Encyclopedia of Pathology

Living Edition
| Editors: J.H.J.M. van Krieken

Pleomorphic Fibroma

  • Thomas BrennEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-28845-1_5452-1
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Definition

Pleomorphic fibromas are benign polypoid stromal proliferations containing bizarre appearing and often multinucleated cells.

Clinical Features

  • Incidence

    Rare but no accurate data exist on incidence.

  • Age

    There is a predilection for middle-aged adults (Kamino et al. 1989).

  • Sex

    Females are slightly more frequently affected than males.

  • Site

    The extremities are most commonly affected followed by the trunk (Kamino et al. 1989).

  • Treatment

    No specific treatment is necessary and simple excision is curative.

  • Outcome

    Pleomorphic fibromas are benign.

Macroscopy

Pleomorphic fibroma presents as solitary, flesh-colored, dome-shaped papules or polypoid nodules measuring few millimeters up to 1.5 centimeters (Kamino et al. 1989).

Microscopy

Pleomorphic fibromas are nodular or polypoid dermal-based tumors containing scattered large, spindled to stellate cells in a collagenous stroma (Fig. 1). The tumor cells contain pleomorphic and hyperchromatic nuclei. Multinucleated forms are common (Fig. 2). The tumors are paucicellular and the stromal collagen bundles are haphazardly distributed. Focal stromal myxois change may also be encountered.
Fig. 1

Paucicellular dermal-based tumor composed of scattered hyperchromatic stellate cells in a stromal background containing haphazardly distributed collagen bundles and ectatic vessels

Fig. 2

The tumor cells are stellate and contain hyperchromatic nuclei. Multinucleated forms are common

Immunophenotype

The tumor cells express CD34 with loss of RB1 expression. There is variable SMA expression.

Molecular Features

Deletion of RB1 on chromosome 13q but no amplification of MDM2 (Al-Zaid et al. 2013; Hinds et al. 2017).

Differential Diagnosis

The tumors closely resemble pleomorphic lipoma but lack the adipocytic component.

References and Further Reading

  1. Al-Zaid, T., Wang, W. L., Lopez-Terrada, D., Lev, D., Hornick, J. L., Hafeez Diwan, A., Fletcher, C. D., & Lazar, A. J. (2013). Pleomorphic fibroma and dermal atypical lipomatous tumor: Are they related? Journal of Cutaneous Pathology, 40(4), 379–384.CrossRefGoogle Scholar
  2. Hinds, B., Agulló Pérez, A. D., LeBoit, P. E., McCalmont, T. H., & North, J. P. (2017). Loss of retinoblastoma in pleomorphic fibroma: An immunohistochemical and genomic analysis. Journal of Cutaneous Pathology, 44(8), 665–671.CrossRefGoogle Scholar
  3. Kamino, H., Lee, J. Y., & Berke, A. (1989). Pleomorphic fibroma of the skin: A benign neoplasm with cytologic atypia. A clinicopathologic study of eight cases. The American Journal of Surgical Pathology, 13(2), 107–113.CrossRefGoogle Scholar

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Authors and Affiliations

  1. 1.Department of Pathology and Laboratory Medicine and The Arnie Charbonneau Cancer InstituteCumming School of Medicine, University of CalgaryCalgaryCanada