A case of Sister Mary Joseph's nodule from prostatic cancer.

The metastasis of a visceral malignancy to the umbilicus is known as "Sister Mary Joseph's nodule" (SMJN). We recently encountered an 80-year-old man in whom umbilical metastasis of prostatic cancer was revealed during the course of treatment. The lesion was a red, firm, elastic nodule, 2.5 cm in diameter, with a bumpy, irregular surface, but without subjective symptoms. In histopathological examination, atypical cells with intensely stained, small quasi-circular nuclei and weakly eosinophilic cytoplasm were found in all layers of the dermis. In some parts of these tumor cells, a gland-like structure was observed. Immunohistochemical investigation of the invading tumor cells disclosed immunoreactivity for prostate specific antigen and prostatic acid phosphatase, supporting a diagnosis of SMJN from prostatic cancer. His general condition gradually deteriorated, and he died 2 months later. Prostate cancer often metastasizes to bones and lymph nodes, but rarely to the skin. Of all the cases of cutaneous metastasis of prostate cancer reported in Japan, only three metastases have occurred to the umbilical region. The present case is therefore an example of a very rare condition.