Unusual presentation of dermatofibrosarcoma protuberans in deep skin over the breast - imaging findings.

Abstract

INTRODUCTION Dermatofibrosarcoma protuberans (DFSP) is a rare locally aggressive tumor of the dermis and subcutaneous tissue that commonly appears on upper extremities and on the trunk. There is a slight male predominance and the lesion is commonly seen between the second and fifth decades of life. The tumor grows slowly over years and rarely metastasizes; however, local recurrence is frequent. The most common sites for metastasis are lymph nodes and the lungs. The treatment of the tumor is resection with wide margins (1,2). Here we present radiologic findings of DFSP with unusual presentation located in the deep skin over the breast, which was excised successfully and without local recurrence during a 36-month follow-up period. CASE REPORT A 36-year-old female with a palpable right breast mass located in the upper inner quadrant and change in skin color without a significant history was admitted to surgery department. She claimed that the mass had first appeared two years before and was slowly growing. She had no history of recent trauma or surgical operation. On inspection, a well circumscribed, plaque type lesion was observed, along with a violet-purple change in color of the skin over the right breast (Fig. 1). The patient reported neither systemic disease or known illness nor continuous drug usage. Physical examination was unremarkable except for a well-defined non-tender mass on the right breast. The left breast and bilateral axillaries were normal. The patient was referred for radiologic examination to exclude a primary breast tumor. Bilateral breast ultrasound (US) and color Doppler ultrasound (CDUS) was performed with a Toshiba, Powervision 6000 SSA-370A (Tokyo, Japan) with 6-11 MHz high frequency linear transducer.US demonstrated a 3.5x1.5 cm sized solid, hyperechogenic lesion with sharp margins in the subcutaneous fat tissue, without marked vascularity on CDUS (Fig. 2). The left breast and both axillaries were unremarkable. The right mammography (HFXPlus-Fischer Imaging, Denver, USA) on mediolateral oblique (MLO) projection showed a well-defined bilobulated density with irregular margins and no calcifications (Fig. 3). Based on the mammography and sonography findings, the mass was considered suspect of malignancy and breast magnetic resonance imaging (MRI) study was planned for further examination. A contrast-enhanced breast MRI was performed using a 1.5 tesla MR unit (Somatom Vision Plus, Siemens, Erlangen, Germany) at our institution. Unfortunately, the mass could not be demonstrated on either T1, T2 or postcontrast subtracted images (Fig. 4). The patient was referred to surgery department and wide excision of the mass was performed. On pathologic evaluation, spindle cells were seen to be arranged in a storiform pattern, with minimal pleomorphism (Fig. 5). Immunohistochemical stain with CD34 was positive (Fig. 6) and definitive histologic diagnosis was DFSP. On follow-up, 36 months after surgical treatment, the patient continued to be symptom free, with no signs of tumor recurrence. DISCUSSION Dermatofibrosarcoma protuberans is a rare fibrous tumor of the soft tissue, commonly arising from dermis and subcutaneous tissue, which was first described by Darier and Ferran in 1924 (3). It accounts for 0.1% of all malignant tumors and 1% of all soft tissue sarcomas. The tumor is mostly located on the trunk skin (50%-60%) and is more common in men than women. The majority of these tumors are less than 5 cm in diameter. It can be seen at any age but it is much more common between ages 20 and 50, however, there are few cases reported in early childhood. DFSP has an indolent growth pattern and its symptoms are mostly long lasting, spanning over months and years (1,2,4). DFSP poses a diagnostic challenge as the clinical symptoms and the radiologic signs are nonspecific. The tumor usually causes a red-purple change of color on the overlying skin on inspection, and if it presents with a red and irregular bordered lesion, it can mimic a hemangioma. When DFSP is located in the breast, it can be mistaken for primary breast tumor and the accurate diagnosis is difficult to reach. Usually after clinical evaluation, US is the first choice for imaging and CDUS is very helpful for vascular situation but neither of the modalities is specific for diagnosis. Shin et al. report that a diagnosis of DFSP should be considered if US reveals an oval mass in the subcutaneous tissue that is abutting against the skin and has a focal lobulated margin with hypoechogenicity or an irregular margin with mixed echogenicity (5).Although an echogenic macrolobulated oval mass located over the breast lying in the deep dermis and the subcutaneous tissue without marked vascularization was demonstrated, an exact diagnosis could not be made in the present study. Unfortunately, mammography was also found to be nonspecific, with macrolobulated density on MLO projection. Considering mammography and sonography findings, a primary breast tumor could not be excluded and the present case was classified as BI-RADS category 4. Computed tomography is not indicated unless bony invasion or pulmonary metastasis is suspected in some occasional cases. Although MRI is also nonspecific for the exact diagnosis of DFSP, it is useful for identifying the extent and location of the mass, especially in large recurrent tumors. In addition, the areas of hemorrhage within the tumor may be demonstrated by use of MRI and can suggest the diagnosis (6,7). Another current imaging modality, multivoxel proton [1H]) MR spectroscopy (MRS), is accepted as an adjunctive method to breast MRI on differential diagnosis of benign versus malignant tumors. A recent case study of DSFP located on the breast, reported by Ivanovic et al., did not show significant cholin peak on [1H] MRS (8). In the present case, the mass could not be demonstrated on either T1 or T2 weighted images, and there was no significant enhancement on post-contrast subtracted images on breast MRI examination. It is considered that the discrimination failed both on pre- and post-contrast images as the mass was probably carrying similar signal characteristics of the adjacent subcutaneous fat tissue in which the lesion developed. Complete surgical resection is accepted as the optimal treatment for primary or recurrent DFSP. Studies have shown that resection with wide margins is essential and recurrence rates after local resection are reduced while the excision margins are widened. The combination of adjuvant radiotherapy before or after the surgery is a treatment option, particularly in those who cannot undergo wide surgical excision for several reasons. In addition, there are some successful clinical reports on imatinib, a tyrosine kinase inhibitor, which can induce regression in patients with unresectable or metastatic DFSP (1,2,4). Proper follow-up seems critical since the most significant characteristic of the tumor is recurrence, and local recurrence generally occurs in the first 3 years after surgery. Sonographic evaluation and re-biopsy is advisable if suspicion occurs. In addition, mammography might be helpful in the diagnostic work-up in breast located tumors for periodic control of recurrence. In conclusion, DFSP is a rare soft tissue tumor of cutaneous origin that mostly occurs on the trunk and might be rarely seen on the breast skin and can be confused with primary breast tumors. We believe that the importance of the present case is to upgrade the awareness of this soft tissue tumor while keeping in mind the differential diagnosis of other breast tumors.