because embryonal carcinoma is a type of non-seminomatous germ cell tumor, which is a germ cell tumor.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that testicular carcinoma can be broadly classified into two main categories: germ cell tumors and non-germ cell tumors. This distinction is crucial for accurate diagnosis and treatment planning.

**Correct Answer:** D.