Soft tissue

Uncertain differentiation

Pleomorphic hyalinizing angiectatic tumor


Resident / Fellow Advisory Board: Erna Forgó, M.D.
Deputy Editor-in-Chief: Borislav A. Alexiev, M.D.
Raul Perret, M.D., M.Sc.

Last author update: 11 November 2021
Last staff update: 15 November 2021

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PubMed Search: Pleomorphic hyalinizing angiectatic tumor

Raul Perret, M.D., M.Sc.
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Cite this page: Perret R. Pleomorphic hyalinizing angiectatic tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuephat.html. Accessed August 14th, 2022.
Definition / general
  • Rare and underrecognized soft tissue tumor of intermediate malignancy (locally aggressive) characterized by the presence of pleomorphic cells, low mitotic activity, ectatic blood vessels with damaged walls and no necrosis
Essential features
  • Soft tissue tumor of intermediate malignancy (locally aggressive), with no metastatic potential
  • Characterized by the presence of pleomorphic cells, low mitotic activity, ectatic blood vessels with damaged walls and no necrosis
  • Most cases are positive for CD34 and lack expression of S100, desmin, pankeratin and STAT6
  • Recommended treatment is complete surgical excision with negative margins
Terminology
  • Initially characterized by Smith et al. as pleomorphic hyalinizing angiectatic tumor of soft parts (Am J Surg Pathol 1996;20:21)
  • Controversial terminology: early pleomorphic hyalinizing angiectatic tumor (also known as hemosiderotic fibrolipomatous tumor) is considered in the spectrum of pleomorphic hyalinizing angiectatic tumor (PHAT) by some experts (Am J Surg Pathol 2004;28:1417)
ICD coding
  • ICD-O: 8802/1 - pleomorphic hyalinizing angiectatic tumor
  • ICD-11: 2F7C & XH2193 - neoplasms of uncertain behavior of connective or other soft tissue and pleomorphic hyalinizing angiectatic tumor
Epidemiology
  • Exact epidemiology is uncertain due to the controversial diagnostic criteria and the lack of contemporary series
  • Most cases seem to affect adults (median 51 years, range 10 - 79 years), with a slight female predominance (Am J Surg Pathol 2004;28:1417)
Sites
  • Most arise in the superficial soft tissues of the distal lower extremities, particularly the leg, ankle and foot (Am J Surg Pathol 2004;28:1417)
  • Other areas of the body rarely affected include upper extremities, trunk and head and neck
  • Visceral or intracavitary locations have not been thoroughly documented
Pathophysiology
  • Currently unknown
Etiology
  • Currently unknown
Clinical features
Diagnosis
  • Imaging features are poorly characterized, diagnosis depends on histologic findings and molecular features (selected cases)
Radiology description
  • Imaging findings are poorly characterized and nonspecific (Oncol Lett 2018;15:4720)
  • MRI:
    • Well circumscribed to infiltrative lesions with heterogeneous T1 and T2 signal intensity
    • Heterogeneous contrast enhancement
  • Ultrasound:
    • Hypoechoic lesions with internal punctate hyperechogenic areas
Radiology images

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MRI: buttock mass MRI: buttock mass

MRI: buttock mass

Ultrasound: buttock mass

Ultrasound: buttock mass

Prognostic factors
Case reports
Treatment
Clinical images

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Intraoperative: hand mass

Intraoperative: hand mass

Gross description
  • Well circumscribed to infiltrative masses with tan to maroon cut surfaces (Am J Surg Pathol 1996;20:21)
  • Cystic, gelatinous or hemorrhagic areas can be present
Gross images

Contributed by Raul Perret, M.D., M.Sc.
Breast mass

Breast mass

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Raul Perret, M.D., M.Sc.
Ectatic and thrombosed vessels

Ectatic and thrombosed vessels

Hemosiderin

Hemosiderin

Damaged vessels and pleomorphic cells

Damaged vessels and pleomorphic cells

Inflammatory infiltrate

Inflammatory infiltrate

Nuclear pleomorphism

Nuclear pleomorphism


Intranuclear pseudoinclusion

Intranuclear pseudoinclusion

Virocyte-like cell

Virocyte-like cell

CD34 expression

CD34 expression

Desmin expression

Desmin expression


Relatively well circumscribed lesion

Relatively well circumscribed lesion

Ectactic blood vessels and pleomorphic cells

Ectactic blood vessels and pleomorphic cells

Pleomorphic cells

Pleomorphic cells

CD34

CD34 expression

Virtual slides

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Left foot mass Left foot mass

Left foot mass

Cytology description
  • Tumor cells of varying size and shape with pleomorphic nuclei, pseudoinclusions and intracytoplasmic hemosiderin pigment (Diagn Cytopathol 2015;43:407)
  • Cytological findings alone are nonspecific and should not be used for diagnostic confirmation
Positive stains
Negative stains
Electron microscopy description
  • Bizarre nuclei, nuclear cytoplasmic inclusions and no intercellular junctions
  • Abundant cytoplasmic intermediate filaments and granular endoplasmic reticulum network (Ultrastruct Pathol 2006;30:59)
Molecular / cytogenetics description
Videos

PHAT: pleomorphic hyalinizing angiectatic tumor

Sample pathology report
  • Knee mass, excision:
    • Pleomorphic hyalinizing angiectatic tumor (see comment)
    • Comment: Microscopic examination reveals a relatively well circumscribed lesion with jagged borders centered in the hypodermis. The lesion comprises sheets and fascicles of spindle and pleomorphic cells associated with hemosiderin deposits and clusters of variably thrombotic and ectatic blood vessels. The tumor cells have hyperchromatic nuclei, which are irregular in size and shape. Mitotic activity is low and tumor necrosis is absent. Immunohistochemically, the tumor cells are positive with CD34 and negative with S100, pancytokeratin, MDM2 and STAT6.
    • These histological and immunohistochemical findings are in keeping with pleomorphic hyalinizing angiectatic tumor. If incompletely excised, these intermediate malignancy mesenchymal tumors tend to recur locally, while distant spread is not typically seen.
Differential diagnosis
Board review style question #1

A 53 year old woman presented with a knee mass that had been evolving for 2 years. Histology shows a relatively well circumscribed hypodermal mass composed of bizarre looking pleomorphic cells and abundant clusters of ectatic blood vessels with damaged walls. Mitotic activity is very low (< 1/10 high power fields) and necrosis is absent. On immunohistochemistry, the tumor cells stain for CD34, while S100, pancytokeratin, MDM2 and STAT6 are negative. Which of the following is most likely the correct diagnosis?

  1. Atypical dermatofibroma
  2. Dermatofibrosarcoma protuberans
  3. Pleomorphic hyalinizing angiectatic tumor
  4. Solitary fibrous tumor
  5. Undifferentiated pleomorphic sarcoma
Board review style answer #1
C. Pleomorphic hyalinizing angiectatic tumor

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Reference: Pleomorphic hyalinizing angiectatic tumor
Board review style question #2
Which of the following is true about pleomorphic hyalinizing angiectatic tumor (PHAT)?

  1. Desmin is usually diffusely and strongly positive
  2. It is an intermediate malignancy tumor (locally recurring)
  3. Mitotic rate is generally high
  4. Most cases show sarcomatous transformation
  5. OGA (MGEA5) or TGFBR3 rearrangements are present in all cases
Board review style answer #2
B. It is an intermediate malignancy tumor (locally recurring)

Comment Here

Reference: Pleomorphic hyalinizing angiectatic tumor
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