**1. Introduction**

Endometriosis is a chronic debilitating inflammatory disease of women, with the growth of ectopic endometrium in extrauterine sites like uterosacral ligaments, pelvic peritoneum, rectovaginal septum, other peritoneal surfaces, ovaries, etc. It is an extremely heterogeneous clinical entity as regards etiopathogenesis, clinical features, and treatment. The genetic basis of this disease has been quite clear and endometriosis running in families has been quite established. The exact etiopathogenesis and treatment option of the disease is still evolving. Though endometriosis is not regarded as a malignant disorder, it does have some features akin to malignant disease. They are local and distant metastasis, invasion and destruction of adjacent structures, unrestricted growth, resistance to apoptosis, development of new blood vessels etc [1]. With the increasing availability of new gene sequencing methods, the genetic profiling of endometriosis has given way to new findings that endometriosis and certain cancers share the same aberrant genetic sequences.

Sampson et al. in 1925 postulated a histological link between endometriosis and cancer and proposed the three criteria for the diagnosis of endometriosis-associated ovarian cancer (EAOC). They were (1) evidence of endometriosis close to the tumor, (2) exclusion of invasion from other sources, (3) presence of tissue resembling endometrial stroma surrounding characteristic epithelial glands [2]. Scott et al. in 1953 revised the criteria and added the fourth criterion, i.e., histological proof of transition from benign changes in endometriosis to malignant changes [3].

#### **Figure 1.**

*(a) Cut section of an ovarian mass showing chocolate material with solid components, (b) clear cell carcinoma ovary associated with endometriosis, (c) endometrioid adenocarcinoma in the vicinity of endometriosis.*

All four criteria are continued in practice to diagnose endometriosis-associated malignancy (EAM) (**Figure 1**).

Endometriosis is associated with genetic instability and several genetic alterations. Loss of heterozygosity (LOH) at 10q23, PTEN, ARID1A, and p53 mutations have been found in both endometriosis and EAM [4]. It is presumed that EAM arises from atypical endometriosis, which is an intermediate lesion between endometriosis and cancer. About 80% of EAM is found in the ovary and the rest are localized in the abdominal wall, pleura, intestine, rectovaginal septum etc [5].

Considering the above facts, obvious controversies ensue as to the role of endometriosis as the cause of malignant transformation or a mere association with cancers.
