**Question:** Not an epithelial cancer of ovary -

A. Ovarian germ cell tumor
B. Ovarian stromal cell tumor
C. Ovarian endometriosis
D. Ovarian mature teratoma

**Correct Answer:** B. Ovarian stromal cell tumor

**Core Concept:**

Ovarian neoplasms are a diverse group of tumors that originate from various cell types in the ovary. The most common types include epithelial cancers, germ cell tumors, stromal cell tumors, and surface epithelial-stromal tumors (Sertoli-Leydig cell tumors). These neoplasms can be broadly categorized into benign, borderline, and malignant.

**Why the Correct Answer is Right:**

Ovarian stromal cell tumors are a subgroup of ovarian neoplasms that arise from the stromal cells of the ovary. They are classified into benign, borderline, and malignant categories, similar to epithelial cancers and germ cell tumors. However, in this question, we are focusing on the malignant variant.

**Why Each Wrong Option is Incorrect:**

A. Ovarian germ cell tumors (GCTs) are another type of ovarian neoplasm that arises from germ cells and includes yolk sac tumors, dysgerminomas, and non-seminomatous germ cell tumors.
B. Ovarian stromal cell tumors are not the same as epithelial cancers, which are primarily composed of cells derived from the ovarian surface epithelium.
C. Ovarian endometriosis is a benign condition characterized by the presence of endometrial tissue outside the uterus, while the question is about malignant ovarian neoplasms.
D. Ovarian mature teratomas are germ cell tumors composed of tissues derived from all three embryonic germ cell layers, not stromal cell tumors.

**Clinical Pearl:**

A thorough understanding of the various types of ovarian neoplasms is crucial for accurate diagnosis and treatment planning. Recognizing the differences between epithelial cancers, germ cell tumors, stromal cell tumors, and endometriosis is essential for medical students and practicing physicians alike.