History as submitted:  A 35-year-old male presented with an ulcerated protuberant mass on his abdomen (Figures 1 & 2), procrastinated under his impression that it was a "hernia". Excision of the partly necrotic tumor (Figure 3) with a less than one centimeter underlying soft tissue margin was carried out. Histological representation is presented in figures 4 - 6.

Your diagnosis? 

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This is dermatofibrosarcoma protuberans with fibrosarcomatous areas, narrowly excised.

The two-thirds of the mass to the left in CT (Figure 2) and left in the gross photo (Figure 3) had conventional storiform CD34-positive dermatofibrosarcoma protuberans (DFSP) histology (Figures 4 & 5). Fibrosarcomatous histology (Figure 6) constituted the right lateral-most tumor, i.e., the somewhat more radiodense and partly necrotic lobule in Figure 3 that constituted 35% of the mass. Postoperative radiotherapy was elected rather than the complex abdominal wall reconstruction that would have been required to obtain the recommended benign margin. He is two months post-completion of that treatment with no evidence of the disease.

DFSP is a rare fibroblastic skin tumor of the intermediate malignancy, usually presenting as a nodular cutaneous mass on the trunk and proximal extremity of young and middle aged adults. The tumor grows slowly, typically over years. Its pathogenesis has not yet been fully clarified. Recent basic genetic research has shown chromosomal translocations, generally termed "ring chromosomes". These arise from a fusion of chromosome regions 17q22 and 22q13, the gene loci which code the alpha chain of type I collagen (2). This translocation fuses the collagen type l alpha 1 (COL1A1) gene to the platelet-derived growth factor B-chain (PDGFB) gene. This leads to abnormal activation of the platelet-derived growth factor receptor beta tyrosine kinase through an autocrine loop. This is believed to be the critical event in DFSP tumorigenesis. Imatinib mesylate is a potent inhibitor of several protein tyrosine kinases, including the PDGFRs. Clinical evidence suggests that imatinib mesylate is a safe and effective treatment for DFSP, especially in cases of recurrent or metastatic disease. So DFSP is now susceptible to a specific molecular-targeted therapy (4).

The standard treatment for DFSP is wide local excision with at least a three centimeter margin (3, 5). Local regional recurrence is reported in up to as much as 50%, emphasizing the need for wide margins for local control. The extent of this tumor can be estimated by CT and more precisely with MRI (2). Yet even these techniques fail to detect the fine tumor fascicles extending into the adjacent connective tissue and fat. Its locally infiltrative growth pattern can have clinically unapparent extensions that often extend for long distances in a horizontal direction (2).

Of 21 cases, the mean size of the lesions was 5.6 centimeters, mostly located in the trunk. Of the cases, 61.9% underwent surgical excision without previous biopsy (6) and 52.4% of the patients presented positive margins that required surgical extension. The recurrence rate was 28.6% (six cases), five of them were local recurrences that were treated with new surgical excision with wide margins. The median period of being free of illness was 32.5 months. Most recurrences appear within the first three years, but long-term follow-up of these patients is important (6).

Approximately 10-15% of all DFSPs (5) contain areas of fibrosarcoma, and then tend to exhibit more aggressive behavior, and a small fraction of these metastasize. Clinicopathologic features of 18 cases of sarcomas arising in DFSP treated by wide local excision and having follow-up of at least five years were analyzed (7). The tumors involved the trunk (seven), scalp (four), extremities (four) and inguinal region (three) and ranged from 1.5 to 7.0 centimeters (median was 4.0 centimeters). Sarcoma occurred de novo in 15 cases and in a recurrence in three. Sarcomas resembled fibrosarcoma in 17 and pleomorphic undifferentiated sarcoma (a.k.a. malignant fibrous histiocytoma) in one. The sarcomatous areas occupied between 20-80% of the tumor (the median was 60%). All tumors expressed CD34 in the DFSP component but only nine (50%) in the sarcomatous component. In the present case, the fibrosarcomatous area (Figure 6) labeled strongly for CD34. All patients were treated by wide local excision with negative margins; these additionally received radiation. Four patients (22%) developed recurrences, but none developed metastasis during the follow-up period of 62 months to 17 years (the median was 81.5 months). In contrast to earlier studies, this demonstrates that patients with sarcomas arising in DFSP do not have an increased risk of distant metastasis within a five-year follow-up period, provided they are treated by wide local excision with negative margins. This probably reflects the fact that wide local excision results in eradication of local tumor, thereby eliminating the source for subsequent dissemination.

This case illustrates the clinical context added by inquiring after radiologic studies in some dermatology cases.

REFERENCES:

1. Abrams TA, Schuetze SM. Targeted therapy for dermatofibrosarcoma protuberans. Curr Oncol Rep. 2006 Jul;8(4):291-6.

2. Breuninger H, Sebastian G, Garbe C. Dermatofibrosarcoma protuberans--an update. J Dtsch Dermatol Ges. 2004 Aug;2(8):661-7.

3. Chang CK, ET AL. Outcomes of surgery for dermatofibrosarcoma protuberans. Eur J Surg Oncol. 2004 Apr;30(3):341-5.

4. Fiore M, ET AL. Dermatofibrosarcoma protuberans treated at a single institution: a surgical disease with a high cure rate. J Clin Oncol. 2005 Oct 20;23(30):7669-75.

5. Mendenhall WM, Zlotecki RA, Scarborough MT. Dermatofibrosarcoma protuberans. Cancer. 2004 Dec 1;101(11):2503-8.

6. Ruiz-Tovar J, ET AL Dermatofibrosarcoma protuberans: review of 20-years experience. Clin Transl Oncol. 2006 Aug;8(8):606-10.