IMP dehydrogenase rod/ring structures in acral melanomas

Area of Science:

• Oncology
• Biochemistry
• Pathology

Background:

• Acral lentiginous melanoma (ALM) is an aggressive melanoma subtype.
• The enzyme IMPDH (Inosine Monophosphate Dehydrogenase) forms filamentary structures (rods/rings, RR) linked to high GTP demand in proliferative cells.

Purpose of the Study:

• To investigate the presence and diagnostic utility of IMPDH-based RR structures in ALM.
• To determine if RR structures correlate with ALM aggressiveness.

Main Methods:

• Immunohistochemical analysis of IMPDH2 in 45 ALM and 59 nevi tissue samples.
• Quantification of RR-positive cells and ROC curve analysis for diagnostic accuracy.
• Correlation of RR status with histopathological features like Breslow thickness.

Main Results:

• IMPDH-based RR structures were observed more frequently in ALM than in nevi (80% vs. 15%, p < .001).
• ROC analysis yielded an AUC of 0.88, with a cutoff of 5.5% RR-positive cells showing 80% sensitivity and 85% specificity for ALM.
• RR-positive ALM specimens were more likely to have a Breslow thickness > 4.0mm (71% vs. 29%, p = .039).

Conclusions:

• IMPDH-based RR structures are significantly more prevalent in ALM compared to nevi.
• Screening for RR structures in biopsies may serve as a valuable diagnostic aid for ALM.
• The presence of RR structures may indicate a more malignant tumor phenotype in ALM.