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Eccrine syringomatous carcinoma (ESC) is a rare malignant adnexal skin tumor derived from sweat glands1 that occurs in middle-aged patients. Clinically, ESC is usually seen as a slow-growing, solitary, flesh-colored nodule or plaque with ill-defined margins.1 Because ESCs tend to infiltrate far beyond the visible margins of the lesion, surgical excision under Mohs microscopic control must be performed.
Ex vivo fluorescence confocal microscopy (FCM) has been introduced as a novel imaging technique that permits quick and complete imaging of the tumor margins on fresh tissue excisions from Mohs surgery.2- 5 In this case series, we aimed to report the application of FCM for ESC diagnosis and margin assessment.
A man in his 60s sought consultation for the presence of a growing, solitary, flesh-colored patch located on his scalp with shading of margins. Dermoscopically, the lesion revealed a vascular pattern with blurred arborizing vessels overlying a whitish background. A provisional diagnosis of epithelial tumor was made, and Mohs surgery using FCM was scheduled. Fresh excised tissue was processed for FCM as described elsewhere.2- 5 After FCM imaging, the specimen was processed for conventional frozen-section and definitive histopathologic examination.
On FCM, the tumor appeared as a dermal proliferation of highly fluorescent cells. The overlying epidermis was spared by any neoplastic proliferation and not ulcerated. At higher magnification, the tumor was made up of neoplastic cords of monomorphous fluorescent cells similar to eccrine gland tubular structures. All margins were clear at first staging. Histopathologic examination confirmed the diagnosis of an ESC.
A woman in her 50s was referred for the presence of a long-standing whitish patch located on the right side of her nose (Figure, A). Dermoscopically, pinkish arborizing vessels were observed (Figure, B). Since the margins were clinically indistinct, Mohs surgery with FCM was performed. Central section of the tumor revealed the same pattern observed in case 1, and the diagnosis of ESC was made on FCM images.
A, Whitish patch located on the nose of a 53-year-old woman (arrowhead) (measuring scale graded in centimeters). B, Dermoscopically, the tumor was typified by the presence of pinkish arborizing vessels (arrowhead). C, An FCM mosaic of 1 margin (first staging) depicts the presence of a dermal proliferation of highly fluorescent structures (scale bar represents 700 μm) that correspond to the presence of neoplastic eccrine-like cords (D) (arrowheads; scale bar represents 100 μm). E, At second staging of Mohs surgery, the FCM mosaic revealed a clear margin (scale bar represents 700 μm). F, High-resolution FCM image (scale bar represents 100 μm) shows the presence of inflammatory cells without any neoplastic proliferation (arrowheads).
Interestingly, 1 margin was found to be positive for the presence of tumor cells (Figure, C and D); thus, a second staging was performed to obtain a clear margin (Figure, E and F). Histopathologic examination confirmed the complete excision and the diagnosis of ESC with an excellent correlation with the FCM analysis.
Fluorescence confocal microscopy is a novel technique that can speed up Mohs surgery procedures in the context of epithelial tumors. It allows imaging of large areas of tissue with a high resolution, similar to that seen in histopathologic samples.3,4 Herein, we report 2 cases of ESC, a rare malignant adnexal tumor, in which FCM allowed rapid assessment of the clearance of the margins during Mohs sessions.
As a first step, on FCM images it was possible to understand the epithelial origin of the tumor because of the presence of fluorescent tumoral structures forming cords or single cells located in the mid-dermis. Of note, the neoplastic proliferations did not show any peripheral palisading. Although an exact diagnosis of ESC was not possible in case 1 owing to the rarity of the tumor and thus the relatively scarce experience of the FCM reader, the lesion was provisionally identified as an epithelial tumor. Interestingly, case 2 was correctly diagnosed as ESC on FCM. As a second step, the clearance of the margins was easily assessed on FCM.
Our experience with FCM in ESC suggests the possibility of its application in several settings. Moreover, we provide the morphologic description of FCM findings in ESC that can help to build up a complete semiology for this new intriguing technique.
Corresponding Author: Caterina Longo, MD, PhD, Skin Cancer Unit, Arcispedale Santa Maria Nuova IRCCS, Viale Risorgimento, 80, 42100 Reggio Emilia, Italy (firstname.lastname@example.org).
Published Online: May 27, 2015. doi:10.1001/jamadermatol.2015.1008.
Conflict of Interest Disclosures: None reported.
Longo C, Ragazzi M, Gardini S, Moscarella E, Argenziano G. Ex Vivo Fluorescence Confocal Microscopy of Eccrine Syringomatous CarcinomaA Report of 2 Cases. JAMA Dermatol. 2015;151(9):1034-1036. doi:10.1001/jamadermatol.2015.1008