The patient
A 65-year-old Caucasian man presented to our clinic with a 10-year history of a slow-growing, painful nodular lesion on the right thigh that was sensitive to cold. The physical examination revealed a well-defined, smooth, purple nodule, 7 mm in diameter, with a peripheral brown rim (Figure 1). The lesion was tender to light touch. Dermoscopy disclosed a multicolored structureless pattern: a purple center surrounded by a whitish area and an outer brown pigmentation (Figure 2). An excisional biopsy of the lesion was performed. Further histopathological examination revealed intradermal sheets of monomorphic round cells, interrupted by enlarged vessels with varying size (Figure 3, hematoxylin-eosin, ×40). A fibrous pseudocapsule surrounding sheets of cells with an eosinophilic cytoplasm and central nuclei was also seen (Figure 4, hematoxylin-eosin, ×100). Immunohistochemically, tumor cells were reactive for smooth muscle actin (Figure 5).
Figure 1.
A well-defined, smooth, purple nodule, 7 mm in diameter, with a peripheral brown rim. [Copyright: ©2015 Oliveira et al.]
Figure 2.
Dermoscopy: a multicolored structureless pattern, a purple center surrounded by a whitish area and an outer brown pigmentation. [Copyright: ©2015 Oliveira et al.]
Figure 3.
Histopathological examination revealed intradermal sheets of monomorphic round cells, interrupted by enlarged vessels with varying size. [Copyright: ©2015 Oliveira et al.]
Figure 4.
Histopathological examination revealed a fibrous pseudocapsule surrounding sheets of cells with an eosinophilic cytoplasm and central nuclei. [Copyright: ©2015 Oliveira et al.]
Figure 5.
Tumor cells were reactive for smooth muscle actin. [Copyright: ©2015 Oliveira et al.]
What is your diagnosis?
Please send your answer to dpc@derm101.com. The first correct answer will receive a DL3N hand dermoscope [cordially sponsored by 3GEN]. The case and the answer to the question will be presented in the next issue of Dermatology Practical & Conceptual.