Pregnancy Deciduosis Mimicking Abdominal Tuberculosis and Peritoneal Carcinomatosis: A Case Report

Our plain-English summary of Pregnancy Deciduosis Mimicking Abdominal Tuberculosis and Peritoneal Carcinomatosis: A Case Report, by A. Musarò, M.P. Bonasoni, M. Pati, et al (Diagnostics, 2026).

The study

• Authors: A. Musarò, M.P. Bonasoni, M. Pati, E. Carossino, A. Ferretti, B. Petrachi, A. Cavazza, A. Papapietro, I. Tamagnini, M. Marchetti, L. Aguzzoli
• Journal: Diagnostics
• Published: 2026;16(18)
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Background and clinical significance: Gestational deciduosis is a benign, progesterone-related ectopic decidual reaction that commonly involves pelvic and peritoneal surfaces and usually regresses after delivery. Although generally asymptomatic, diffuse peritoneal deciduosis may present as multiple nodular implants and closely mimic peritoneal carcinomatosis, mesothelioma, or miliary tuberculosis, creating a challenging intraoperative differential diagnosis. Prompt histopathological assessment is essential to prevent unnecessary staging procedures or oncological treatment. Case presentation: A 30-year-old primigravida at 40 weeks' gestation underwent unplanned intrapartum cesarean section after a premature rupture of membranes, the induction of labor, and failed progression. Multiple friable, gray-yellow subcentimetric nodules were incidentally observed on the uterine serosa, adnexa, omentum, visceral intestinal peritoneum, and appendix. The macroscopic appearance raised concern for peritoneal carcinomatosis and abdominal miliary tuberculosis. No ascites or intra-abdominal masses were identified. CA-125 was elevated (207.7 U/mL), Quantiferon testing was indeterminate, and postoperative chest computed tomography showed no pulmonary disease. Histological examination showed ectopic decidual cells with abundant eosinophilic cytoplasm in a perivascular and septal distribution. The cells showed diffuse vimentin, CD10, and progesterone-receptor expression and lacked epithelial and mesothelial marker expression, supporting diffuse peritoneal deciduosis. The postoperative course was uncomplicated, and pelvic ultrasonography at 40 days postpartum showed no residual lesions. Conclusions: Diffuse peritoneal deciduosis should be considered when disseminated peritoneal nodules are encountered during pregnancy or cesarean delivery. In this setting, elevated CA-125 is nonspecific and may heighten concern for tuberculosis or malignancy without distinguishing among these entities. Correlation of the clinical context, operative findings, morphology, and targeted immunohistochemistry is essential to avoid unnecessary oncological treatment or extensive staging procedures.

In plain English

This case report from a hospital in Reggio Emilia, Italy, described one woman, aged 30 and in her first pregnancy, who had an unplanned cesarean delivery at 40 weeks. During the operation, surgeons unexpectedly found many small grayish-yellow nodules on the uterine surface, adnexa, omentum, bowel surface and appendix. These raised concern for peritoneal carcinomatosis (cancer spread across the abdominal lining) and abdominal tuberculosis. Her CA-125 blood marker was elevated at 207.7 U/mL, a Quantiferon tuberculosis test was indeterminate, and a chest CT showed no lung disease. Microscopy and special stains showed benign decidual cells, a progesterone-related pregnancy change called diffuse peritoneal deciduosis. Most markers used to identify mesothelioma or carcinoma were negative, although WT1, usually reported negative in deciduosis, was positive. At 40 days after delivery, ultrasound showed no remaining lesions. The authors concluded that this benign condition may closely mimic miliary tuberculosis or peritoneal carcinomatosis, and that the CA-125 value could not tell these apart. Mesothelioma appears only as a disease these nodules can resemble. The article does not discuss asbestos.

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 30-year-old woman in her first pregnancy, at 40 weeks of gestation, treated at Azienda USL-IRCCS di Reggio Emilia, Italy (date of care not stated)
• Exposure: No asbestos or fiber exposure is studied or mentioned. The condition reported is a pregnancy-associated (progesterone-related) change, not an occupational or environmental exposure.
• Main results:
  • During the cesarean section, nodules were found on the uterine serosa, adnexa, omentum, intestinal visceral peritoneum and appendix of this patient.
  • The patient's CA-125 was elevated at 207.7 U/mL (reference below 30 U/mL).
  • The Quantiferon test was indeterminate, and the postoperative chest CT showed no lung involvement.
  • Biopsies showed benign ectopic decidua: large polyhedral cells with eosinophilic cytoplasm and round nuclei.
  • The cells were positive for vimentin (strong, diffuse) and WT1 (nuclear), and positive for PR (strong, diffuse), with focal ER.
  • The cells were negative for CKAE1/AE3, CK5, calretinin, S100, SMA, HMB45, PAX8 and BerEP4.
  • WT1 positivity in this case differed from the negative WT1 generally reported in deciduosis.
  • The patient went home on postoperative day three. At 40 days postpartum, pelvic ultrasound showed no residual lesions.
• The authors' conclusion: The authors concluded that diffuse gestational deciduosis is rare and benign but may closely mimic miliary tuberculosis or peritoneal carcinomatosis. They also concluded that the CA-125 value in this case could not distinguish deciduosis from peritoneal tuberculosis or carcinomatosis.
• Limitations the authors state:
  • The case cannot establish a causal link between the patient's hyperemesis gravidarum, progesterone levels and the deciduosis.
  • The precise mechanism of the CA-125 elevation could not be determined.
  • The diagnostic schematic in Figure 3 is educational only and has not been prospectively developed or validated.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Differential Diagnosis, Staging, Friable, Omentum, Peritoneum, Ascites, CA-125.

Related studies

• Peritoneal deciduosis mimicking peritoneal Carcinomatosis: A case report — J. Casanova, J. Jurgiel, et al. (2021)
• Pregnancy-related peritoneal ectopic decidua (deciduosis): morphological and clinical evaluation — F. Bolat, T. Canpolat, et al. (2012)
• Benign peritoneal cystic mesothelioma mimicking peritoneal tuberculosis — C. Soltani, K.B. Abdallah, et al. (2022)
• Peritoneal well-differentiated papillary mesothelioma coexisting with endometrial adenocarcinoma mimicking peritoneal carcinomatosis: A case report — Y.Y. Chen, P.C. Li, et al. (2020)
• Pleural tuberculosis mimicking malignant mesothelioma — W. Dawood, D. La Garza Henriette, et al. (2020)
• Free-floating intra-peritoneal mesothelial cyst with histologic properties of amniotic epithelium in term pregnancy: Report of two cases — K.P. Tsui, H.J. Tsai, et al. (2016)

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