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Am J Surg Pathol. 2018 Oct;42(10):1370-1383. doi: 10.1097/PAS.0000000000001119.

Uterine PEComas: A Morphologic, Immunohistochemical, and Molecular Analysis of 32 Tumors.

Author information

1
Department of Pathology and Laboratory Medicine, Lahey Hospital and Medical Center, Burlington.
2
Department of Pathology, Hospital Prof. Doutor Fernando Fonseca, EPE, Amadora, Portugal.
3
Department of Pathology and Laboratory Medicine, University of Miami Miller School of Medicine, Miami, FL.
4
Department of Pathology, Cancer Research Institute Ghent and University Hospital Ghent, Ghent, Belgium.
5
Department of Pathology, University of Massachusetts Memorial Medical Center, Worcester.
6
Department of Pathology, Sacred Heart Hospital, Negrar.
7
Department of Pathology, Memorial Sloan Kettering Cancer Center, New York.
8
Department of Medical Oncology, Dana Farber Cancer Institute.
9
Department of Pathology, The Jikei University School of Medicine, Tokyo, Japan.
10
Department of Pathology, Catholic University of Sacred Heart, Rome, Italy.
11
Department of Oncology-Pathology, Karolinska Institute.
12
Department of Pathology and Cytology, Karolinska University Hospital, Stockholm, Sweden.
13
Ampath Private Pathology Laboratories and Department of Anatomical Pathology, University of Pretoria, Pretoria, South Africa.
14
Department of Pathology, Stony Brook University Hospital, Stony Brook, NY.
15
Department of Pathology, Massachusetts General Hospital, Boston, MA.

Abstract

Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms that may show overlapping morphology and immunohistochemistry with uterine smooth muscle tumors. In this study, we evaluated the morphologic, immunohistochemical, and molecular features of 32 PEComas, including 11 with aggressive behavior. Two distinct morphologies were observed: classic (n=30) and those with a lymphangioleiomyomatosis appearance (n=2). In the former, patients ranged from 32 to 77 (mean: 51) years and 13% had tuberous sclerosis. Tumors ranged from 0.2 to 17 (mean: 5.5) cm with 77% arising in the corpus. Epithelioid cells were present in 100% and a spindled component was seen in 37%. Nuclear atypia was low (53%), intermediate (17%), or high (30%). Mitoses ranged from 0 to 36 (mean: 6) and 0 to 133 (mean: 19) per 10 and 50 high-power fields, with atypical mitoses present in 30%. Thin and delicate vessels were noted in 100%, clear/eosinophilic and granular cytoplasm in 93%, stromal hyalinization in 73%, necrosis in 30%, and lymphovascular invasion in 10%. All tumors were positive for HMB-45, cathepsin K, and at least one muscle marker, with most expressing melan-A (77%) and/or MiTF (79%). A PSF-TFE3 fusion was identified in one while another showed a RAD51B-OPHN1 fusion. Follow-up ranged from 2 to 175 (mean: 41) months, with 63% of patients alive and well, 20% dead of disease, 13% alive with disease, and 3% dead from other causes. In the latter group (n=2), patients were 39 and 49 years old, one had tuberous sclerosis, while the other had pulmonary lymphangioleiomyomatosis. Both tumors expressed HMB-45, cathepsin K, and muscle markers, but lacked TFE3 and RAD51B rearrangements. The 2 patients are currently alive and well. Application of gynecologic-specific criteria (≥4 features required for malignancy: size ≥5 cm, high-grade atypia, mitoses >1/50 high-power fields, necrosis, and lymphovascular invasion) for predicting outcome misclassified 36% (4/11) of aggressive tumors; thus, a modified algorithm with a threshold of 3 of these features is recommended to classify a PEComa as malignant.

KEYWORDS:

perivascular epithelioid cell tumor; PEComa; uterus; tuberous sclerosis; diagnostic criteria; TFE3; RAD51B

PMID:
30001237
PMCID:
PMC6133752
[Available on 2019-10-01]
DOI:
10.1097/PAS.0000000000001119

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