Benign fibrous histiocytoma arising from the intercostal space

Subcutaneous dermatofibroma: a rare case report with review of literature

A purely Sub-cutaneous benign fibrous histiocytoma (BFH; dermatofibroma) is rarely reported, as it is usually a dermally located mesenchymal tumour and in absence of supportive immunohistochemical (IHC) studies, it is often misdiagnosed. We are describing a case of a 19-year-old female who presented to the skin outpatient department with a painful swelling on the medial side of her thigh. Fine needle aspiration (FNA) revealed a sub-cutaneous spindle cell (mesenchymal) lesion which was corroborated on histopathology, with differentials of BFH and dermatofibrosarcoma protruberans (DFSP). BFH constitutes a diagnostic dilemma for both clinicians and pathologists, because the lesions share common clinical symptoms, radiological characteristics and histological features with many varied entities. For its subtyping and confirmation; immunohistochemical (IHC) studies were undertaken. In the present case, positivity of IHC markers, vimentin and smooth muscle actin emphatically proved that BFH arose exclusively from the subcutaneous region, with no dermal origin. Also, a negative CD34 immunostaining, along with low B-cell lymphoma 2 (Bcl-2) expression ruled out DFSP (both are strongly expressed in DFSP), MFH and other malignant mesenchymal lesions. Negative CD 68 staining ruled out giant cell lesions and their congeners. This case is worth reporting, as it not only describes a rare case presentation of BFH, but as it also highlights the importance of IHC, thus helping to comprehensively clinch the diagnosis by systematically ruling out other differentials.

Benign fibrous histiocytoma arising from the right shoulder: Is immunohistochemical staining always required for a definitive diagnosis?

INTRODUCTION

Fibrous histiocytomas are divided into two subgroups: malignant and benign fibrous histiocytomas (BFHs). BFH is one of the most common tumors of the superficial and deep soft tissues; it is commonly found on the skin and presents as a slow-growing solitary nodule made up of a mixture of fibroblastic and histiocytic cells.

PRESENTATION OF CASE

In this study, we present the case of a 45-year-old female who was histopathologically diagnosed with dermatofibrosarcoma protuberans (DFSP) and received radiotherapy, but whose diagnosis was changed to BFH based on subsequent immunohistochemical analyses.

DISCUSSION

BFH is a mesenchymal soft-tissue tumor with fibroblastic and histiocytic differentiation. Differential diagnosis for BFH found in deeper tissues includes other aggressive fibrohistiocytic lesions, such as DFSP and malignant fibrous histiocytoma. Differentiating among these tumors is crucial in selecting the correct surgical strategy and patient management in the postoperative period. In most cases, the pleomorphism and atypical mitotic activity seen histopathologically are sufficient for the differentiation between benign and malignant tumors. Immunohistochemical staining methods should be used in cases that are difficult to diagnose. The treatment of choice for BFH is wide resection of the tumor, which results in an excellent prognosis and low recurrence rate. In agreement with cases reported in the literature, our case confirms that wide excision is adequate to prevent the recurrence of the tumor.

CONCLUSION

Although benign fibrous histiocytomas is rare, it must be considered in the differential diagnosis of tumors arising from the soft-tissue.