Hyperplastic mesothelial cells in pelvic and abdominal lymph node sinuses mimicking metastatic ovarian microinvasive serous borderline tumor.

Hyperplastic mesothelial cells within pelvic and abdominal lymph nodes were encountered in the staging procedure of a 32-year-old woman with a left ovarian microinvasive serous borderline tumor. Mesothelial hyperplasia was noted in the pelvic and abdominal peritoneum. Intranodal mesothelial cells occupied the subcapsular sinus with subadjacent interfollicular sinuses involved less strikingly. These mesothelial cells were originally misdiagnosed as a metastatic serous borderline tumor. Histologic review and immunohistochemistry confirmed mesothelial origin. This case represents the second reported example of mesothelial cells within the lymph nodes of patients with ovarian serous tumors. Similar involvement of the mediastinal, cervical and internal mammary lymph nodes has been described in several patients with pleural effusions without neoplastic cells. Intranodal mesothelial cells should be distinguished from metastasis--an error ending in upper staging of a case.