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Case Reports

Abstract

Plasmacytoid squamous cell carcinoma (SCC) is a rare variant, which, to the best of our knowledge, has been previously reported only once on the vulva and once on the skin of the shoulder. These cases showed an aggressive clinical course, highlighting the importance of prompt diagnosis and treatment [1][2]. We present an additional case of cutaneous plasmacytoid SCC in a 73-year-old woman who presented with a 2-month history of a spontaneously bleeding left temple lesion. Her history was significant for CD20-negative B-cell acute lymphoblastic leukemia, actively undergoing immunotherapy. Shave biopsy showed a superficial dermal infiltrate of dyscohesive oval-to-round cells with eccentric nuclei and a perinuclear hof, suggestive of plasma cells. By immunohistochemistry, the cells were strongly positive for CK5/6, 34betaE12, CD138, and p63, with patchy positivity for p40, and were negative for MUM1, CD34, desmin, CK7, CK20, Melan-A, SOX10, and mucicarmine. A diagnosis of plasmacytoid SCC was made. CT of the head and neck showed no signs of metastatic disease. The patient underwent Mohs micrographic surgery, and the tumor was cleared in a single stage with local advancement flap closure. The debulk specimen was sent for permanent pathology and showed features consistent with poorly differentiated SCC. Considering the rarity of plasmacytoid SCC arising from the skin, our case provides further data concerning the clinical presentation, behavior, and treatment of this malignancy. CD138 staining must be interpreted with caution in this context, as it stains squamous epithelium as well as plasma cells.