Primary Malignant Mesothelioma Presenting as an Umbilical Tumor

Malignant mesothelioma presenting as a primary umbilical tumor is not reported in the English literature, to our knowledge. We present a 63-year-old woman with a painless and initially skin colored nodule in the umbilical area, which within one month became erythematous. The performed biopsy revealed an infiltrating glandular and ductal proliferation involving the dermis, subcutaneous fat and underlying skeletal muscle embedded in a loose and mucinous stroma. The tumor cells were of medium size with round to oval nuclei and prominent nucleoli. Mitoses were conspicuous. The tumor cells showed a positive reaction for kermix, EMA, CK5/6, calretinin and CK7 and a negative reaction for CK20, CEA, Ber-Ep4, S100 protein, TTF-1, PRP, ERP, and Leu-7. Since calretinin is both a sensitive and specific marker of reactive and neoplastic mesothelial cells, a diagnosis of malignant mesothelioma, epithelioid variant, was made. The performed exploratory laparotomy showed no evidence of malignancy and wide excision of the umbilical area showed no evidence of residual tumor. Follow-up examinations of the patient with repeated CT scans for the past two years were negative for recurrent or metastatic disease. We conclude that this malignancy likely developed in a setting of umbilical abnormalities associated with mesothelial remnants.