Hypodermal decidualized endometrioma with aberrant cytokeratin expression. A lesion mimicking malignancy

Our plain-English summary of Hypodermal decidualized endometrioma with aberrant cytokeratin expression. A lesion mimicking malignancy, by J.F. Val-Bernal, D. Val, F. Gómez-Aguado, et al (The American Journal of Dermatopathology, 2011).

The study

• Authors: J.F. Val-Bernal, D. Val, F. Gómez-Aguado, M.T. Corcuera, M.F. Garijo
• Journal: The American Journal of Dermatopathology
• Published: 2011;33(5):e58-62
• Type of article: Case report
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Decidualized endometrioma is a pseudoneoplastic lesion that may appear as a solitary nodule in the hypodermis, simulate a malignant epithelioid tumor, and can represent a diagnostic challenge. A 36-year-old woman delivered a full-term baby by cesarean. At the immediate puerperium, she complained of a subcutaneous nodule measuring 2.5 cm, underneath a previous caesarean scar from the former full-term delivery 3 years earlier. Histologic features included a nodular growth pattern of large monomorphic epithelioid cells showing diffuse positivity for cytokeratin (AE1/AE3, 18), human placental lactogen, and CD10 and focal positivity for inhibin alpha. The main differential diagnoses include trophoblastic neoplasia and deciduoid mesothelioma. Good clinicopathological correlation is essential for the correct diagnosis. Immunohistochemical stains can be misleading. An important clue is the combination of large decidualized cells and lumens lined by flat or low cuboidal cells that are atrophic endometrial glands. This lesion has a benign behavior.

In plain English

This was a case report about one patient, a 36-year-old woman. Right after a caesarean delivery, she reported a 2.5 cm nodule under the skin beneath the scar from an earlier caesarean delivery 3 years before. The nodule was removed. Under the microscope, it was made of large, fairly uniform cells. These cells stained positive for pancytokeratin (AE1/AE3), cytokeratin 18, human placental lactogen and CD10, and in places for inhibin-alpha. They were negative for markers including calretinin and cytokeratin 5/6. The authors wrote that this staining pattern at first suggested a trophoblastic tumor. However, a few small glands lined by flat or cuboidal cells, together with electron microscopy, fit a decidualized endometrioma: a non-cancerous mass of misplaced endometrial tissue showing decidual change. They named trophoblastic neoplasia and deciduoid mesothelioma as the main conditions it could be mistaken for. The patient was well 5 months after surgery. The authors concluded that this lesion can mimic cancer, that immunohistochemical stains can be misleading, and that the lesion behaves benignly. The article did not study asbestos exposure.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (single patient)
• Who was studied: One 36-year-old woman (gravida 2, para 2) with a 2.5 cm nodule under the skin beneath a previous caesarean scar, treated in Spain (Santander and Madrid hospitals); no dates given
• Exposure: Not applicable: the article did not study asbestos or any other exposure, and did not report the patient's asbestos exposure
• Main results:
  • The removed nodule was well circumscribed, firm, lobulated and white, measuring 2.1 by 2.0 by 1.5 cm
  • The large cells showed diffuse positivity for pancytokeratin (AE1/AE3), cytokeratin 18, human placental lactogen and CD10, and focal positivity for inhibin-alpha
  • The large cells were negative for epithelial membrane antigen, placental alkaline phosphatase, beta-hCG, p63, cytokeratin 5/6 and calretinin
  • The Ki-67 labeling index of the lesion was 19%
  • Flat or cuboidal cells lining small lumens (endometrial glands) stained for AE1/AE3, CK18 and epithelial membrane antigen, showing two cell populations (glandular and stromal)
  • The authors reported that the antibody panel initially suggested an intermediate trophoblastic tumor
  • Electron microscopy showed features consistent with decidual cells
  • The main differential diagnoses the authors considered were trophoblastic neoplasia and deciduoid (pseudodecidual) mesothelioma
  • After surgery, the patient's serum CA-15.3 was elevated (99.9 U/mL); beta-hCG, alpha-fetoprotein and CA-125 were normal
  • The patient remained well 5 months after removal of the nodule
• The authors' conclusion: The authors concluded that decidualized endometrioma can mimic a malignant tumor, that clinical and pathological features are essential for diagnosis, that immunohistochemical stains can be misleading, and that the lesion behaves benignly

Topics

Medical terms in this study, explained in our Lexicon: Epithelioid, Mesothelioma.

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