Abstract P1-08-19: Surgical oncoplastic treatment of a rare case of expansive dermatofibrosarcoma protuberans on the breast

Abstract Background: Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue sarcoma, with low-grade and slow-growing pattern, initiating in the dermis and then invading the subcutaneous tissue, representing less than 0,1% of all malignancies. Its biological behavior is characterized by aggressive local infiltration with high recurrence rate but rarely metastasizes.DFSP normally occurs in middle-aged adults and exhibits a slight male predominance. It corresponds to 6% of all tissue sarcomas and in the breast is extremelly rare. It resembles a keloid or an atrophic lesion like sclero-derma. These features make the early diagnosis difficult. The main treatment is the surgical excision with safe margins up to 3cm extent. Because of this, a wide resection is necessary, usually followed by a oncoplastic technique to minimize aesthect defect. Method: We describe a case of a female patient with an expansive dermatofibrosarcoma protuberans on the left breast, diagnosed after 5 years of progression, with a challenging surgical treatment. Results: A 35-year-old female patient was complaining of a reddish lesion in the left breast with gradually progressive growth for 5 years. There was no history of preceding trauma, surgery, ulceration, papillary discharge, fever or weight loss.The physical examination revealed a light-reddish, delineated nodular cutaneous plaque 7 x 6 cm in the junction of inner quadrant of the left breast. No other finding from the breasts or lymphatic chain was noted. She had an unremarkable personal and family history.She had performed a skin biopsy 1 year before in another service with the following report: “spindle cell injury without atypia in the dermis. The lesion compromises the deep edge of the fragment.”Lesion complete resection with evaluation of intraoperative surgical margins and oncoplastic technique surgery was then indicated for diagnostic elucidation.The intraoperative biopsy report showed a dermis infiltrative spindle cell lesion with atypia and was necessary a wide excision followed by a superior pedicle mastopexy without volume reduction as the patient had requested.The final pathology report confirmed the dermatofibrosarcoma protuberans due to a spindle mesenchymal neoplasm located in the superficial and deep dermis of the breast skin, showing focal extension to the hypodermis, composed of elongated cells with eosinophilic cytoplasm and monomorphic nuclei arranged in a storiform pattern, within a collagenized stroma (figures 1 and 2). Immunohistochemical study was positive for CD34 and negative for Factor XIIIA (figures 3 and 4). Conclusion: In this rare case, the skin location is one of the most challenging sites for reconstruction after de large excision to maintain symmetry. Citation Format: Giovanna Azevedo Gabriele Carlos, Ridania Frederice, Patricia Figueiredo, Karla Prigenzi. Surgical oncoplastic treatment of a rare case of expansive dermatofibrosarcoma protuberans on the breast [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P1-08-19.