Spontaneous regression of colorectal liver metastasis with coexisting IgG4-rich inflammatory pseudotumor-like changes: a case report.
Shoichiro Mizukami, Tatsuya Shonaka, Tomoki Takizawa et al.
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Case in brief
A 71-year-old man developed hepatic lesions in segments S5 and S7, diagnosed on imaging as colorectal liver metastases, eight months after surgery for rectal cancer. Partial hepatectomy showed necrotic adenocarcinoma in the S7 lesion alongside IgG4-rich inflammatory pseudotumor-like changes. Subsequent evaluation found markedly elevated serum IgG4 and IgG4-positive plasma cells in mediastinal lymph nodes, meeting diagnostic criteria for systemic IgG4-related disease. He remained recurrence-free 20 months after surgery without adjuvant chemotherapy or steroid therapy.
What made this case unusual
The resected lesion contained both necrotic metastatic adenocarcinoma, interpreted as possible spontaneous regression, and IgG4-rich inflammatory pseudotumor-like changes.
Diagnostic / clinical pearl
A hepatic lesion diagnosed radiologically as colorectal metastasis may show necrotic tumor with coexisting IgG4-rich inflammatory changes; systemic evaluation can identify IgG4-related disease.
Why it matters
The case illustrates a possible clinicopathological overlap between spontaneous tumor regression and IgG4-related hepatic inflammation, while the mechanism remains unclear.