**15. Common problems in the differential diagnosis of endometriosis**

In the ovary, the presence of hemorrhagic follicle cysts or cystic corpora lutea may cause diagnostic problems, although the presence of granular layer cells or luteinized cells aid to the diagnosis. Serosal inclusion cysts lined by serous cells are diagnosed as such because of the absence of a stromal component and associated alterations. Rete ovarii present a characteristic ramifying pattern and absence of stromal cells and hemorrhage. Mesonephric and paramesonephric remnants are surrounded by smooth muscle and are lined with low cuboidal epithelium. Dermoid cysts may be lined by macrophages and granulation tissue but in multiple sections squamous cells and hair fragments will be observed. It must be noted that there are cases that the laparoscopic picture is diagnostic but the typical picture of endometriosis cannot be established and only stromal cells and other changes such as hemorrhage and macrophages are observed. In these cases the most appropriate diagnosis is that the lesion is "compatible with endometriosis".

#### **16. Metaplastic and hyperplastic glandular changes observed in endometriosis**

The glandular cells of endometriosis may present metaplastic changes such as ciliated, eosinophilic, clear cell and rarely squamous, transitional and rarely mucinous metaplasia

Typically endometriosis in women of reproductive age presents histologically as one or more endometrioid glands surrounded by stromal cells, resembling the endometrial stromal cells of the proliferative phase. The glandular epithelium is one layer thick with cuboidal or tall cells and eosinophilic cytoplasm. Nuclei are ovoid with vertical orientation and very rare mitoses. The whole picture is usually consistent with inactive or irregular proliferative endometrium, although typical proliferative or secretory changes may be observed. Cilia may be observed as well. Stromal cells are supported by a delicate reticulin network in which hyperemic small vessels may be observed. In the case of exogenous administration of progestins, cyclically functionic endometriosis or pregnancy, a stromal decidual reaction may be observed. A diffuse infiltration of histiocytes is usually observed. The histiocytes convert the red blood cells into glucolipid and brown pigment (pseudoxanthoma cells) .The pigment is usual a ceroid such as lipofuscin and to a lesser extend hemosiderin .The amount of the pigment increases with the age of the lesion. Inflammatory cells may be present and a small component of smooth muscle cells especially in the wall of endometrioid cysts may be observed. Not all the above described elements are easily identified in endometriosis. Especially in the cases of ovarian endometrioid cysts the lesion appears to be composed of stroma, with fibrosis, lined by hemosiderin-laden macrophages. Many histological sections may be necessary to identify the glandular component of endometriosis. One must keep in mind that macrophages may be connected with hemorrhagic follicles or corpora lutea and only the presence of glandular epithelium or luteinized cells is diagnostic. The degree of cyclic changes of the glandular component depend on the amount of fibrous tissue, the amount of stroma round the glands, the degree of vascularity and the steroid receptor content Endometriosis in places with native smooth muscle component may induce marked hypertrophy identical to that observed in cases of adenomyosis that leads to creation of

**14. Microscopic features of endometriosis** 

adenomyomata or adenomyomatous nodules (Anaf et al, 2000).

that the lesion is "compatible with endometriosis".

**endometriosis** 

**15. Common problems in the differential diagnosis of endometriosis** 

**16. Metaplastic and hyperplastic glandular changes observed in** 

In the ovary, the presence of hemorrhagic follicle cysts or cystic corpora lutea may cause diagnostic problems, although the presence of granular layer cells or luteinized cells aid to the diagnosis. Serosal inclusion cysts lined by serous cells are diagnosed as such because of the absence of a stromal component and associated alterations. Rete ovarii present a characteristic ramifying pattern and absence of stromal cells and hemorrhage. Mesonephric and paramesonephric remnants are surrounded by smooth muscle and are lined with low cuboidal epithelium. Dermoid cysts may be lined by macrophages and granulation tissue but in multiple sections squamous cells and hair fragments will be observed. It must be noted that there are cases that the laparoscopic picture is diagnostic but the typical picture of endometriosis cannot be established and only stromal cells and other changes such as hemorrhage and macrophages are observed. In these cases the most appropriate diagnosis is

The glandular cells of endometriosis may present metaplastic changes such as ciliated, eosinophilic, clear cell and rarely squamous, transitional and rarely mucinous metaplasia usually of endocervical type. It is reported that in cases with extensive metaplastic changes in endometriosis an association with an ovarian epithelial tumor is observed. Glandular epithelium may present hyperplastic changes due to endogenous or exogenous hormonal action resembling hyperplastic endometrial changes from simple cystic to complex atypical hyperplasia. In cases of ovarian endometrioid adenocarcinoma remnants of endometriosis with hyperplastic changes are observed. Metaplastic changes are observed in the endometriotic stroma as well, of smooth muscle type. Concomitant hyperplastic changes may create endomyometriotic nodules or uterus–like masses, in the ovary, broad ligament, the bowel and lymph nodes.
