Confusable diagnoses · PANCE / PANRE

Endometriosis vs Uterine Fibroids

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Endometriosis and Uterine Fibroids are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Endometriosis vs Uterine Fibroids at a glance

  • Endometriosis: Ectopic endometrial-like tissue causing cyclic pelvic pain, dysmenorrhea, dyspareunia, and infertility.
  • Uterine Fibroids: Benign smooth-muscle tumors of the myometrium causing heavy bleeding, bulk symptoms, and reproductive complications.

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Question 1ReproductiveMedium
A 25-year-old woman has had severe dysmenorrhea, dyspareunia, and infertility for 2 years. Pelvic ultrasound is normal. The CA-125 is mildly elevated at 68 U/mL. Which of the following is the most appropriate next step to confirm the diagnosis?
  • AHysterosalpingography with contrast
  • BContrast-enhanced pelvic MRI scan
  • CDiagnostic laparoscopy with biopsy
  • DHysteroscopy with endometrial biopsy
Reveal answer & full explanation
Correct answer: C — Diagnostic laparoscopy with biopsy
  • AHysterosalpingography with contrast
  • BContrast-enhanced pelvic MRI scan
  • CDiagnostic laparoscopy with biopsy✓
  • DHysteroscopy with endometrial biopsy

Why Diagnostic laparoscopy with biopsy is correct

  • The triad of severe dysmenorrhea, dyspareunia, and infertility with a normal ultrasound points to endometriosis, often with peritoneal implants that imaging misses.
  • Because the lead-in asks how to CONFIRM the diagnosis, laparoscopy with direct visualization and histologic biopsy is the diagnostic gold standard, providing tissue confirmation.
  • CA-125 is nonspecific (also elevated in pelvic inflammatory disease, fibroids, and malignancy) and cannot confirm endometriosis.

Why the others are wrong

  • Hysterosalpingography with contrast — outlines the uterine cavity and tubal patency in an infertility workup but cannot visualize peritoneal implants, so the diagnosis remains unconfirmed whatever it shows. Sets the infertility-workup-reflex trap.
  • Contrast-enhanced pelvic MRI scan — helps map deep infiltrating disease before surgery but does not provide the tissue diagnosis the question asks for. Sets the imaging-instead-of-tissue trap.
  • Hysteroscopy with endometrial biopsy — samples eutopic endometrium inside the uterine cavity, whereas endometriosis is by definition implants outside it, so the histology would be normal. Sets the right-procedure-wrong-compartment trap.
Question 2ReproductiveMedium
A 42-year-old G3P3 woman reports 8 months of progressively heavier menstrual periods, now soaking a pad every 2 hours and passing clots, along with pelvic fullness and urinary frequency. She has no intermenstrual or postcoital bleeding, and vital signs are normal. On bimanual examination the uterus is enlarged to a 14-week size, firm, irregularly contoured, and nontender, with no adnexal masses. Hemoglobin is 9.6 g/dL with a low ferritin, and a urine pregnancy test is negative. Transvaginal ultrasound shows several well-circumscribed hypoechoic myometrial masses distorting the uterine contour. Which of the following is the most likely diagnosis?
  • AEndometrial cancer
  • BEndometrial polyp
  • CUterine adenomyosis
  • DUterine leiomyoma
Reveal answer & full explanation
Correct answer: D — Uterine leiomyoma
  • AEndometrial cancer
  • BEndometrial polyp
  • CUterine adenomyosis
  • DUterine leiomyoma✓

Why Uterine leiomyoma is correct

  • The classic picture is a premenopausal woman with heavy menstrual bleeding, iron-deficiency anemia (Hgb 9.6 g/dL, low ferritin), and an enlarged, firm, irregularly contoured, NONTENDER uterus sized in gestational weeks.
  • Bulk symptoms such as pelvic fullness and urinary frequency reflect mass effect from anterior fibroids on the bladder; heavy bleeding arises from distorted endometrial vasculature and impaired hemostasis.
  • Transvaginal ultrasound is first-line and here shows the characteristic well-circumscribed hypoechoic myometrial masses distorting the uterine contour. Fibroids are estrogen- and progesterone-responsive and grow during the reproductive years.

Why the others are wrong

  • Uterine adenomyosis — diffuse invasion of endometrial glands into the myometrium causing heavy, PAINFUL menses with a diffusely enlarged, boggy, TENDER uterus and a widened junctional zone on MRI; this uterus is firm, irregular, and nontender, and ultrasound shows discrete masses rather than diffuse enlargement.
  • Endometrial polyp — typically causes intermenstrual or postcoital spotting with a normal-sized uterus and is diagnosed by saline-infusion sonohysterography or hysteroscopy; it does not produce an enlarged irregular uterus, bulk symptoms, or discrete myometrial masses.
  • Endometrial cancer — suggested by postmenopausal or atypical bleeding and warrants endometrial biopsy in at-risk patients, but it arises in the endometrium and would not present as multiple well-circumscribed myometrial masses; the cyclic heavy menses, low ferritin, and characteristic myometrial sonographic findings here point to fibroids.
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Side-by-side comparison

FeatureEndometriosisUterine Fibroids
At a glanceEctopic endometrial-like tissue causing cyclic pelvic pain, dysmenorrhea, dyspareunia, and infertility.Benign smooth-muscle tumors of the myometrium causing heavy bleeding, bulk symptoms, and reproductive complications.
Classic presentationReproductive-age woman with progressive secondary dysmenorrhea, deep dyspareunia, and infertility; ovarian 'chocolate cyst' on ultrasound.; Cyclic pelvic pain that worsens with menses (secondary dysmenorrhea); Deep dyspareunia; Dyschezia, cyclic rectal bleeding, or dysuria (depending on implant location); Infertility (often the…Premenopausal woman with heavy menses, iron-deficiency anemia, and an enlarged irregular uterus.; Heavy menstrual bleeding (most common); prolonged or intermenstrual bleeding; Pelvic pressure or fullness, bloating, increased abdominal girth; Urinary frequency or hesitancy (anterior fibroids on bladder); Constipation or tenesmus…
Workup / key labsHistorically definitive diagnosis required laparoscopic visualization with histologic confirmation; current ACOG/ESHRE guidance supports clinical diagnosis and empiric treatment when imaging and history are consistent, reserving surgery for refractory cases or when histology will change management. When confirmation is needed (negative…CBC (iron-deficiency anemia common), ferritin; TSH, prolactin if irregular bleeding; Pregnancy test; Endometrial biopsy if age ≥45, risk factors for hyperplasia, or persistent abnormal bleeding
ImagingTransvaginal ultrasound — first-line; identifies endometriomas (homogeneous low-level echoes, 'ground glass' appearance) and deep infiltrating disease; MRI — for surgical planning, deep infiltrating endometriosis, or extra-pelvic disease; Empiric medical therapy may be initiated without surgical confirmation if clinical picture is…Transvaginal ultrasound — first-line; characterizes size, number, location; Saline-infusion sonohysterography or hysteroscopy — best for submucosal fibroids and cavity distortion; MRI — pre-operative mapping, suspected adenomyosis, or assessment before uterine artery embolization
First-line treatmentNSAIDs — ibuprofen, naproxen — for pain; Combined hormonal contraception (COCP, patch, ring) — continuous or cyclic; first-line hormonal therapy; Progestins — norethindrone acetate, medroxyprogesterone, dienogest, levonorgestrel 52 mg IUDExpectant management for asymptomatic fibroids; NSAIDs for dysmenorrhea; Tranexamic acid 1.3 g TID × up to 5 days per cycle for heavy bleeding; Combined hormonal contraception or progestin-only options for bleeding control; Levonorgestrel IUD — effective for heavy menstrual bleeding when cavity not significantly distorted; Iron…

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Full outlines

Endometriosis Uterine Fibroids (Leiomyoma) All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.