Lymph nodes & spleen, nonlymphoma

Ectopic tissue / inclusions

Decidual reaction

Last author update: 1 February 2014
Last staff update: 18 July 2022

Copyright: 2003-2024,, Inc.

PubMed Search: Decidual reaction [title]

Jayalakshmi Balakrishna, M.D.
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Cite this page: Balakrishna J. Decidual reaction. website. Accessed June 16th, 2024.
Definition / general
  • Deposits of decidual tissue without accompanying glands in lymph nodes
  • Rare, incidental microscopic finding in para-aortic and pelvic lymph nodes in pregnancy
  • Decidual cell reaction in the absence of pregnancy is seen only with a corpus luteum present in the ovary
  • Ectopic decidual reaction in lymph nodes was first reported by Geipel in 1913
  • Ectopic decidual reaction can be located in the vagina, cervix, fallopian tubes, ovary, peritoneum; also appendix, diaphragm, liver (surface), lymph nodes, mesentery, small bowel, spleen
  • Rare, but exact incidence unknown since it is detected as an incidental finding at autopsy or pelvic lymphadenectomy for a genital tract malignancy
  • A particular problem differentiating from squamous cell carcinoma during frozen section (Arch Pathol Lab Med 2005;129:e117)
  • Limited to para-aortic and pelvic lymph nodes including obturator and internal iliac lymph nodes
  • Unclear
  • Theories postulated are:
    • Decidual change of endometriotic sites in pregnant women
    • Entrapment of or failure of migration of coelomic remanants during embryologic development and during pregnancy, these rests are sensitized by estrogen, progesterone and further stimuli inducing a decidual reaction
    • Benign metastasis or lymphatic spread
Clinical features
  • May be enlargement of lymph nodes
  • May have associated peritoneal decidual reaction
  • Biopsy of the involved lymph nodes
Prognostic factors
  • Typically no treatment needed
  • Although extremely rare, malignant change can occur in these inclusions
Case reports
Gross description
  • Rarely is grossly visible as tiny, gray, subcapsular nodules
  • Typically occupies the subcapsular sinus and superficial cortex, and less commonly, the central parts of the lymph node
Microscopic (histologic) description
  • Decidual cells arranged in well circumscribed round groups, solid nests and loosely cohesive aggregates in the subcapsular sinus, as well as deep within the lymphoid tissue
  • The individual large polygonal cells show abundant granular esosinophilic cytoplasm, sharply defined cell borders, small, round to oval bland nuclei with dispersed chromatin and single conspicuous nucleoli
  • Mitoses or atypical features are not present
  • The cells may be separated by an intervening amorphous pale staining myxoid stroma
Microscopic (histologic) images

AFIP images


Negative stains
  • Cytokeratins such as CAM5.2 and AE1/AE3 are characteristically negative
Differential diagnosis
  • Metastatic squamous cell carcinoma: small, irregular nests with well circumscribed borders of tightly cohesive, polygonal cells with small, dark staining nuclei and pleomorphism
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