Case Report: Integrating Histomorphology and Multi-marker Immunohistochemical Profiling in the Diagnosis of Classic Dermatofibroma: A Clinical Case Report

<ns3:p>Introduction Dermatofibroma (DF), or benign fibrous histiocytoma, is a ubiquitous cutaneous neoplasm. Despite its prevalence, its extensive morphological diversity can create diagnostic gray zones, necessitating a rigorous distinction from aggressive mesenchymal malignancies, most notably dermatofibrosarcoma protuberans (DFSP). Case Presentation A 36-year-old female presented with a slowly enlarging, firm cutaneous mass on the medial thigh. Following a wide local excision, histomorphological evaluation identified a well-circumscribed dermal proliferation of spindle cells arranged in a storiform architecture, characterized by a distinct Grenz zone and peripheral collagen trapping. While sparse focal infiltration into the superficial subcutis was noted, the absence of cytologic atypia and a low mitotic index favored a benign etiology. A multi-marker immunohistochemical (IHC) panel was employed to achieve diagnostic certainty. The lesion exhibited weak, focal CD34 expression restricted to the periphery, alongside focal S100 and D2–40 positivity, effectively ruling out DFSP and neural-derived tumors. The postoperative recovery, supported by standard antibiotic and anticoagulant prophylaxis, was unremarkable. Conclusion This report delineates a comprehensive clinicopathological roadmap for the evaluation of spindle cell lesions. By synthesizing classical morphological landmarks with nuanced IHC profiling, particularly the interpretation of peripheral CD34 and D2–40 expression, clinicians can achieve high diagnostic fidelity. Such an integrated approach is paramount to ensuring favorable clinical outcomes and preventing the excessive surgical morbidity associated with the misdiagnosis of benign fibrohistiocytic variants as high-grade sarcomas.</ns3:p>