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Published on: October 20, 2019
Efficacy and Cost-Effectiveness of MDM2 Fluorescence In Situ Hybridization (FISH) in Morphologically Atypical
Zobash Noor1, Shaymaa Hegazy2, Rana Naous1
1Pathology, University of Pittsburgh Medical Center, Pittsburgh, USA.
Background:
Spermatic cord lipomas originate from preperitoneal adipose tissue within the internal spermatic fascia and are found in 20%-70% of all inguinal hernia repairs. Morphologically, spermatic cord lipomas may harbor some atypical features, including increased stromal cellularity with thickened fibrous bands, occasional lipoblasts, and stromal nuclear atypia or hyperchromasia, raising concern for well-differentiated liposarcoma (WDLS) versus reactive-type atypia. Fluorescence in situ hybridization (FISH) for MDM2 amplification would be the gold standard test in such cases. The aim of this study was to evaluate the efficacy and cost-effectiveness of MDM2 FISH in diagnostically discrimination morphologically atypical spermatic cord lipoma cases at our institution.
Methods:
All cases with "specimen type" labeled as "spermatic cord lipoma" between 2018 and 2023 were retrospectively retrieved from our institutional archives. Cases were included in the study group if they had MDM2 FISH performed. Cases with a prior history of spermatic cord well-differentiated liposarcoma with positive MDM2 amplification were excluded. MDM2 amplification status and corresponding final diagnosis were recorded.
Results:
Three hundred twenty specimens labelled as spermatic cord lipoma were retrieved from our archives. Forty-three out of 320 had MDM2 FISH performed. All 43 cases demonstrated atypical features and appeared morphologically similar. Only one out of 43 (2.3%) cases demonstrated a positive MDM2 amplification result, thus labeling it as an incidental WDLS (11 cm) in the setting of an inguinal hernia repair for which the patient required a subsequent orchiectomy. The remaining 42 cases (97.7%) harbored reactive-type atypia with negative FISH results and were diagnosed as spermatic cord lipomas.
Conclusion:
Our results indicate that 2.3% of morphologically atypical specimens labeled as spermatic cord lipoma at our institution are in fact well-differentiated liposarcomas. These findings prove the efficacy of MDM2 FISH in diagnosing WDLS in the setting of atypical spermatic cord lipoma labeled specimens. Although 97.7% of our spermatic cord lipomas harbored reactive-type atypia with negative FISH results, which argues against the cost-effectiveness of such testing, we propose performing FISH analysis in cases greater than 10 cm in size to avoid misdiagnosis and ensure optimal patient care.
