Perivascular epithelioid cell tumor (PEComa) of the pancreas: Immunoelectron microscopy and review of the literature

Pathology International (Impact Factor: 1.69). 08/2009; 59(9):650 - 655. DOI: 10.1111/j.1440-1827.2009.02421.x


A perivascular epithelioid tumor (PEComa) is a rare tumor probably arising from the perivascular epithelioid cells. Only three cases of pancreatic PEComa have been reported in the English-language literature. The present report describes an extremely rare case of pancreatic PEComa. A 47-year-old Japanese woman complained of lower abdominal pain and a well-demarcated solid tumor was found in the pancreatic head. There was no history of tuberous sclerosis complexes. Pylorus-preserving pancreaticoduodenectomy was thus performed. There was a well-demarcated, solid tumor measuring 17 mm in the pancreatic head. The tumor was composed of a diffuse proliferation of epithelioid tumor cells with many blood vessels but no adipose tissue. The tumor cells expressed HMB45 and α-smooth muscle actin. Ultrastructurally, the tumor cells possessed many membrane-bound granules that were positive for HMB45 on immunoelectron microscopy. The results of immunoelectron microscopy show that some PEComas possess not only typical melanosomes or premelanosomes but also aberrant melanosomes.

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    ABSTRACT: A 37-year-old Japanese man with a solid and cystic pancreatic mass was referred to our hospital. Computed tomography revealed a well-demarcated solid and cystic mass measuring approximately 3.0 cm in diameter in the pancreatic body. The patient underwent middle segment pancreatectomy, and the retrieved tumor specimen was found to be a well-demarcated solid and cystic lesion measuring 3.0 x 3.0 cm. On histological examination, the cyst walls were found to be lined with a monolayer of non-atypical tall columnar epithelial cells. The solid areas surrounded the cystic ones and showed storiform proliferation of spindle cells that contained round, oval, or elongated nuclei and were present among abundant collagen fibers. The solid areas sent phylloid projections into the cystic spaces and the main pancreatic duct. The spindle cells were found to be diffusely positive for alpha-smooth muscle actin, desmin, and h-caldesmon on immunohistochemical analysis. Electron microscopy revealed that these cells possessed well-developed myofilaments with dense bodies, pinocytic vesicles, and basal lumina. Neither metastasis nor local invasion was detected. After the operation (4 years), tumor recurrence has not occurred. The main differential diagnoses of spindle cell tumors are leiomyomas, leiomyosarcomas, inflammatory myofibroblastic tumors, solitary fibrous tumors, extra-gastrointestinal stromal tumors, and schwannomas. However, the histological findings in the present case differed from those of these tumors. The present lesion is the first reported case of a primary pancreatic phyllodes tumor.
    Archiv für Pathologische Anatomie und Physiologie und für Klinische Medicin 02/2010; 456(5):587-93. DOI:10.1007/s00428-010-0893-9 · 2.65 Impact Factor
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    ABSTRACT: Perivascular epithelial cell tumors (PEComas) are a family of rare mesenchymal neoplasms which share cellular, immunohistochemical and ultrastructural characteristics but are found in different visceral and soft tissue sites. PEComas of the pancreas are extremely rare neoplasms. We describe a 49-year-old male who was incidentally diagnosed with a pancreatic mass. Endoscopic ultrasound-guided biopsy suggested a PEComa. An uneventful pylorus-preserving pancreaticoduodenectomy was thus performed. The tumor was a solid well-circumscribed mass in the pancreatic head with dilatation of the main pancreatic duct. Histopathology revealed a well-circumscribed and vascularized neoplasm, measuring 32x27x30 mm, composed of epithelioid smooth muscle cells with clear cytoplasm rich in glycogen. The tumor exhibited immunoreactivity to alpha-smooth muscle actin and to melanoma-associated antigen HMB-45. Although rare, pancreatic PEComas should be included in the differential diagnosis of a pancreatic mass. Currently, the paucity of cases published makes it impossible to predict the behavior and prognosis of these tumors or to advocate an optimal therapy.
    JOP: Journal of the pancreas 01/2011; 12(1):55-8.

  • Zhonghua bing li xue za zhi Chinese journal of pathology 01/2011; 40(1):59-64. DOI:10.3760/cma.j.jssn.0529-5/07.2011.01.018
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