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In recent years, the incidence of membranous nephropathy (MN) with malignancy has gradually increased, but the clinical and pathological characteristics of these patients are still unclear.
Patients diagnosed with renal biopsy-proven MN and comorbid malignancy detected within 5 years before and after MN diagnosis were included. The control group were diagnosed with renal biopsy-proven IMN with no malignancy and no other clear secondary cause for MN. We present a comprehensive analysis of MN with concomitant malignancy in our cohort and literature review.
A total of 19 MN patients with concomitant malignancy were evaluated at our center; among them, 13 (68.4%) were male, and the median age was 57.0 (45.0, 69.0) years. Malignancy occurred after the onset of renal disease in 61.1% of patients, with digestive system malignancy (36.8%) ranking as the predominant type. 8 (8/11) patients achieved either PR or CR during the follow-up period. Most patients had pathology typical of IMN. IF showed strong positivity for IgG (100%), whereas only 13 (68.4%) patients were positive for C3. IEM showed electron-dense deposits predominantly locatted in subepithelial. Specific MN antigen staining of renal tissues from 19 patients showed that the highest percentage was 68.4% (13/19) for PLA2R-only positivity followed by 15.8% (3/19) for THSD7A-only positivity. Specific MN antigen staining of malignant tissue was performed in 5 patients whose tumor samples were available. Only 2 patients expressed the same antigen on kidney and tumor. Screening 17 articles encompassing a total of 21 patients in whom MN-specific antigen staining was performed on both renal and tumor tissues simultaneously. Among these patients, 71.4% (15/21) were male, with a median age of 61.0 years (56.3, 72.8). In this cohort, malignancy was diagnosed before or simultaneously with MN in 15 patients (75.0%), with digestive system malignancy constituting the most prevalent comorbid malignancy, at 33.3%. Notably, THSD7A accounted for the highest proportion of MN antigens, at 66.7% (14/21); among these patients, 78.6% (11/14) also exhibited positive tumor THSD7A staining. Of the 21 patients, 72.2% (13/18) achieved CR or PR. No significant difference between the baseline characteristics was observed between the 19 patients from our center and 21 patients documented in the literature. Therefore, the clinicopathological data of these 40 patients were pooled and compared with 101 IMN patients without malignancy at our center. Compared to patients without malignancy, MN patients with malignancy were older at the time of renal biopsy (P = 0.017), had a lower eGFR (P = 0.035) and demonstrated a lower rate of CR or PR after treatment (P < 0.001). The rate of PLA2R positivity in the glomeruli of MN patients with concomitant malignancy was significantly lower (40.0% vs. 92.1%, P < 0.001), while the rate of THSD7A positivity was significantly higher (42.5% vs. 2.0%, P < 0.001). Renal tissue IgG subclass staining showed that the rate of IgG4 positivity was significantly decreased compared with that in IMN patients (59.3% vs. 90.1%, P < 0.001), and the rate of IgG2 positivity was significantly increased (36.0% vs. 16.5%, P = 0.033).
To conclude, malignancy screening should be more actively performed for MN patients presenting with the above characteristics.