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Fine needle aspiration cytology of well-differentiated papillary mesothelioma: a case report
Yun Gong1, Rulong Ren, Nelson G Ordóñez
1Department of Pathology, The University of Texas M D Anderson Cancer Center, Houston 77030, USA. yungong@mdanderson.org
Background:
Well-differentiated papillary mesothelioma (WDPM) is an uncommon subtype of mesothelioma that typically occurs in the peritoneum of women without a history of asbestos exposure and usually follows an indolent clinical course. Fine needle aspiration (FNA) of this type of tumor has rarely been reported.
Case:
A 64-year-old woman with 11-year history of colon cancer and an adrenal nodule was found, on abdominal computed tomography, to have a mass in the right lobe of the liver. Aspirates of the mass were composed of abundant, tight, papillary groups, monolayered, pavementlike sheets; and scattered single cells with minimal atypia. The cell block showed a predominantly papillary growth pattern and a single layer of bland, cuboidal to flattened covering cells with stout, fibrovascular cores containing clusters of foamy histiocytes. Tumor cells in the focal tubulopapillary and solid areas were mingled with inflammatory cells and showed slightly more atypia than did the cells covering the papillae. The differential diagnoses were intrahepatic papillary neoplasm, including well-differentiated mesothelioma and metastatic low grade papillary serous carcinoma. At surgery the tumor was found to be a pedunculated peritoneal mass that arose from the posterior surface of the right lobe of the liver. The mesothelial origin of the tumor was confirmed by both immunoperoxidase study and electron microscopic examination, which demonstrated long, slender, branching microvilli.
Conclusion:
Familiarity with the cytomorphologic features and clinical presentation of WDPM, knowledge of the exact anatomic location and consideration of the appropriate differential diagnosis combined with ancillary studies are the keys to an accurate diagnosis.
Insights
This case report details a rare instance of well-differentiated papillary mesothelioma (WDPM) found in the liver. Diagnosis requires understanding cytomorphology, clinical presentation, and differential diagnoses for this uncommon mesothelioma subtype.
Area of Science:
- Oncology
- Pathology
- Cytopathology
Background:
- Well-differentiated papillary mesothelioma (WDPM) is a rare mesothelioma subtype, typically originating in the peritoneum of women without asbestos exposure.
- WDPM usually presents an indolent clinical course, and fine needle aspiration (FNA) findings are infrequently reported.
Observation:
- A 64-year-old woman with a history of colon cancer and an adrenal nodule was diagnosed with a liver mass via CT scan.
- Aspirates revealed papillary groups, sheets of cells, and scattered single cells with minimal atypia. Cell block analysis showed a papillary growth pattern with bland covering cells and foamy histiocytes.
- Surgical findings confirmed a pedunculated peritoneal mass arising from the liver's posterior surface. Immunoperoxidase and electron microscopy confirmed mesothelial origin with characteristic microvilli.
Findings:
- The study describes the cytomorphologic features of WDPM in a liver mass, including papillary structures and bland-appearing cells.
- Differential diagnoses included intrahepatic papillary neoplasm, WDPM, and metastatic low-grade papillary serous carcinoma.
- Immunohistochemistry and electron microscopy confirmed the mesothelial origin of the tumor.
Implications:
- Accurate diagnosis of WDPM relies on recognizing its cytomorphologic features and clinical context.
- Considering the differential diagnosis and utilizing ancillary studies are crucial for correct WDPM identification.
- This case highlights the importance of comprehensive evaluation for diagnosing rare peritoneal tumors presenting as liver masses.
