Photo Quiz

Enlarging Leg Nodule


Am Fam Physician. 2020 Oct 1;102(7):439-440.

A healthy 69-year-old patient presented with an enlarging, nonpainful, nonpruritic nodule just below his right knee that appeared eight months earlier. Twelve years earlier he sustained trauma at the site from a twig, with resulting local atrophy.

Physical examination showed a 3-cm, firm, mobile, nontender, nonpulsatile nodule (Figure 1) on the right lower leg, inferomedial to the popliteal fossa. The lesion had no appreciable punctum or comedone, and there was no surrounding warmth or erythema.




Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

A. Atypical fibroxanthoma.

B. Benign fibrous histiocytoma.

C. Dermatofibrosarcoma protuberans.

D. Merkel cell carcinoma.

E. Pyogenic granuloma.


The answer is C: dermatofibrosarcoma protuberans, a rare malignant soft tissue sarcoma with high rates of local recurrence. It is most often localized to the trunk (50%), proximal extremities (35%), and head and neck (15%).1 Dermatofibrosarcoma protuberans appears as a firm, nodular, or plaque-like fixated lesion of varying color, with occasional discoloration of the surrounding skin. The growth may take months or years to form, resulting in large protuberant nodules. A notable exception is dermatofibrosarcoma protuberans of the scalp, which is associated with early periosteal involvement.2

Presence of the typical

Address correspondence to Samantha J. Bartling, DO, at Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. Dimitropoulos VA. Dermatofibrosarcoma protuberans. Dermatol Ther. 2008;21(6):428–432....

2. Rockley PF, Robinson JK, Magid M, et al. Dermatofibrosarcoma protuberans of the scalp: a series of cases. J Am Acad Dermatol. 1989;21(2 pt 1):278–283.

3. Rutgers EJ, Kroon BB, Albus-Lutter CE, et al. Dermatofibrosarcoma protuberans: treatment and prognosis. Eur J Surg Oncol. 1992;18(3):241–248.

4. Lowe GC, Onajin O, Baum CL, et al. A comparison of Mohs micrographic surgery and wide local excision for treatment of dermatofibrosarcoma protuberans with long-term follow-up: the Mayo Clinic experience. Dermatol Surg. 2017;43(1):98–106.

5. William DJ, Berger TG, Elston DM, et al. Andrews' Diseases of the Skin: Clinical Dermatology. Saunders Elsevier; 2006.

This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

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