A Descriptive Summary of Tumor-Associated MUC1 (TA-MUC1) Expression in Epithelial Malignancies: A Systematic Review of Case Reports and Case Series

Our plain-English summary of A Descriptive Summary of Tumor-Associated MUC1 (TA-MUC1) Expression in Epithelial Malignancies: A Systematic Review of Case Reports and Case Series, by R. Ohta, K. Nishikawa, K. Tanaka, et al (Curēus, 2025).

The study

• Authors: R. Ohta, K. Nishikawa, K. Tanaka, C. Sano, H. Hayashi
• Journal: Curēus
• Published: 2025;17(10):e95636
• Type of article: Review
• Read it: PubMed · Publisher · Free full text

Abstract

Tumor-associated MUC1 (TA-MUC1) is a hypoglycosylated variant of MUC1 that is aberrantly expressed in many epithelial malignancies. Its limited presence in normal tissues and immunogenic properties suggest potential as a target for antibody-drug conjugates and cancer immunotherapy. However, the clinicopathological spectrum and therapeutic context of TA-MUC1-positive tumors remain insufficiently characterized. We conducted a systematic review of case reports and case series describing immunohistochemically confirmed TA-MUC1 expression in malignant tumors. A total of 73 individual cases from 61 publications were included. Data extraction covered demographics, tumor features, TA-MUC1 expression, treatments, outcomes, and associated biomarkers. TA-MUC1 expression was identified across a wide range of tumor types, most frequently in gastrointestinal, breast, and gynecologic cancers, but also in less common malignancies such as sarcomatoid carcinoma and pleural mesothelioma. Expression was frequently retained in metastatic sites. Immunohistochemical staining varied in intensity and methodology, with strong expression often associated with recurrence or aggressive clinical behavior. Multimodal therapy was commonly reported. Across cases, progression-free survival (PFS) was available in 56 of 73 (76.7%) cases. Among these, 47 of 56 (83.9%) had a documented progression event, whereas nine of 56 (16.1%) were censored (progression-free at last follow-up). The median PFS was 12.0 months (IQR 6.0-19.5; range 0.0-118.0 months). Overall survival (OS) was available in 56 of 73 (76.7%) cases. Among these, 14 of 56 (25.0%) deaths were reported, and 42 of 56 (75.0%) observations were censored (alive at last follow-up). The median OS was 12.0 months (IQR 8.0-26.0; range 0.5-118.0 months). Co-expression with biomarkers such as programmed death-ligand 1 (PD-L1) and human epidermal growth factor receptor 2 (HER2) was occasionally observed. These findings demonstrate that TA-MUC1 has been documented in diverse malignancies, including rare and metastatic presentations. The descriptive evidence supports its potential relevance as a therapeutic target and highlights the need for standardized evaluation and prospective studies.

Copyright © 2025, Ohta et al.

In plain English

This article was a systematic review of published case reports and case series, not a new study of patients. The authors searched PubMed, Embase and Web of Science for reports of cancers in which tumor-associated MUC1 (TA-MUC1), an altered form of a cell-surface protein, was found by tissue staining. They included 73 patients from 61 publications dated 1999 to 2025, most of them from Japan. The patients were 41 males and 32 females, with a median age of 65 years. Pancreatic cancer was the most frequently reported type (14 cases). The authors reported three cases of pleural mesothelioma of the epithelioid subtype. The article did not discuss asbestos. Among the 56 cases with progression-free survival data, the median was 12.0 months. Among the 56 cases with overall survival data, 14 deaths were reported and the median was 12.0 months. The authors concluded that TA-MUC1 has been reported across many cancers. They called their findings hypothesis-generating, citing publication bias, inconsistent staining methods, a small sample drawn mostly from Japan, and the absence of TA-MUC1-negative comparison cases.

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: Systematic review of published case reports and case series, with descriptive (narrative) synthesis only; no meta-analysis
• Who was studied: 73 individual patients with TA-MUC1-positive malignant tumors, drawn from 61 publications (1999 to 2025) found in PubMed, Embase and Web of Science; 41 males and 32 females, median age 65 years (range 33 to 92); most reports from Japan
• Exposure: No asbestos or other environmental or occupational exposure was studied. The review concerned TA-MUC1 expression in tumors, detected by immunohistochemistry.
• Main results:
  • Sixty-one case reports or case series met the inclusion criteria.
  • Of the 73 patients, 41 were male and 32 female, with a median age of 65 years (range 33 to 92).
  • Pancreatic cancer was the most frequently reported cancer type among the 73 cases (n = 14, 19.2%).
  • TA-MUC1 expression was reported in three cases of pleural mesothelioma, all of the epithelioid subtype.
  • After the authors grouped the reported staining into categories, strong TA-MUC1 expression was found in 20 of the 73 cases (27.4%), moderate in 8 (11.0%) and weak in 6 (8.2%). The remaining 39 cases (53.4%) were reported only as positive.
  • Only 2 of the 73 cases (2.7%) reported paired primary-versus-metastasis comparisons, and both showed no observable difference in TA-MUC1 expression.
  • Progression-free survival was available for 56 of 73 cases. Of these, 47 of 56 had a documented progression event. The median PFS was 12.0 months (IQR 6.0 to 19.5; range 0.0 to 118.0 months).
  • Overall survival was available for 56 of 73 cases. Of these, 14 of 56 (25.0%) deaths were reported and 42 of 56 (75.0%) patients were alive at last follow-up. The median OS was 12.0 months (IQR 8.0 to 26.0; range 0.5 to 118.0 months).
  • PD-L1 status was reported in 9 cases, of which 5 were positive.
  • HER2 overexpression was documented in 4 cases.
• The authors' conclusion: The authors concluded that TA-MUC1 expression has been reported across a broad range of epithelial cancers, including rare and metastatic sites, and that it could be a potential treatment target. They added that the evidence is limited, that the results should be interpreted with caution and treated as hypothesis-generating, and that large prospective studies are needed.
• Limitations the authors state:
  • Relying only on case reports and case series introduces selection and publication bias.
  • Immunohistochemical methods varied (antibody clones, staining protocols, scoring), so expression intensity could not be meaningfully compared across cases.
  • The sample was small and mostly from Japan, which limits generalizability.
  • Survival outcomes were inconsistently reported and prone to bias, and the authors described them as illustrative only.
  • There were no TA-MUC1-negative comparison cases, so prognostic or predictive value could not be evaluated.

Topics

Medical terms in this study, explained in our Lexicon: Systematic Review, Immunotherapy, Biomarker, Sarcomatoid, Carcinoma, Pleural Mesothelioma, Immunohistochemistry, Multimodal Therapy.

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