Accuracy rate for clinical diagnosis of dermatofibroma in patients referred to dermatology and pathology department of Emam Reza hospital

Considering its typical clinical manifestation, Dermatofibroma [DF] can be clinically diagnosed in most cases. It has been nevertheless, common practice to rely on pathologic diagnoses. We decided to estimate the rate of correct clinical diagnosis and also the relative importance of other lesions in differential diagnosis of DF. We studied archived biopsies in Dermatology and Pathology Department of Emam Reza hospitals from 1984 until 1 2004 and Dermatofibroma cases were selected, then slides were reviewed. Demographic and other relevant data such as age, sex, etc were gathered and analysed. Eighty two of 127 clinically diagnosed dermatofibroma cases were confirmed by histologic examination [positive predictive value 64.5%]. The most common histological diagnosis in the remaining 45 cases were nodular hidradenoma [7 cases] and comedon and epidermal cyst [11 cases collectively]. In addition, 32 cases of histologically diagnosed dermatofibroma were found with different clinical diagnosis. According to our data, the sensitivity of clinical diagnosis was 72%. It was also found that the lesion is more common in females [57%] and in extremities [58%]. It often appears as a nodular [72%] lesion measuring 5 to 15 millimeters. Histopathologic examination is important for diagnosis of Dermatofibroma. According to our data, the probabilities of false positive and false negatives were 35.5% and 28%, respectively, which is equivalent to 64.5% positive predictive value [PPV]