Desmoplastic/Spindle Cell Squamous Cell Carcinoma of the Skin. A Diagnostically Challenging Tumor Mimicking a Scar: Clinicopathologic and Immunohistochemical Study of 6 CasesVelazquez, Elsa F MD; Werchniack, Andrew E MD; Granter, Scott R MDThe American Journal of Dermatopathology: June 2010 - Volume 32 - Issue 4 - p 333-339 doi: 10.1097/DAD.0b013e3181c1d428 Original Study Abstract Author Information Desmoplastic cutaneous squamous cell carcinomas (SCCs) are rare neoplasms with an increased risk of local recurrence and metastasis usually affecting sun-exposed skin of the elderly. Microscopically, they are characterized by elongated cords of atypical epithelial cells associated with a prominent (usually reactive) desmoplastic stroma. To expand this clinicopathologic spectrum, we report 6 cases of an unusual variant of desmoplastic SCC in which the “desmoplastic” areas are predominantly composed of cytologically bland malignant spindle cells mimicking a reactive/benign scarring process. Five patients were males and a patient was a female. The median age at presentation was 72 years. Three patients had history of several years of immunosuppressive therapy for solid organ transplant. All tumors affected sun-damaged skin of the head and commonly infiltrated into the subcutaneous fat and deeper structures. Histopathologically, they were predominantly composed of relatively bland spindle cells in a fascicular pattern. Mitoses ranged from 2 to 4 per 10 high power fields. Pleomorphism was focally seen in all cases. Squamous differentiation in the invasive component was focally seen in 4 cases. SCC in situ was seen in all cases. All cases showed reactivity for keratin immunostains. Median follow-up was 19 months. Two of 6 patients died of metastatic SCC; 1 patient died of unrelated causes; and 3 patients were alive without evidence of disease. Accurate recognition of this entity is essential because of potential misdiagnosis as a benign process including scar and dermatofibroma. Careful search for atypical features and squamous differentiation, immunohistochemical studies, and, in some cases, deeper sections are required to establish the diagnosis. From the Departments of *Pathology; and †Dermatology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA. Reprints: Elsa F. Velazquez, MD, Department of Pathology, Brigham and Women's Hospital, 75 Francis Street, Amory 3, Boston, MA 02115 (e-mail: email@example.com). Copyright © 2010 Wolters Kluwer Health, Inc. All rights reserved.