CASE 10807 Published on 26.03.2013

Paraaortic PEComa

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Rossi P, Raffo L, Quaglia FM, Vitali S, Novaria L, Caramella D, Bartolozzi C.

Ospedale Santa Chiara,
Pisa; Via Roma 6, 56125 Pisa, Italy;
Email:rossi-piercarlo@live.it
Patient

68 years, female

Categories
Area of Interest Abdomen, Arteries / Aorta ; Imaging Technique CT
Clinical History
A 68-year-old female patient came to our department with loss of appetite, weakness, persistent low-grade fever and weight loss. Previous blood tests were normal.
Imaging Findings
An ultrasound of the abdomen, performed elsewhere, showed in the left hemiabdomen below a plane passing through the transverse umbilical line two contiguous tumefactions (diameter 10mm and 50mm) within the mesenteric fan.
CT examination (Fig.1) confirmed the presence of a parenchymatous, inhomogeneous, retroperitoneal tumour of pathological aspect, with heterogeneous contrast enhancement.
The patient underwent surgery to remove the tumour and histological analysis of the surgical specimen revealed the presence of a malignant (for high mitotic count, size and presence of necrosis) pT2BNxMxG3 PEComa.
After surgery the patient began adjuvant chemotherapy with sunitinib.
After 3 months of therapy (fig.2), a CT showed no recurrence of disease.
Discussion
The World Health Organization defines perivascular epithelioid cell tumours (PEComas) as "mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells (PECs)" [1].
In literature 100 cases of PEComa have been referred, most of them uterine (other common sites are vulva, rectum, liver, retroperitoneum, but these tumours may potentially arise from any anatomic location), PEComas are often related to the tuberous sclerosis [2].This tumour does not have a normal counterpart, the clinical history is unpredictable and it mainly affects young people or women because hormones seem to play a role (immunohistochemistry is often positive for oestrogen and progesterone receptor) [3].
There are hypotheses that PEComas arise either from neural crest cells or myoblasts or pericytes [4]. PEComas may affect different anatomical sites and clinical manifestations depend on the location of the tumour. Symptoms, when present, are nonspecific, mainly abdominal pain, weakness, bleeding, fever. Imaging findings are often non-specific too: CT and ultrasound detects masses, but are uninformative about the nature of the tumour, however, these techniques may be used to guide the biopsy. Diagnosis of PEComa is made by histologic examination of the biopsy sample or surgical specimen [5].
Histological analysis of PEComa reveals alveolar architecture tumour with epithelioid or spindle cells, clear, granular and hyper chromatic cytoplasm, nuclear pleomorphism and atypical mitoses, necrosis, vascular emboli and a perivascular distribution.
Immunoistochemical profile demonstrates positive staining for myoid markers: vimentin, desmin, smooth muscle actin, CD-99 and melanocytic markers: HMB-45 (positive in 100% of known cases), Melan A (Mart-1) [6].
Most PEComas have a benign clinical course. An increasing number of malignant PEComas are reported in the literature. In 2005 Folpe [7] suggested three criteria of malignancy: size > 8 cm, mitotic count greater than 1/50 hig power fields and necrosis. Also infiltrative growth, hypercellularity, hyperchromasia, nucleomegaly, multinucleation atypical mitotic figures could be considered as malignant features [8].
Treatment of choice, the only one capable to eradicate the disease, is wide surgical resection for both primary tumour, metastases and local recurrence. Radiotherapy and chemotherapy to date have not demonstrated benefits [9], encouraging results were seen in a study using mTOR inhibitor as adjuvant therapy [10].
Differential Diagnosis List
Retroperitoneal paraaortic PEComa
Melanoma
Gastrointestinal stromal tumour (GIST)
Adipocytic tumour
Clear cell sarcoma
Leiomyosarcoma
Final Diagnosis
Retroperitoneal paraaortic PEComa
Case information
URL: https://www.eurorad.org/case/10807
DOI: 10.1594/EURORAD/CASE.10807
ISSN: 1563-4086