Uterine tumours

Endometrial stromal tumours is like water in the sea - very very common. Many hysterectomies are done for 'em... the most common are leiomyomata (AKA fibroids).

Leiomyomas

General

• Often called "fibroids".
• Extremely common... 40% of women by age 40.
• Benign.
  • Can be a cause of AUB (abnormal uterine bleeding).
  • Large & multiple associated with infertility.

Variants

• Lipoleiomyoma - with adipose tissue.
• Hypercellular leiomyoma - hypercellularity assoc. with more mutations.
• Atypical leiomyoma (AKA symplastic leiomyoma) - leiomyoma with nuclear atypia.
  • Image: Atypical leiomyoma (wikimedia.org).

Gross

• Sharply circumscribed.
• Gray-white.
• Whorled appearance.

Look for...

• Haemorrhage.
• Cystic degeneration.
• Necrosis.

Microscopy

Look for ...

• Necrosis (low power) -- suggestive of leiomyosarcoma.
• Hypercellularity.

IHC

Work-up of suspicious leiomyomas:

• CD10 (+ve).
• Ki-67 (-ve).
• SMA (+ve).
• Desmin (+ve).

Adenomatoid tumour

General:

• Grossly mimics leiomyoma.
• Benign tumour.

Microscopy

Features:

• Contains small tubulocystic spaces lined by cytologically normal mesothelium.

IHC

• CK7 +ve. (???)
• Calretin +ve.

Carcinosarcoma

• AKA "malignant mixed muellerian tumour" (MMMT)
• May have differentiation to:
  • Muscle,
  • Cartilage or
  • Bone.
• Assoc. with previous radiation exposure.
• Metstasize as adenocarcinoma.

Adenosarcoma

Features:

• Benign glands with an abnormal shape.

DDx:

• Benign polyp.

Tx:

• TAH + BSO.

Leiomyocarcoma

General

• Poor prognosis.
• Do not (generally) arise from leiomyomas.
• Often singular, i.e. one tumour; unlike leiomyomas (which are often multiple).

Gross

• "Fleshy" appearance.
• Necrosis.
• Large size.
• Often singular, i.e. one lesion; leiomyomata are often multiple.

Microscopic

1. Cellular atypia - common.
2. Necrosis.
   • Should be patchy/multifocal.
   • Zonal necrosis is suggestive of vascular cause.
3. Mitoses - key feature.
   • 10/HPF.
   • 5/HPF - if epithelioid.
   • 2/HPF - if myxoid.

IHC

• CD10 -ve.
• Positive for SMC markers.
  • Desmin - present in all three types of muscle.
  • Caldesmon.
  • Smooth muscle myosin.

Smooth muscle tumour of uncertain malignant potential (STUMP)

• Like PUNLMP and ASCUS - a waffle category... when one isn't sure it is a leiomyoma vs. leiomyosarcoma.
• Clinical behaviour: usually benign.
• Can be subclassified into four groups - as per Stanford.

Features associated with recurance:

• p16+, p53+, nuclear atypia.

Management

• Long-term follow-up.

Endometrial stromal tumours

Overview

WHO classification:

• Endometrial stromal nodule - not a tumour.
• Endometrial stromal sarcoma (ESS), low grade.
• Undifferentiated endometrial sarcoma

Notes:

• Some believe in a "high grade ESS"... some don't.

Low grade endometrial stromal sarcoma

Features:

• Highly cellular Islands with a wavy irregular border.
  • Border has finger-like projections/tongue-like projections.
  • Benign uterine smooth muscle between islands of tumour cells.
• Epithelioid cells.
• High NC ratio.
• Thin blood vessels within islands of cells.
  • Tumour cells pallisade around the vessels.

Notes:

• Vaguely resembles the stroma of proliferative endometrium.

Undifferentiated endometrial sarcoma

Features:

1. Marked nuclear atypia.
2. Mitoses+++.
3. Poorly differentiated - key feature
   • Looks nothing like low grade endometrial stromal sarcoma.
   • Negative for smooth muscle markers (to exclude leiomyosarcoma).

Notes:

• Need IHC to diagnose.

DDx:

• Leiomyosarcoma.
• Carcinosarcoma.
• Rhabdomyosarcoma.
• Melanoma.