Pleomorphic fibroma of the skin with MDM2 immunoreactivity: A potential diagnostic pitfall

Atypical fibrous histiocytomas and pleomorphic fibroma-type lesions in a patient with li-fraumeni syndrome

Atypical fibrous histiocytomas are an uncommon but benign variant of dermatofibroma where the neoplastic cells can feature cytological atypia constituted by prominent nuclear enlargement, pleomorphism and multinucleated giant cells. Though these can have a degree of atypia, they have a benign course and a failure to recognize these tumors as benign can lead to misdiagnosis and overtreatment, particularly in patients with Li-Fraumeni syndrome who are known to be predisposed to various malignancies. Here, we report a patient with atypical fibrous histiocytomas and multiple pleomorphic fibroma-type lesions in the setting of Li-Fraumeni syndrome.

Pleomorphic Fibroma Presenting as a Nodular Lesion in the Left Shoulder: A Case Report

Pleomorphic fibroma is an uncommon benign cutaneous tumor that often presents as a single asymptomatic skin-colored lesion with indefinite clinical diagnostic features. Here, we report a case of a 47-year-old female diagnosed with pleomorphic fibroma of the skin in the left shoulder and discuss the importance of immunohistochemistry and special features in histopathology to distinguish some of the differentials.

Pleomorphic Fibroma: A Clinicopathologic Case Series With the Review of the Literature

BACKGROUND

Pleomorphic fibromas are rare flesh-colored benign neoplasms first described in 1989. Their histopathology is notable for nuclear pleomorphism of spindle cells and multinucleate giant cells but lacking mitoses. The cellular origin of these tumors is unknown. This case series describes an additional 18 lesions with discussion of histopathology and immunohistochemistry.

METHODS

This case series of 18 pleomorphic fibromas uses immunohistochemical staining for CD34, CD68, factor XIIIa, and S-100 and general histopathologic examination under light microscopy to describe the lesions.

RESULTS

Immunohistochemical stains for CD34 showed nearly universal positivity of the pleomorphic spindle cells, although some more focally. The pleomorphic cells were negative for CD68, variably positive for factor XIIIa, and universally negative for S-100. All the lesions showed characteristic nuclear pleomorphism with absent mitoses. Collagen thickening was variable, mucin was absent, and perivascular inflammation was present in all lesions.

CONCLUSIONS

Pleomorphic fibromas are fibrous lesions with benign clinical course and histopathologic findings including nuclear pleomorphism. Immunohistochemical staining characteristics of the lesion, along with unique spindle cells and multinucleate giant cells help to differentiate this from other tumors.