Stromal tumors
Endometrial stromal nodule

Topic Completed: 1 August 2011

Minor changes: 2 April 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed search: endometrial stromal nodule

Mohamed Mokhtar Desouki, M.D., Ph.D.
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Cite this page: Desouki M. Endometrial stromal nodule. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/uterusstromalnodule.html. Accessed May 16th, 2021.
Definition / general
  • Benign tumor composed of cells reminiscent of proliferative phase endometrial stroma
  • Occur at any age during reproductive or later years (mostly in the fifth and sixth decades)
Clinical features
  • May present with abnormal uterine bleeding, but most tumors are incidental findings in a hysterectomy specimen
  • Prognostic significance of limited infiltration is unclear (Am J Surg Pathol 2002;26:567)
  • Excellent prognosis; patients are cured by hysterectomy
  • Conservative excision may be adequate, but usually limits ability to sample margins
Gross description
  • Classically round, soft, yellow, solitary, sharply circumscribed neoplasm, confined to uterus, with no intravascular component
  • Tumors are not encapsulated; they are usually solitary, ranging from 1 to 22 cm
  • If located in endometrium, they are frequently polypoid
  • Tumors may be located intramurally with no connection to the surface endometrium
  • No whorled pattern characteristic of a leiomyoma
  • Cysts may be present
  • Tumors grow in an expansile, non-infiltrating pattern with a smooth margin
Microscopic (histologic) description
  • Usually uniformly well circumscribed, monotonous proliferations of bland endometrial stromal cells
  • Expansive growth pattern (not infiltration) at margin
  • Infiltration, if present, should be at most one to three protrusions, 3 mm or less
  • Usually prominent arterioles
  • May have sex cord-like differentiation or infarct-like necrosis
  • No angiolymphatic invasion, minimal mitotic activity (< 10 per 10 HPF)
  • Note: foci of smooth muscle metaplasia within the tumor should NOT be interpreted as myometrial invasion at the edge of the tumor
Microscopic (histologic) images

AFIP images

Circumscription with pushing margin

Cells resemble those of proliferative phase endometrial stroma

Regularly distributed small blood vessels

Thick bands of hyalinized collagen

Starburst pattern of hyalinized collagen

Numerous cells with foamy cytoplasm

Note large focus of smooth muscle differentiation

Reticulin fibers wrapping around individual tumor cells

Negative stains
Differential diagnosis
Additional references
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