Endometrial stromal sarcoma is a rare endometrial tumor arising from the stroma

Stroma (animal tissue)

In animal tissue, stroma refers to the connective, supportive framework of a biological cell, tissue, or organ.The stroma in animal tissue is contrasted with the parenchyma.Examples include:* Stroma of iris...

 (connective tissue) of the endometrium

Endometrium

-Function:The endometrium is the innermost glandular layer and functions as a lining for the uterus, preventing adhesions between the opposed walls of the myometrium, thereby maintaining the patency of the uterine cavity. During the menstrual cycle or estrous cycle, the endometrium grows to a...

 rather than the glands. There are three grades for endometrial stromal tumors, as follows. It was previously known as endolymphatic stromal myosis because of diffuse infiltration of myometrial

Myometrium

The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells , but also of supporting stromal and vascular tissue...

 tissue or the invasion of lymphatic channels .

Endometrial stromal nodule

An endometrial stromal nodule is a noninfiltrative, circumscribed proliferation of endometrial stromal cells. The appearance of the cells is identical to normal stromal cells. This can only be differentiated from low-grade sarcoma by confirming lack of infiltration.

The differential includes cellular leiomyoma

Leiomyoma

A leiomyoma is a benign smooth muscle neoplasm that is not premalignant. They can occur in any organ, but the most common forms occur in the uterus, small bowel and the esophagus.- Etymology:* Greek:** λεῖος leios "smooth"...

. Diagnosis may be aided by immunostaining; endometrial stromal nodules are positive for CD10; leiomyomas are positive for caldesmon

Caldesmon

Caldesmon is a protein that in humans is encoded by the CALD1 gene.Caldesmon is a calmodulin binding protein. Like calponin, caldesmon tonically inhibits the ATPase activity of myosin in smooth muscle....

 and desmin

Desmin

Desmin is a protein that in humans is encoded by the DES gene.Desmin is a type III intermediate filament found near the Z line in sarcomeres. It was first described in 1976, first purified in 1977, the gene was cloned in 1989, and the first knock-out mouse was created in 1996. Desmin is only...

 (and sometimes CD10).

Low-grade endometrial stromal sarcoma

Low-grade endometrial stromal sarcoma consists of cells resembling normal proliferative phase endometrium, but with infiltration or vascular

Vascular

Vascular in zoology and medicine means "related to blood vessels", which are part of the circulatory system. An organ or tissue that is vascularized is heavily endowed with blood vessels and thus richly supplied with blood....

 invasion. These behave more aggressively, sometimes metastasizing, with cancer stage the best predictor of survival. The cells express estrogen/progesterone-receptors.

Undifferentiated uterine sarcoma

Undifferentiated uterine sarcoma, or undifferentiated (high-grade) endometrial stromal sarcoma, does not resemble normal endometrial stroma and behaves much more aggressively, frequently metastasizing. The differential includes leukemia

Leukemia

Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

, lymphoma

Lymphoma

Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...

, high-grade carcinoma

Carcinoma

Carcinoma is the medical term for the most common type of cancer occurring in humans. Put simply, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that generally arises from cells originating in the endodermal or ectodermal germ layer during...

, carcinosarcoma

Carcinosarcoma

Carcinosarcoma is a malignant tumor that is a mixture of carcinoma and sarcoma ....

, and differentiated pure sarcomas.

Cytologic and genetic features

A recurrent chromosomal translocation

Chromosomal translocation

In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer. It is detected on...

, t(7;17)(p15;q21), occurs in endometrial stromal sarcoma. This translocation leads to the fusion of two polycomb

Polycomb-group proteins

Polycomb-group proteins are a family of proteins first discovered in fruit flies that can remodel chromatin such that epigenetic silencing of genes takes place...

 group genes, JAZF1

JAZF1

Juxtaposed with another zinc finger protein 1 also known as TAK1-interacting protein 27 or zinc finger protein 802 is a protein that in humans is encoded by the JAZF1 gene...

 and JJAZ1, with production of a fusion transcript with anti-apoptotic properties. Interestingly, even normal endometrial stroma cells express the fusion gene, derived not by translocation, but by the "stitching" together of m-RNAs

Messenger RNA

Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...

. Thus, it appears that a pro-survival gene in the normal endometrium is somehow subverted to become pro-neoplastic.