Giant dermatofibroma: a case report and the review of the literature.

Dermatofibroma is a benign cutaneous tumor that generally ranges in size from 1 to 3 cm in diameter. However, these tumors sometimes become bigger and may be misdiagnosed as a malignant tumor. In this report, we demonstrate a case of giant dermatofibroma (GDF) and review similar cases in the literature. A 20-year-old man presented with a 3-year history of a slowly growing nodule on his lower right leg. Physical examination revealed a brownish, firm nodule, which was 5 cm in diameter and immobile due to subcutaneous tissue adhesion. MRI imaging suggested an invasion close to the fascia of the anterior tibial muscle. An initial incisional biopsy showed a dense irregularly arranged fibroblast proliferation throughout the dermis and superficial subcutaneous tissue, suggesting dermatofibrosarcoma protuberans. For both diagnosis and therapeutic purposes, we performed a simple surgical excision. Histopathological examination revealed a relatively sparse proliferation of fibroblasts without nuclear atypia that produced mature collagen bundles throughout the entire tumor. Immunohistological examination showed a lack of CD34 expression in the proliferative fibroblasts, leading to the diagnosis of GDF. GDF is an unusual dermatofibroma variant, usually exceeding 5 cm in diameter (Requena et al, JAAD 30: 714–719, 1994) that preferentially develops on the lower legs. Due to its clinical and histopathological characteristics, its distinction from malignant tumors is problematic. In our case, using the initial small biopsy specimen we failed to reach the correct diagnosis, and an excisional biopsy was required. According to the literature, GDF invariably has a benign clinical course and a simple excision is curative. However, an excisional biopsy of the whole tumor is recommended because of the diagnostic difficulties due to its clinical and histopathological appearance. [ABSTRACT FROM AUTHOR]