A 58 year-old female with a several-year history of pelvic pain and menometrorrhagia undergoes hysterectomy. Gross examination of the uterus reveals several rubbery white masses with a whorled appearance.

A biopsy is performed, and representative sections are shown here.

What is this lesion?

A. Leiomyoma
B. Leiomyosarcoma
C. Endometrial carcinoma
D. Cervical carcinoma
E. Fibroma

(Scroll down for the answer)

The diagnosis in this case is leiomyoma. If you have spent any time in the gross room (where we cut open specimens), you have seen about 1,000 of these. In fact, the question might have seemed tricky because the diagnosis was too obvious to be true! For readers who haven’t spent much time in a pathology lab, and for the sake of review for those of us who have, let’s talk a bit about leiomyomas.

Some sources say that leiomyomas are the most common tumor in women. That certainly seems like an accurate statement. You can tell what they are (and whether they are benign or malignant) just by reading the name: leio (smooth) myo (muscle) oma (benign tumor). Totally benign, and composed of smooth muscle, leiomyomas occur predominantly in the uterine wall. They may occur singly or in multiple locations within the uterus. Usually, these tumors produce no symptoms, but occasionally, they cause bleeding, pain, or infertility.

Leiomyomas are frequently referred to as “fibroids,” which is a misnomer since they are composed of smooth muscle, not fibrous tissue. Histologically, the tumor has a uniform appearance, with bundles of smooth muscle cells resembling those of the normal myometrium. The tumor cells are spindle shaped, and mitotic figures are rare.

Some variants of leiomyoma have more pleomorphic cells. However, the mitotic index always remains low. Fortunately, malignant transformation is vanishingly rare.

If you liked this case, and want to test yourself with other unknown cases, here are some to try:

• Case 1: 20-year-old male who died suddenly
• Case 2: 72-year-old male with right calf mass
• Case 3: 67-year-old female with pancytopenia
• Case 4: 59-year-old male with severe headaches
• Case 5: 38-year-old female with deep venous thrombi
• Case 6: 13-year-old male with cerebellar mass
• Case 7: 45-year-old male with pulmonary emphysema
• Case 8: 38-year-old male with AIDS and headaches
• Case 9: 25-year-old male with arm mass
• Case 10: 57-year-old male with fatigue and left upper quadrant heaviness
• Case 11: 62-year-old male with hepatosplenomegaly, skin lesions and cardiomyopathy
• Case 12: 16-month-old infant with failure to thrive
• Case 13: 36-year-old female with painless lower leg nodule