Dermatofibroma: sonographic findings and pathologic correlation

Ultrasound of Benign Cutaneous Tumors and Pseudotumors: The Key Lesions

Benign cutaneous tumors are commonly seen in daily practice. Most of these lesions are diagnosed based on clinical appearance, but in some cases, clinical findings are nonspecific. A diagnostic imaging exam is indicated to provide additional information, and the first choice for studying dermatologic lesions is a high-frequency color Doppler ultrasound, a noninvasive technique that can play a relevant role in all cases and give important anatomical information for final diagnosis and proper clinical management. This article aims to show the most common benign skin lesions emphasizing clinical-sonographic correlation and familiarizing radiologists with the sonographic appearance of the key benign cutaneous tumors.

High-Frequency Ultrasound Imaging to Distinguish High-Risk and Low-Risk Dermatofibromas

BACKGROUND

Dermatofibroma has various pathological classifications, some of which pose a risk of recurrence and metastasis. Distinguishing these high-risk dermatofibromas based on appearance alone can be challenging. Therefore, high-frequency ultrasound may provide additional internal information on these lesions, helping to identify high-risk and low-risk dermatofibroma early.

METHODS

In this retrospective study, 50 lesions were analyzed to explore the correlation between clinical and high-frequency ultrasound features and dermatofibroma risk level. Based on their pathological features, the lesions were divided into high-risk (n = 17) and low-risk (n = 33) groups. Subsequently, an identification model based on significant high-frequency ultrasound features was developed.

RESULTS

Significant differences were observed in the thickness, shape, internal echogenicity, stratum basal, and Doppler vascular patterns between the high-risk and low-risk groups. The median lesion thickness for the high-risk dermatofibroma group was 4.1 mm (IQR: 3.2-6.1 mm), while it was 3.1 mm (IQR: 1.3-4.2 mm) for the low-risk dermatofibroma group. In the high-risk dermatofibroma group, irregular morphology was predominant (70.6%, 12/17), the most common being dermis-to-subcutaneous soft tissue penetration (64.7%, 11/17), and heterogenous internal echogenicity was observed in the majority of cases (76.5%, 13/17). On the other hand, regular morphology was more prevalent in the low-risk dermatofibroma group (78.8%, 26/33), primarily limited to the dermis layer (78.8%, 26/33), with homogeneous internal echogenicity also being prevalent in the majority of cases (81.8%, 27/33). Regarding the Doppler vascularity pattern, 69.7% (23/33) of low-risk dermatofibromas had no blood flow, while 64.7% (11/17) of high-risk dermatofibromas had blood flow.

CONCLUSION

High-frequency ultrasound is crucial in distinguishing high-risk and low-risk dermatofibromas, making it invaluable for clinical management.

Challenging Patterns of Atypical Dermatofibromas and Promising Diagnostic Tools for Differential Diagnosis of Malignant Lesions

Dermatofibroma (DF) or fibrous histiocytoma is one of the most frequent benign cutaneous soft-tissue lesions, characterized by a post-inflammatory tissue reaction associated with fibrosis of the dermis. Clinically DFs have a polymorphous clinical aspect from the solitary, firm, single nodules to multiple papules with a relatively smooth surface. However, multiple atypical clinicopathological variants of DFs have been reported and, therefore, clinical recognition may become challenging, leading to a more burdensome identification and sometimes to misdiagnosis. Dermoscopy is considered an important tool in DFs diagnosis, as it improves diagnostic accuracy for clinically amelanotic nodules. Although typical dermoscopic patterns are most frequently seen in clinical practice, there have also been some atypical variants described, mimicking some underlying recurrent and sometimes harmful skin afflictions. Usually, no treatment is required, although an appropriate work-up may be necessary in specific cases, such as in the presence of atypical variants or a history of recent changes. This narrative review's aim is to summarize current evidence regarding clinical presentation, positive and differential diagnosis of atypical dermatofibromas and also to raise awareness about the importance of specific characteristics of atypical variants to better differentiate them from malignant conditions.

Role of ultrasound in the diagnosis of primary and recurrent dermatofibrosarcoma protuberans

BACKGROUND

Dermatofibrosarcoma protuberans (DFSP) is a rare, low- to intermediate-grade sarcoma, which represents a diagnostic imaging challenge. This study aimed to analyze the clinical and ultrasound features of primary and recurrent DFSP to improve the diagnosis.

METHODS

Clinical, imaging, and pathological data from a total of 58 patients (23 patients with primary DFSP and 35 patients with recurrent DFSP) were retrospectively reviewed.

RESULTS

There was no statistically significant difference in age, sex, tumor size, or echogenicity between the two groups. Most of the primary DFSP lesions involved the overlying dermis and hypodermis, while most of the recurrent DFSP lesions were fixated to more deeply seated structures at the original surgical incision. Red nodules on the skin were found more frequently in the primary group. There were statistically significant differences in the type of lesion and ultrasound tumor morphology (p < 0.050). The lesions in the primary group showed more tentacle-like projections or a "claw" sign, while the lesions in the recurrent group were more commonly oval, lobulated, and irregularly shaped. Hypervascularity was common in both groups.

CONCLUSIONS

For primary DFSP, a slow-growing, red nodule on the skin involving the overlying dermis and hypodermis, more frequently a hypoechoic mass with tentacle-like projections or a "claw" sign, was observed. For recurrent DFSP, palpable subcutaneous nodules or subcutaneous masses at the original surgical incision and oval, lobulated, and irregularly shaped lesions were more commonly observed. This may be useful for improving diagnostic accuracy.

Imaging of Pediatric Soft Tissue Tumors and Tumor-like Conditions

Lumps and bumps are frequently seen in children, and the vast majority are a result of trauma, infection, or inflammation. True soft tissue neoplastic lesions are rare; however, their wide and complex classifications make these lesions challenging to manage. Imaging features are usually nonspecific, and a reasonable list of differential diagnoses can be generated following consideration of the clinical presentation, age, and anatomical location of the lesion. In this article, we offer a practical approach to diagnosing such lesions by discussing the most common three benign and malignant lesions in different anatomical regions stratified by age with emphasis on certain features that might aid in the diagnosis such as depth, multiplicity, calcification, or other specific imaging feature.

Can ultrasound distinguish between dermatofibroma and subcutaneous epidermal tumors? - Imaging features and reproducibility

BACKGROUND

We evaluated ultrasound (US) features of dermatofibroma and epidermal tumor (ET). We also evaluated the reproducibility of each US findings.

MATERIALS AND METHODS

We retrospectively assessed US findings of 30 surgically confirmed dermatofibromas and 44 ETs, measuring the lesion (i.e., the depth and the length of the lesion) and calculating the depth to length ratio (DLR). We then determined the sharpness and the shape of the lesion. Finally, we assessed whether the lesion appeared with a "more-than-half sign" (involving more than 50% of the dermal layer) or a "submarine sign" (focal projection to skin). We used Pearson's chi-squared test to analyze the US findings (i.e., presence of more-than-half sign or submarine sign and margin sharpness) between dermatofibroma and ET. Inter-observer agreement of the image findings was assessed using kappa statistics.

RESULTS

The submarine sign and margin sharpness of ET lesions and the more-than-half sign and submarine sign in dermatofibroma, respectively, showed almost perfect agreement. Also, the more-than-half sign and shape of the lesion in ET and the margin sharpness and shape of the lesion in dermatofibroma showed substantial agreement. The measurements of DLRs showed excellent reproducibility. There were no significant differences of DLRs between two groups (p values = 0.512, 0.671, respectively). The more-than-half sign was observed more frequently in the context of dermatofibroma to a statistically significant degree (p < 0.001), while the submarine sign was statistically more common in relation to ET together with greater margin sharpness (p = 0.021 and <0.001, respectively).

CONCLUSIONS

More-than-half signs are common in dermatofibroma while submarine sign and sharp margin are common in ET. Each finding showed high reproducibility and can be useful as a sonographic marker for differentiation between ET and dermatofibroma.

Perineural Invasion as a Clue to Malignant Behavior in a Dermatofibroma

Dermatofibroma (DF) represents one of the most common mesenchymal proliferations of the skin. Their recurrence rate, even when incompletely excised, is very low, whereas the atypical, aneurysmal, and cellular variants have recurrence rates of up to 20% each. Extraordinary rare malignant lesions with metastases to lymph nodes and/or lung have been described. We report a 64-year-old woman with a long history (years) of a skin lesion on her right arm that became painful during the last months. Histologically, it consisted of a conventional cellular DF in which perineural invasion was present. Subsequently, the lesion showed a clinically aggressive course with recurrences, sarcomatous transformation, and pulmonary metastases. Given that no predictive morphological features have been identified to separate classical benign DF from rare metastasizing forms, perineural invasion in an otherwise conventional DF could be a histopathologic clue for an adverse prognosis and should provoke a closer clinical follow-up.