Superficial primitive neuroectodermal tumor/Ewing sarcoma (PN/ES): same tumor as deep PN/ES or new entity?

Area of Science:

• Oncology
• Dermatopathology
• Molecular Pathology

Background:

• Primitive neuroectodermal tumor/Ewing sarcoma (PN/ES) typically affects bone and deep soft tissues in young males.
• Dermal or cutaneous PN/ES is exceptionally rare, with limited case reports.
• Understanding the characteristics of dermal PN/ES is crucial for accurate diagnosis and treatment.

Purpose of the Study:

• To investigate the clinicopathologic features of primary cutaneous primitive neuroectodermal tumor/Ewing sarcoma.
• To compare the behavior and prognosis of dermal PN/ES with conventional deep-seated PN/ES.
• To identify potential unique genetic abnormalities in cutaneous PN/ES.

Main Methods:

• Retrospective review of consultation files for cases coded as dermal, cutaneous, or skin PN/ES.
• Inclusion of only primary dermal cases with complete diagnostic material.
• Histopathological, immunohistochemical (CD99, Fli-1, etc.), and reverse transcription-polymerase chain reaction analyses were performed.

Main Results:

• Thirteen primary dermal PN/ES cases were identified, predominantly in women (10/13) with a mean age of 28 years.
• Tumors were superficial, small (0.5-2.3 cm), often painful, and located in various cutaneous sites.
• Histopathology showed small round to oval cells with characteristic CD99 reactivity; one case had EWS-Fli-1 translocation. Prognosis appeared better than deep PN/ES, with one metastasis and death at 3 years among 11 followed cases.

Conclusions:

• Cutaneous PN/ES is a distinct entity presenting as a superficial tumor, primarily in adult women.
• Dermal PN/ES exhibits a more favorable prognosis than its deep-seated counterpart.
• Further research into potential unique genetic alterations in cutaneous PN/ES is warranted.