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Abstract
Rationale:
Perivascular epithelial cell tumors (PEComas) of the pancreas are rare mesenchymal
tumors and, to our knowledge, only 20 cases have been reported to date.
Patient concerns:
We report a 43-year-old female who presented with upper abdominal pain for 1 year.
She underwent an exploratory laparotomy at a local hospital, which failed to resect
the tumor. Five months later, she came to the Chinese National Cancer Center for surgery.
Preoperative imaging revealed an 11.5-cm-sized mass located in the head of the pancreas.
At the microscopic level, the tumor was composed of epithelioid and spindle cells
possessing clear to focally granular eosinophilic cytoplasm, which grew in a nested
and alveolar pattern around blood vessels. The tumor cells showed immunoreactivity
for human melanoma black 45 (HMB-45), but did not express epithelial or endocrine
markers.
Diagnoses:
Pancreatic PEComa.
Interventions:
Pancreaticoduodenectomy, partial hepatectomy, and vascular replacement were performed.
After the surgery, the patient received 4 cycles of chemotherapy.
Outcomes:
The patient is free of recurrence and metastasis 1.5 years after surgical resection.
Lessons:
PEComa should be recognized as a preoperative differential diagnosis of pancreatic
tumors. For treatment, removal of the tumor should be attempted, and in the case of
tumors with malignant tendencies, the addition of chemotherapy should be considered.
PEComas, occasionally associated with the tuberous sclerosis complex, are defined by the presence of perivascular epithelioid cells that coexpress muscle and melanocytic markers. This family of tumors includes angiomyolipoma (AML), clear cell sugar tumor of the lung (CCST), lymphangioleiomyomatosis (LAM), and very rare tumors in other locations. Because non-AML/non-LAM PEComas are extremely rare and their natural history and prognostic features undefined, we present our experience with 26 PEComas of soft tissue and the gynecologic tract, the largest series to date. We also performed a detailed review of the literature, with special attention to features predictive of clinical behavior. All PEComas exclusive of AML and LAM were retrieved from our consultation files. Immunohistochemistry for pan-cytokeratin (CK), S-100 protein, smooth muscle actins (SMA), desmin, vimentin, HMB45, Melan-A, microphthalmia transcription factor (MiTF), TFE3, CD117, and CD34 was performed. Clinical follow-up information was obtained. Fisher's exact test was performed. The median patient age was 46 years (range, 15-97 years); there was a marked female predominance (22 females, 4 males). Sites of involvement included the omentum or mesentery (6 cases), uterus (4 cases), pelvic soft tissues (3 cases), abdominal wall (2 cases), uterine cervix (2 cases), and vagina, retroperitoneum, thigh, falciform ligament, scalp, broad ligament, forearm, shoulder, and neck (1 case each). The tumors ranged from 1.6 to 29 cm in size (median, 7.8 cm). Tumors were epithelioid (N = 9), spindled (N = 7), or mixed (N = 10). Multinucleated giant cells were present in 18 cases. High nuclear grade was noted in 10 cases, high cellularity in 7 cases, necrosis in 8 cases, and vascular invasion in 3 cases. Mitotic activity was 0 to 50 mitotic figures (MF)/50 high power fields (HPF) (median, 0 MF/50 HPF) with atypical MF in 6 cases. IHC results were: SMA (20/25), desmin (8/22), HMB45 (22/24), Melan-A (13/18), MITF (9/18), S-100 protein (8/24), CK (3/23), vimentin (12/14), TFE3 (5/17), c-kit (1/20), and CD34 (0/7). Clinical follow-up (24 of 26 patients, 92%; median, 30 months; range, 10-84 months) showed 3 local recurrences and 5 distant metastases. At last available clinical follow-up, 2 patients (8%) were dead of disease, 4 patients (17%) were alive with metastatic or unresectable local disease, and 18 patients (75%) were alive with no evidence of disease. No patient in our series had a history of tuberous sclerosis complex. Recurrence and/or metastasis was strongly associated tumor size > median size (8 cm), mitotic activity greater than 1/50 HPF, and necrosis. We conclude that PEComas of soft tissue and gynecologic origin may be classified as "benign," "of uncertain malignant potential," or "malignant." Small PEComas without any worrisome histologic features are most likely benign. PEComas with nuclear pleomorphism alone ("symplastic") and large PEComas without other worrisome features have uncertain malignant potential. PEComas with two or more worrisome histologic features should be considered malignant. Occasional PEComas express unusual markers, such as S-100 protein, desmin, and rarely CK. The role of TFE3 in PEComas should be further studied.
The perivascular epithelioid cell (PEC) is a cell type constantly present in a group of tumors called PEComas. PEC expresses myogenic and melanocytic markers, such as HMB45 and actin. Recently, recurrent chromosomal alterations have been demonstrated in PEC. At present, PEComa is a widely accepted entity. In the past 10 years, the use of this term has allowed to report and describe numerous cases permitting to start highlighting the biology of this group of lesions. PEComas are related to the genetic alterations of tuberous sclerosis complex (TSC), an autosomal dominant genetic disease due to losses of TSC1 (9q34) or TSC2 (16p13.3) genes which seem to have a role in the regulation of the Rheb/mTOR/p70S6K pathway. There are some open questions about PEComas regarding its histogenesis, the definition of epithelioid angiomyolipoma and the identification of the histological criteria of malignancy. An innovative therapeutic trial using rapamycin is under way for tumors occurring in TSC such as renal angiomyolipoma and lymphangioleiomyomatosis. Its success could provide the rationale for the use of the same drug in other lesions composed of PECs, especially in the malignant ones.
This review article summarizes our current understanding of the clinical, pathologic, immunohistochemical, and genetic aspects of perivascular epithelioid cell neoplasms, a rare group of related tumors defined by both morphologic and immunophenotypic criteria.
[a
]Department of Pancreatic and Gastric Surgery, National Cancer Center/Cancer Hospital,
Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing
[b
]Department of Oncology, Bozhou People's Hospital, Bozhou
[c
]Department of Abdominal Surgery, Cancer Hospital of Chinese Academy of Medical Sciences,
Shenzhen Center, Shenzhen Cancer Hospital, Shenzhen
[d
]State Key Laboratory of Molecular Oncology, National Cancer Center/Cancer Hospital,
Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing
[e
]Department of Medical Oncology, Affiliated Hospital of Qinghai University, Xining,
China.
Author notes
[∗
]Correspondence: Chengfeng Wang, Department of Pancreatic and Gastric Surgery, National
Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union
Medical College, Chaoyang District, Beijing, China (e-mail:
lifeofwater@
123456126.com
).
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as long as it is passed along unchanged and in whole, with credit to the author.
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