Pleomorphic hyalinizing angiectatic tumors (PHAT) of soft parts are locally recurring non-metastasizing neoplasms of intermediate biologic potential and are classified as soft tissue tumors of uncertain lineage.
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Epidemiology
Pleomorphic hyalinizing angiectatic tumors of soft parts a very rare and have been described over a wide age range. The tumors are slightly more frequently seen in women 1,2.
Diagnosis
Pleomorphic hyalinizing angiectatic tumors (PHAT) of soft parts is diagnosed based on typical histological and molecular pathological features.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:
- clusters of ectatic blood vessels encircled by hemosiderin-laden pleomorphic cells with pseudoinclusions
- very few to absent mitoses
- peripheral zones of haemosiderotic fibrolipomatous tumor
The following criterion is desirable:
- TGFBR3 and/or OGA rearrangement
Clinical presentation
Clinically the tumor commonly manifests as a slow-growing or longstanding subcutaneous mass often mimicking vascular tumors such as hemangioma or Kaposi sarcoma 1,2.
Pathology
Pleomorphic hyalinizing angiectatic tumors of soft parts are characterized by ectatic blood vessels surrounded by hyalinizing material and pleomorphic hemosiderin-laden cells 1.
Etiology
The etiology of pleomorphic hyalinizing angiectatic tumors of soft parts is unknown 1.
Location
Pleomorphic hyalinizing angiectatic tumors are most commonly found in the subcutaneous tissues of the lower extremities e.g. the ankle and foot. Rarely they have been described in the deep soft tissues of the perineum, buttock, arm or retroperitoneum 1-3.
Macroscopic appearance
Macroscopically pleomorphic hyalinizing angiectatic tumors of soft parts have been described to show a lobulated form sometimes with cystic or myxoid changes and a tannish-white or maroon cut surface. They have been reported with sizes of 5-10 cm 1,2.
Microscopic appearance
Histologically pleomorphic hyalinizing angiectatic tumors of soft parts are characterized by the following features 1,2:
- clusters of thin-walled ectatic blood vessels amidst fibrin-rich amorphous hyalinizing material and tumor cells
- pleomorphic epithelioid to spindled tumor cells with intracytoplasmatic hemosiderin and nuclear pseudoinclusions
- frequent inflammatory infiltrates
- low mitotic activity
- variably myxoid proliferation at the periphery resembling haemosiderotic fibrolipomatous tumor
Immunophenotype
On immunohistochemistry stains, pleomorphic hyalinizing angiectatic tumors of soft parts usually express CD34 and vimentin 1-4.
Genetics
Similar to haemosiderotic fibrolipomatous tumors, pleomorphic hyalinizing angiectatic tumors of soft parts are associated with rearrangements of the TGFBR3 and or OGA genes 1,2.
Radiographic features
Pleomorphic hyalinizing angiectatic tumors of soft parts have been characterized as lobulated heterogeneous lesions 2-4.
US
Ultrasound findings have been reported as heterogeneously hypoechoic with globular hyperechoic intralesional foci 2.
CT
The CT appearance has been described as ill-defined inhomogeneous with heterogeneous enhancement and possible feeding artery 2,3.
MRI
The MRI appearance of pleomorphic hyalinizing angiectatic tumors has been reported to be heterogeneous masses 2-4.
Signal characteristics
- T1: heterogeneously isointense to muscle with multiple hypointense and hyperintense foci
- T2: heterogeneously hyperintense with flow voids
- STIR/PDFS: heterogeneously hyperintense with flow voids
- T1C+ (Gd): heterogeneous enhancement
Nuclear medicine
Pleomorphic hyalinizing angiectatic tumors of soft parts have been reported to show a mild uptake of FDG 2.
Radiology report
The radiological report should include a description of the following:
- form, location and size
- tumor margins and transition zone
- relations to the muscular fascia
- relation to adjacent neurovascular structures
- relations to bones
Treatment and prognosis
The main treatment of pleomorphic hyalinizing angiectatic tumors consists of wide surgical excision 1,2. Up to 50% of the resected lesions show local recurrence which can be usually cured by re-excision. In extremely rare situations, pleomorphic hyalinizing angiectatic tumors of soft parts have been reported to progress to myxoid sarcoma but the exact relationship is unclear 1.
History and etymology
Pleomorphic hyalinizing angiectatic tumors of soft parts have been first described by the British pathologists, Mark E Smith and Cyril Fisher and the American pathologist Sharon Ann Whelan Weiss in 1996 2-5.
Differential diagnosis
Tumors or conditions which can mimic the presentation and/or appearance of pleomorphic hyalinizing angiectatic tumors include 2,5:
- haemosiderotic fibrolipomatous tumor
- angiosarcoma
- Kaposi sarcoma
- malignant fibrous histiocytoma
- schwannoma
- subcutaneous metastases
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