A masquerading presentation of dermatofibrosarcoma protuberans

A 53-year-old man with a history of basal cell carcinoma presented with an asymptomatic lesion on his chest that was initially evaluated in March 2022 and clinically diagnosed as a cyst. Due to increased growth, the patient opted for surgical excision. A targeted review of the systems was negative for constitutional, musculoskeletal, and cardiopulmonary symptoms. A physical examination demonstrated a well-defined, subcutaneous tumor measuring approximately 3.3 cm without any overlying surface changes on his sternum (Figure 1A [red star] and Figure 1B). Histology revealed monotonous spindle cells arranged in a storiform pattern (Figure 2A, black arrow) with infiltration of the subcutaneous fat (Figure 2A, red arrow). Immunohistochemical (IHC) stains were performed and showed diffuse positivity to CD34 (Figure 2B). Conversely, SOX-10 and Factor XIIIa were both negative. Despite its benign clinical presentation, histopathology confirmed the diagnosis of dermatofibrosarcoma protuberans (DFSP). The patient was referred to medical and surgical oncology for further management and underwent a wide local excision (WLE) with negative margins. He currently follows with Dermatology for ongoing clinical follow-up every six months.

Figure 1:

Physical examination and pre-surgical outline. (A) Physical examination demonstrating subcutaneous tumor on the patient’s superior medial chest, indicated by the red star. (B) A subcutaneous tumor outlined with a gentian violet skin marker prior to surgical excision.

Figure 2:

Histology with associated immunohistochemistry. (A) Dense proliferation of monotonous spindle cells arranged in a storiform pattern, indicated by the black arrow, with characteristic honeycomb infiltration of subcutaneous fat, as noted by the red arrow (hematoxylin and eosin, 10×). (B) Diffuse positivity of immunohistochemical (IHC) stain CD34 (CD34, 10×).

DFSP is a rare dermal sarcoma characterized by high rates of recurrence and low metastatic potential. It presents as an asymptomatic, flesh-colored, indurated plaque that develops a multinodular appearance typically on the trunk and proximal extremities, most commonly in middle-aged adults [1]. Our case highlights an atypical presentation because it was initially diagnosed as a cyst and lacked the protuberant configuration. Given its nonspecific clinical appearance, the clinical differential is broad and may include neurofibromas, leiomyomas, cysts, keloids, nonmelanoma skin cancer, Kaposi’s sarcoma, dermatofibroma, and sarcoidosis [1]. DFSP is characterized by a unique translocation t(17;22)(q22;q13) resulting in a fusion gene of COL1A1-PDGFβ. This is present in 90 % of patients and leads to constitutively active tyrosine-kinase activity promoting tumorigenesis [2, 3]. Although clinical risk factors have not been fully delineated in the literature, DFSP has been reported to be associated with prior trauma or scars [4]. A biopsy with additional IHC staining is the gold standard for diagnosis. DFSP is typified by a storiform pattern of uniform, spindled cells that infiltrate the subcutaneous tissue in a “honeycomb” pattern [1], [2], [3]. The classic IHC staining pattern of DFSP is CD34-positive and Factor XIIIa-negative. Historically, both Mohs micrographic surgery and WLE were utilized to achieve tumor clearance as the initial curative treatment [1, 2, 5, 6]. Most recently, the National Comprehensive Cancer Network (NCCN) has updated its guidelines to recommend Mohs over WLE as the preferred surgical modality given the lower rates of local recurrence between the two [6, 7]. A perioperative MRI with contrast may be considered if extensive subcutaneous extension is suspected [7]. Solitary DFSP is the most common presentation; however, this sarcoma can metastasize most frequently to the lungs, albeit at low rates between 0.5 and 5 % [1, 3]. Although metastatic spread is extremely rare, for patients with high-risk features (e.g., fibrosarcomatous change) or patients who have undergone extensive surgery, the NCCN currently recommends an MRI with contrast to detect any metastatic spread [7]. The NCCN also recommend ongoing clinical follow-up with focus on the primary site every 6–12 months [7]. For those patients with unresectable, advanced, or metastatic disease, imatinib mesylate, a tyrosine kinase inhibitor, can be utilized [8].