Fibrosarcomatous dermatofibrosarcoma protuberans: an unusual tumor in the facial skin.

Sir,

Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive, rarely metastatic, low-grade fibrohistiocytic tumor of the dermis. It is commonly known to occur in the trunk and extremities, less commonly seen in the head and neck region, and its occurrence in the facial skin is perhaps extremely rare. Approximately 85-90% of all DFSPs represent low-grade tumors; the remaining 10-15% contains a component of fibrosarcoma (FS). A transformation of DFSP to FS-DFSP is believed to represent some form of dedifferentiation with an aggressive biological behavior.[12]

A 54-year-old gentleman presented to us with a recurrent swelling in his left cheek, following an attempted excision biopsy at another center 3 months prior, and the slides and blocks review was suggestive of a fibrohistiocytic tumor. Clinical evaluation revealed a residual fairly well circumscribed, firm 3 × 2 cm swelling, 3 cm lateral to the left oral commissure, overlying the left buccinator muscle. The tumor was tethered to the overlying skin along the biopsy scar, the underlying intraoral mucosa was, however, free. There was no significant cervical lymphadenopathy. A CT scan of the head, neck, and chest confirmed the presence and extent of the tumor [Figure 1]. The patient was taken up for surgery and a wide excision of the tumor with the overlying scar was done, and the resultant defect was bridged by a local advancement flap [Figure 2a and b]. The final histopathology was suggestive of a FS-DFSP [Figure 3a–d] with free margins of 1.5 cm all around. He was advised adjuvant radiotherapy in view of the sarcomatous transformation and a concern about the adequacy of the margins. He received 60 grey of external beam radiotherapy and is disease free for the past 1 year [Figure 4a and b].

Figure 1

Axial computed tomography scan of the head and neck showing the tumor in the left cheek

Figure 2

(a) Clinical photograph in the immediate postoperative period and (b) Postoperative specimen photograph

Figure 3

(a) H and E, ×40: Dermatofibrosarcoma protuberans showing storiform pattern of arrangement of fusiform cells, (b) IHC, ×100: Tumor cells showing imunopositivity to vimentin, (c) IHC, ×100: Tumor cells showing imunopositivity to CD34, and (d) IHC, ×100: Tumor cells showing nuclear positivity to Ki-67

Figure 4

(a) Clinical photograph 2 weeks following surgery and (b) Clinical photograph following adjuvant radiotherapy

DFSP accounts for less than 0.1% of all malignant neoplasm's, about 1% of all head and neck malignant tumors, and 7% of all head and neck sarcomas.[3] The clinical appearance of this tumor can be similar to a keloid, an indurated plaque or a nodule; it is hence often mistaken for common benign lesions arising from the skin, and therefore, a tissue diagnosis is imperative. The exact origin of DFSP remains a matter of controversy. A characteristic histology storiform pattern of fusiform cells with infiltration of the dermis and surrounding fat is highly suggestive of the diagnosis. Immunohistochemical markers particularly CD34 has been shown to be useful in aiding in the accurate diagnosis of DFSP as seen in our patient. The other immunostains used for the distinction between dermatofibroma and DFSP in difficult cases are CD 10, Apo D, Factor XIIIA, tenascin, and stromelysin-3.[4]

Wide excision or Mohs micrographic surgery of head and neck DFSP with negative histological margins is the cornerstone of management, and it impacts favorably on local recurrence-free survival.[56] A unique feature of this tumor is the tentacle-like projections of neoplastic cells beneath clinically normal-appearing skin, a factor that has been implicated in the high recurrence rates after standard wide local excision, ranging from 0% to 60% among various studies. Recurrences have been found to be more common in the head and neck region, which may be attributable to delayed patient presentation or a reluctance for wide excision in that region.

Adjuvant radiation has been used to achieve local control when resection margins are microscopically positive or when wide excision would result in severe functional or esthetic impairment for the patient. Recent advances in basic research in DFSP have shown specific chromosomal translocations, arising from a fusion of chromosome regions 17q22 and 22q13, leading to formation of the COL1A1-PDGFB fusion gene, thereby resulting in an overexpression of platelet-derived growth factors (PDGF) beta. This knowledge has resulted in the implementation of targeted therapy with imatinib mesylate, a tyrosine kinase inhibitor, in the management of inoperable and/or metastatic and/or recurrent cases of DFSP.[78]

The challenge in the management of DFSP of the head and neck is in having a high index of suspicion to ensure a prompt early diagnosis apart from the esthetic challenges of performing an excision with histologically negative margins.