[1250] Cutaneous Adenexal Differentiation in Salivary Benign Mixed Tumors

LA Schmidt, SH Olsen, JB McHugh. University of Michigan, Ann Arbor, MI

Background: Cutaneous adenexal differentiation (CAD) is well-recognized in benign mixed tumors occurring in cutaneous sites. The incidence of this histologic finding in salivary gland sites is not known. We sought to describe the incidence of CAD in benign mixed tumors of the palate, lip, and parotid gland.
Design: Benign mixed tumors of the palate (n=29), lip (n=13), and parotid gland (n=37) resected between 1980 and 2009 at a single academic medical institution were reviewed. All hematoxylin and eosin stained sections containing neoplasm were reviewed by all authors which included one dermatopathologist (S.O.). After confirming the diagnosis of mixed tumor, we evaluated for morphologic evidence of CAD and metaplastic stromal changes. Specifically we evaluated for the presence of infundibulocystic structures, tricholemmal keratinization, shadow cells, follicular epithelial differentiation, follicular bulb or papillary mesenchymal body-like structures, and sebaceous differentiation. Chart review was performed to obtain pertinent clinical information.
Results: Cutaneous adenexal differentiation was seen in 17% of palate and 38% of lip benign mixed tumors but in no parotid tumors (Table). The most frequent features were tricholemmal keratinization (38% of lip and 17% of palate tumors), follicular epithelial differentiation (38 and 17%), and infundibulocystic structures (23 and 14%). Sebaceous differentiation was seen in only one palate tumor. Varying amounts of stromal adipose were seen in 62, 34, and 21% of lip, palate and parotid tumors. Osseous metaplasia was seen in one tumor from each site.

Table: Summary of Clinical and Histologic Features

Site	# of cases	# with CAD	% with CAD	Mean age, yrs (range)	M:F	Mean size, cm (range)
Palate	29	5	17	45 (12-81)	16:13	2.3 (0.8-6)
Lip	13	5	38	49 (27-88)	7:6	1.4 (0.4-3)
Parotid	37	0	0	48 (21-84)	11:26	2.5 (0.6-6.5)

Conclusions: Cutaneous adenexal differentiation was identified in a significant number of benign mixed tumors of the lip (38%) and palate (17%) but in no parotid tumors. The most frequent histologic features of this were infundibulocystic structures, tricholemmal keratinization, and follicular epithelial differentiation. When such changes become prominent, it can present a diagnostic pitfall that must not be over interpreted as squamous cell carcinoma at biopsy or frozen section. Our finding of CAD in 38% of benign mixed tumors of the lip reconfirms previous reports of such differentiation in up to 44% of cutaneous benign mixed tumors.
Category: Head & Neck

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 159, Wednesday Morning