case_images: PMC11743858_01
case_images: Clinical appearance of the lesion and defects following surgical intervention and subsequent reconstruction. A, On initial presentation, clinical examination revealed a 1.5 cm firm nodule on the right pretibial shin. B, The lesion recurred at the same site 18 months after excisional biopsy. C, A 4.9 cm surgical defect after the second stage of Mohs micrographic surgery, which was halted due to positive deep margins in fascia overlying tibialis anterior muscle. D, A 10 cm surgical defect following radical resection of the sarcoma with clear margins obtained. E, Surgical site 16 weeks following reconstruction, which consisted of a bipedicle flap with a split-thickness skin graft from the right thigh and the medial portion of the defect healing by second intention.
case_images: gr1.jpg
case_images: PMC11743858_01_gr1.jpg
case_images: fig1
case_images: Physical examination revealed a 1.5 cm firm, round, skin-colored subcutaneous nodule (Fig 1). Given the high recurrence rate associated with cellular dermatofibromas, as well as the rapid regrowth and large size of the lesion, the patient underwent surgical removal with Mohs micrographic surgery; however, the procedure was halted after the second stage due to positive deep margins in the fascia overlying the tibialis anterior muscle (Fig 1). Following multidisciplinary discussions, she underwent neoadjuvant radiation (total dose of 50 Gy) followed by radical resection of the sarcoma by surgical oncology with clear margins 3 months after Mohs surgery (Fig 1). A portion of the defect was left to heal by second intention (Fig 1).
case_images: Histologic features from the cellular dermatofibroma and high-grade sarcoma. A and B, The cellular dermatofibroma consists of a deep dermal proliferation of cytologically bland spindled and histiocytoid cells arranged in a vaguely storiform pattern and with peripheral collagen trapping and subtle basal layer hyperpigmentation (H&E-stained slides, 20x magnification and 400x magnification, respectively). C, Tumor cells are without staining for CD34. Background vessels show variable staining (CD34 immunostain, 200x magnification). The tumor cells were also negative for desmin, SOX10, and HMB-45 immunostains (slides not shown). D, The high-grade sarcoma consists of a dense, infiltrative dermal and subcutaneous proliferation of cytologically atypical cells arranged in a variably fascicular and storiform pattern (H&E-stained slide, 20x magnification). E, The sarcoma cells are spindled in morphology and cytologically atypical with nuclear hyperchromasia and coarse chromatin. A mitotic figure is highlighted with the yellow arrow (H&E-stained slide, 400x magnification). F, Residual peripheral collagen trapping is present (H&E-stained slide, 200x magnification). The cells diffusely expressed alpha-SMA but were negative for desmin, SOX10, S100, AE1/AE3, CAM5.2, p63, and CD34 immunostains (slides not shown).
case_images: gr2.jpg
case_images: PMC11743858_01_gr2.jpg
case_images: fig2
case_images: The patient underwent an excisional biopsy 3 months after initial presentation, with histopathologic evaluation revealing a cellular dermatofibroma present at the specimen margins (Fig 2). The tumor was sent for histopathologic evaluation, revealing a high-grade sarcoma within the cellular dermatofibroma (Fig 2).