Collagenous fibroma

Collagenous Fibroma (also known as Desmoplastic Fibroblastoma) is a rare, benign soft tissue tumor characterized by its abundant collagenous stroma. First described by Evans in 1995, collagenous fibroma presents as a slow-growing, painless mass, most commonly located in the subcutaneous tissues or attached to the fascia or skeletal muscles. Despite its benign nature, its clinical and radiological features can sometimes mimic those of malignant tumors, making accurate diagnosis crucial.

Epidemiology

Collagenous fibroma is a rare entity with no predilection for any specific age group, although most cases have been reported in adults. There is a slight male predominance. The tumor has been identified in various anatomical locations, including the upper and lower extremities, trunk, neck, and head.

Clinical Presentation

Patients with collagenous fibroma typically present with a slow-growing, painless mass. The size of the tumor at presentation can vary, but most are between 2 to 10 cm in diameter. Rarely, patients may report discomfort or pain, which is usually associated with the compression of adjacent structures.

Pathology

Macroscopically, collagenous fibromas are well-circumscribed, lobulated masses with a whitish, firm appearance. Microscopically, they are characterized by a dense, collagenous stroma interspersed with spindle-shaped fibroblasts. Mitotic figures are rare, and there is no evidence of nuclear atypia, which helps in distinguishing them from malignant fibrous tumors.

Diagnosis

The diagnosis of collagenous fibroma is primarily based on histopathological examination. Imaging techniques such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) can be used to assess the extent of the tumor and its relationship with adjacent structures, but they are not definitive for diagnosis. Biopsy or surgical excision of the tumor followed by histological analysis is necessary to confirm the diagnosis.

Treatment and Prognosis

Surgical excision with clear margins is the treatment of choice for collagenous fibroma. The tumor has a very low recurrence rate after complete excision. Malignant transformation has not been reported, and the prognosis is excellent.

Differential Diagnosis

The differential diagnosis for collagenous fibroma includes other benign and malignant soft tissue tumors such as fibromatosis, fibrosarcoma, and myxofibrosarcoma. Histological examination is crucial for accurate diagnosis.

Conclusion

Collagenous fibroma is a rare, benign soft tissue tumor with distinctive histological features. Although it is a benign entity, accurate diagnosis is essential to differentiate it from other soft tissue tumors. Surgical excision is curative, and the prognosis is excellent.

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