Focal Eosinophilic Necrosis of the Liver in Patients with Underlying Gastric or Colorectal Cancer: CT Differentiation from Metastasis

OBJECTIVE: To determine the helical CT findings which help differentiate between focal eosinophilic necrosis (FEN) of the liver and metastasis in patients with underlying gastric or colorectal cancer. MATERIALS AND METHODS: In 21 patients with underlying gastric and colorectal cancer examined during a recent 18-month period, the presence of FEN (n=90) was proven at CT. The diagnosis was verified by biopsy in eight patients and by the transient nature of the findings related to peripheral eosinophilia (>10%) in the remainder. For comparison, 20 consecutive patients with pathologically proven hepatic metastasis from gastric or colorectal cancer (n=158) were selected. Single-phase helical CT images (7-mm collimation, pitch 1:1) were independently analyzed in a random order by two blinded readers. The parameters evaluated included the margin (depicted border, fuzzy), shape (spherical, non-spherical), attenuation (subtle hypoattenuation, hypoattenuation), and the presence or absence of rim enhancement. RESULTS: FEN far more frequently showed a fuzzy margin (81%, 84%), subtle hypoattenuation (89%, 91%), and a non-spherical shape (84% for both readers) than metastasis, for which the respective findings were 6%, 22%; 20%, 39%; and 15%, 23%. Rim enhancement was seldom found in FEN (0%, 2%), but was recognized by both readers in 40% of metastases. For all parameters, the results were statistically significant (p < .01), and showed that both readers correctly differentiated FEN from metastasis in 78% of the patients (32/41). Interobserver agreement was, in addition, excellent (κ= 0.66). CONCLUSION: When focal hepatic lesions with a fuzzy margin, non-spherical shape and subtle hypoattenuation without rim enhancement are found, the possibility of FEN should be considered even in patients with underlying gastrointestinal malignancy.