Mohs Micrographic Surgery of Primary Cutaneous Mucinous Carcinoma Using Immunohistochemistry for Margin Control DIEGO E. MARRA, MD, n CARL F. S CHANBACHER, MD, n AND A BEL T ORRES , MD nw n Department of Dermatology, Brigham and Women’s Hospital, Harvard Medical School, and Mohs Surgery Center, Dana Farber Cancer Institute, Boston, Massachusetts; and w Department of Dermatology, Loma Linda University Medical Center, Loma Linda, California BACKGROUND. Primary cutaneous mucinous carcinoma is a rare adnexal malignancy with a high recurrence rate following conventional excision and the potential for aggressive local invasion. OBJECTIVE. To enhance the microscopic detection of mucinous carcinoma in Mohs micrographic surgical sections by incorpor- ating rapid immunohistochemical staining. METHODS. Standard Mohs micrographic surgical technique was used in conjunction with frozen section immunohistochemistry using an antibody to low-molecular-weight cytokeratin. RESULTS. Rapid immunoperoxidase staining using low-molecu- lar-weight cytokeratin detected residual foci of mucinous carcinoma that were difficult to identify on routine frozen sections. Immunostaining was strongly positive in areas with clear evidence of tumor by routine histology, as well as in adjacent areas on a subsequent stage where frozen sections were equivocal or negative. Immunostaining was distinctly negative at the final surgical margin, which was shown by en face permanent sections to be free of tumor. The patient has been free of recurrence for 3 years. CONCLUSION. Immunoperoxidase-guided Mohs micrographic surgery using low-molecular-weight cytokeratin enhances the sensitivity for detection of mucinous carcinoma, and may help contribute to complete tumor removal. DIEGO E. MARRA, MD, CARL F. SCHANBACHER, MD, AND ABELTORRES, MD HAVE INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS. PRIMARY CUTANEOUS mucinous carcinoma is a rare epithelial neoplasm histologically related to the eccrine secretory coil. 1,2 It typically occurs on the face and scalp, the eyelid being the most common location. 1 Since its original description by Lennox et al. in 1952, 3 approximately 120 cases have been reported in the literature. Although the tumor gen- erally carries a favorable prognosis, the local recur- rence rate for mucinous carcinoma following traditional surgical excision has been reported to be as high as 43%. 4 Mohs micrographic surgery has been reported in the treatment of mucinous carcinoma, with encouraging results. 5–9 We present a case of mucinous carcinoma treated with Mohs micrographic surgery using im- munohistochemistry for margin control. This techni- que allowed for the identification of tumor not otherwise seen on routinely stained frozen sections, increasing the sensitivity of the procedure and aiding in complete removal of tumor. Case Report A 64-year-old Caucasian woman presented to her primary care physician with an asymptomatic growth on the left inferior-lateral canthus of 1 year’s duration. The lesion was initially clinically diagnosed as a cyst and partially excised. Over a 1-year period the lesion recurred and underwent rapid growth. The lesion was reexcised, revealing histologic evidence of mucinous carcinoma. The patient was referred for Mohs micro- graphic surgery. Skin examination at the time of initial consultation revealed a 0.50.5-cm flesh-colored, ill-defined papule overlying a prior excisional scar on the left inferior- lateral canthus (Figure 1). The regional lymph nodes were not palpable. Investigation for a primary internal malignancy including a complete history and physical examination, chest radiography, mammography, gas- trointestinal endoscopy, and head and neck magnetic resonance imaging was unrevealing. At the time of Mohs micrographic surgery, mucinous carcinoma was easily identified on toluidine blue-stai- ned sections through the main tumor mass, appearing as clusters of basaloid cells with a cribriform pattern surrounded by clear pools of loosely woven mucinous stroma (Figure 2A). Rapid immunostaining of frozen r 2004 by the American Society for Dermatologic Surgery, Inc.  Published by Blackwell Publishing, Inc. ISSN: 1076-0512/04/$15.00/0  Dermatol Surg 2004;30:799–802 Address correspondence and reprint requests to: Carl F. Schanbacher, MD, Mohs Surgery Center, Dana Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, or e-mail: Carl_Schanbacher@dfci.harvard. edu.