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<p>Dedifferentiated liposarcoma (DDLPS) can exhibit myxoid morphology that closely mimics myxoid liposarcoma (MLPS), creating significant diagnostic challenges. <i>DDIT3</i> immunohistochemistry (IHC), a specific marker for MLPS, has been reported in a subset of DDLPS cases, but its frequency, staining pattern, and clinical significance remain poorly characterised. We retrospectively analysed 46 DDLPS cases with prominent myxoid features (≥ 10% myxoid component) confirmed by <i>MDM2</i> IHC and fluorescence in situ hybridisation (FISH), treated at a single tertiary centre between January 2007 and January 2026. <i>DDIT3</i> IHC was scored using a semiquantitative H-score system. <i>DDIT3</i> positivity occurred in 11 of 46 cases (23.9%, 95% CI: 12.6–38.8%), predominantly as focal staining (9/11, 81.8%). All <i>DDIT3</i>-positive cases exhibited myxoid components comprising &gt; 25% of tumour volume, versus variable myxoid extent in <i>DDIT3</i>-negative cases (<i>p</i> &lt; 0.001). Mean H-score in <i>DDIT3</i>-positive cases was 48.6 ± 32.4 (range 15–120), significantly lower than in true MLPS controls (mean 278 ± 22, <i>p</i> &lt; 0.001). Tumour size &gt; 15&#xa0;cm significantly increased the risk of local recurrence (risk ratio [RR] = 2.31, 95% CI: 1.02–5.24, <i>p</i> = 0.048). <i>DDIT3</i> expression showed no significant association with local recurrence (<i>p</i> = 0.337), distant metastasis (<i>p</i> = 0.825), or mortality (<i>p</i> = 0.805). Kaplan–Meier analysis revealed no significant difference in overall survival (log-rank <i>p</i> = 0.782) or recurrence-free survival (log-rank <i>p</i> = 0.614) between <i>DDIT3</i>-positive and <i>DDIT3</i>-negative groups. <i>DDIT3</i> positivity in DDLPS with myxoid features predominantly produces focal, low-intensity staining that distinguishes it from true MLPS. <i>DDIT3</i> expression reflects chromosomal co-amplification within the <i>12q13-15</i> amplicon and lacks prognostic significance. Combined <i>MDM2</i> and <i>DDIT3</i> IHC with careful morphological assessment aids differential diagnosis, particularly when molecular testing is unavailable.</p>

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MDM2 and DDIT3 coexpression in dedifferentiated liposarcoma with myxoid features: a retrospective cohort study

  • 期刊论文

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  • 发表日期：

    2026年5月18日

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  • Kivilcim Eren Ates,
  • Gulfiliz Gonlusen,
  • Seyda Erdogan,
  • Akif Mirioglu

摘要

Dedifferentiated liposarcoma (DDLPS) can exhibit myxoid morphology that closely mimics myxoid liposarcoma (MLPS), creating significant diagnostic challenges. DDIT3 immunohistochemistry (IHC), a specific marker for MLPS, has been reported in a subset of DDLPS cases, but its frequency, staining pattern, and clinical significance remain poorly characterised. We retrospectively analysed 46 DDLPS cases with prominent myxoid features (≥ 10% myxoid component) confirmed by MDM2 IHC and fluorescence in situ hybridisation (FISH), treated at a single tertiary centre between January 2007 and January 2026. DDIT3 IHC was scored using a semiquantitative H-score system. DDIT3 positivity occurred in 11 of 46 cases (23.9%, 95% CI: 12.6–38.8%), predominantly as focal staining (9/11, 81.8%). All DDIT3-positive cases exhibited myxoid components comprising > 25% of tumour volume, versus variable myxoid extent in DDIT3-negative cases (p < 0.001). Mean H-score in DDIT3-positive cases was 48.6 ± 32.4 (range 15–120), significantly lower than in true MLPS controls (mean 278 ± 22, p < 0.001). Tumour size > 15 cm significantly increased the risk of local recurrence (risk ratio [RR] = 2.31, 95% CI: 1.02–5.24, p = 0.048). DDIT3 expression showed no significant association with local recurrence (p = 0.337), distant metastasis (p = 0.825), or mortality (p = 0.805). Kaplan–Meier analysis revealed no significant difference in overall survival (log-rank p = 0.782) or recurrence-free survival (log-rank p = 0.614) between DDIT3-positive and DDIT3-negative groups. DDIT3 positivity in DDLPS with myxoid features predominantly produces focal, low-intensity staining that distinguishes it from true MLPS. DDIT3 expression reflects chromosomal co-amplification within the 12q13-15 amplicon and lacks prognostic significance. Combined MDM2 and DDIT3 IHC with careful morphological assessment aids differential diagnosis, particularly when molecular testing is unavailable.