Thecomas or theca cell tumors are benign

Benign

A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...

 ovarian neoplasm

Ovarian cancer

Ovarian cancer is a cancerous growth arising from the ovary. Symptoms are frequently very subtle early on and may include: bloating, pelvic pain, difficulty eating and frequent urination, and are easily confused with other illnesses....

s composed only of theca cells. Histogenetically they are classified as sex cord-stromal tumour

Sex cord-stromal tumour

Sex cord-gonadal stromal tumour is a group of tumours of sex cord-derived tissues of the ovary and testis. In humans, this group accounts for 8% of ovarian cancers and under 5% of testicular cancers. Their diagnosis is histological: only a biopsy of the tumour can make an exact diagnosis...

s.

They are typically estrogen

Estrogen

Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...

-producing and they occur in older women (mean age 59; 84% after menopause

Menopause

Menopause is a term used to describe the permanent cessation of the primary functions of the human ovaries: the ripening and release of ova and the release of hormones that cause both the creation of the uterine lining and the subsequent shedding of the uterine lining...

). (They can, however, appear before menopause.)

Sixty percent of patients present with abnormal uterine bleeding, and 20% have endometrial carcinoma.

Pathologic features

Grossly, the tumour is solid and yellow.

Grossly and microscopically, it compress of the ovarian cortex.

Microscopically, the tumour cells have abundant lipid

Lipid

Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

-filled cytoplasm

Cytoplasm

The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

.