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June 2009

A Violaceous Nodule on the Knee—Diagnosis

Author Affiliations




Arch Dermatol. 2009;145(6):715-720. doi:10.1001/archdermatol.2009.111-b

Hematoxylin-eosin staining of the punch biopsy specimen revealed a neoplasm in the dermis that was composed of small blue cells (Figure 2). The cells were arranged as solid nests with a trabecular growth pattern at the periphery. High-power examination revealed uniform tumor cells with round to oval nuclei and scant cytoplasm (Figure 3). The tumor cells had distinct nuclear membranes, finely distributed chromatin, and inconspicuous nucleoli. Mitotic figures were abundant. The cells stained positive for neuron-specific enolase and cytokeratin 20, with a characteristic perinuclear dot pattern (Figure 4). Further investigation, which included blood work, radiography of the chest, and computed tomography of the abdomen, showed no abnormalites and was negative for metastatic spread. A wide local excision was performed, followed by a sentinel lymph node biopsy (SLNB). The SLNB showed tumor invasion in 1 sentinel node, and the patient subsequently underwent an elective lymph node dissection. After she discussed the risks and benefits of adjuvant radiation therapy and/or chemotherapy with the oncologist, she decided against pursuing additional therapies and is currently undergoing close clinical follow-up.

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