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Sialadenoma papilliferum of the hard palate: report of 2 cases and immunohistochemical evaluation. (Case Report).

* This study reports on the clinical and histologic features of 2 previously unreported cases of sialadenoma papilliferum. Immunohistochemical analysis of one of the cases demonstrated that the ductal cell component shows both epithelial and myoepithelial differentiation. (Arch Pathol Lab Med. 2001;125:1595-1597)


Abrams and Finck (1) first used the term sialadenoma papilliferum in 1969 to describe 2 cases of an unusual neoplastic salivary gland proliferation. Slightly more than 50 cases have been reported in the English-language literature. (2) Grossly, the neoplasm is a well-circumscribed, round-to-oval excrescence of the mucosal surface. Histologically, it shows branching ductal structures that extend into the papillary mucosa above the level of the adjacent mucosa. This ductal proliferation shows abrupt transition into stratified squamous epithelium that covers the mucosal papillae. The histogenesis of sialadenoma papilliferum is still unclear. Some authors have suggested pluripotential myoepithelial cells as precursors of sialadenoma papilliferum and basal pluripotential cells. Since squamous differentiation is present, excretory ducts have also been implicated as the site of origin. (1,3-5) In the present study, we describe 2 additional cases and analyze the immunohistochemical staining pattern of 1 of the cases.


Case 1

A 72-year-old man was referred for evaluation of sore throat and a slowly enlarging palate lesion. A 4-mm exophytic growth on the hard palate was identified. The patient underwent an excision of the lesion, and reconstruction with a soft palate flap was performed. Follow-up showed no evidence of recurrence at 3 months.

Case 2

A 58-year-old man presented with a 5-mm hard palate lesion that was somewhat pigmented, and the clinical differential diagnosis included melanoma. The lesion was excised, and because the initial margins of resection were involved, a conservative reexcision was performed. No recurrence has been noted.


Grossly, the excised mass from case I was 0.6 cm in diameter with an overall smooth surface, except for several verrucous structures in the center of the specimen. Histologically, the lesion showed an exophytic papillary proliferation composed of well-differentiated stratified squamous epithelium, which merged with a glandular proliferation occupying the submucosa. The stratified squamous epithelium in the exophytic portion was hyperplastic with hyperkeratosis, parakeratosis, and focal hypergranulosis. The squamous epithelium also showed acute inflammation and spongiosis. The ductal structures showed an irregular outline with infoldings of the glands. The ductal epithelium was composed of luminal columnar cells with abundant cytoplasm and basally located round nuclei. Scattered cells showed vacuolization and mucin production. There was also a discontinuous layer of basally located cells in the ductlike structures composed of cuboidal to spindle-shaped cells.

The tumor in case 2 measured 0.5 cm. Histologically, the tumor was similar to that seen in case 1, except that much of the surface papillary projections were ulcerated to the level of the surrounding mucosa. Nevertheless, characteristic ductal proliferation was present, and laterally there were characteristic papillary structures that merged into the ductal areas. An inflammatory reaction, stromal edema, and poor circumscription gave an invasive appearance to the ductal portions.

Only case 1 was available for immunohistochemical evaluation. Antigen unmasking with citrate buffer, pH 6.0, was performed for CD1a, vimentin, desmin, and cytokeratin (CK) 7. Pretreatment with proteinase K, 25 [micro]g/mL, was performed for the low-molecular-weight keratin CAM 5.2 and CK20. Trypsin, 1 mg/mL, pretreatment was performed for AE1/3. The remaining antibodies required no pretreatment. CD1a, vimentin, desmin, CAM 5.2, CK7, and CK20 (Dako Corporation, Carpinteria, Calif) were detected with the Dako LSAB Plus Kit. Muscle-specific actin (MSA), smooth muscle actin (SMSA), S100, carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), and polyclonal and monoclonal glial fibrillary acidic protein (GFAP) (all from Dako) were detected with the Dako LSAB II kit. The keratin cocktail AE1/3 (Vector, Burlingame, Calif) was detected with the Vector Elite ABC Kit.

Immunohistochemical stains of the squamous papillae demonstrated homogenous positivity for CK7, AE1/3, CEA, and EMA. Immunohistochemical stains revealed the luminal columnar cells of the ductal structures to express CK7, CAM 5.2, AE1/3, CEA, and EMA (Figure). The stains also highlighted basally located (abluminal) cuboidal to spindle-shaped cells in the ductal structures with strong CK7 and vimentin staining. The CK7 was somewhat weaker than in the luminal cells. Focal SMSA positivity was seen in the abluminal ductal structures but was not as strong as in the surrounding normal submucosal glands. Anti-S100 protein antibodies revealed staining of both the luminal and basally located cells. CD1a staining revealed scattered dendritic cells in the squamous but not the glandular epithelium. There was only a slight increase in CD1a-positive cells in the squamous epithelium of the neoplasm when compared with the surrounding normal epithelium. No staining for GFAP, desmin, CK20, or MSA was seen in any portion of the neoplasm, whether of squamous or ductal differentiation.



Sialadenoma papilliferum is a rare benign tumor of salivary gland origin and was described as sialadenoma papilliferum in 1969. (1) Rare cases have been reported in major salivary glands, including 1 of the first 2 cases described by Abrams and Finck. (1) The features of the 2 current cases are similar to previous observations. Both cases occurred in the hard palate in men older than 40 years. Case 1 had a central papilloma-like appearance. Case 2 was clinically thought to be possibly melanoma because much of the surface papillomatous growth had eroded, and it is likely that the ulcerated and dark appearance gave a false clinical impression of melanoma. Careful examination of the tumor revealed a small solid-to-cystic mass underlying the partially ulcerated surface.

The biphasic appearance of sialadenoma papilliferum is characteristic and could be a useful clinical finding. The gross appearance of the tumor is explained by the microscopic finding of collections of ductlike spaces underlying a verrucous-like proliferation of squamous epithelium. The ductlike structures were composed of tall columnar cells, and although they were the major cell type lining these ductlike spaces, goblet cells were also identified. Even though one of our cases demonstrated superficial ulceration of some of the papillary squamous structures, the underlying ductal structures remained intact. Lateral portions of the lesion exhibited the typical papillary squamous proliferation.

Abrams and Finck (1) first postulated the presence of myoepithelial cells as one of the components of ductal structures in sialadenoma papilliferum. More recent studies have described the immunohistochemical findings in some of these unusual tumors. Nakahata et al (6) described the ductal cells as expressing CK1, vimentin, and desmin. Maiorano et al (7) reported 5 new cases of sialadenoma papilliferum and the immunohistochemical reactivities of these cases. These authors described both adluminal and basally located cells. The adluminal cells of the ductlike structures reacted with CK19 and S100. Two subsets of basally located cells were identified with immunohistochemistry. One cell subset expressed CK14, S100, GFAP, vimentin, and SMSA. The second group expressed CK13 and CK14 but not the other antibodies studied. In the present study, immunohistochemical analysis showed basally located ductal cells demonstrating CK7, vimentin, S100, and focal SMSA immunoreactivity. The morphologic and immunohistochemical features of this cell subset of sialadenoma papilliferum strongly suggest its myoepithelial differentiation. Mairono et al (7) described CD1a cells in their cases as did we. The significance of finding Langerhans cells in this tumor is unclear. They did not appear to be significantly increased in the tumor epithelium when compared with the surrounding epithelium.

We believe the immunohistochemical stains in our case point to myoepithelial cell participation of this neoplasm, similar to what has been previously demonstrated by Maiorano et al. (7) However, the tumor's biphasic appearance with distinct ductal and squamous elements suggests that the tumor also mirrors what might be expected of a tumor with differentiation toward that of an excretory duct. Most importantly, the tumor is recognized as benign with only rare recurrence. (8,9) Mucosal tumors of salivary gland origin are not infrequently malignant, and the appearance of the ductal structures can simulate invasion as was seen in one of our cases. Recognition of the components of this tumor should help in the correct classification of this lesion.


(1.) Abrams AM, Finck FM. Sialandenoma papilliferum: a previously unreported salivary gland tumor. Cancer. 1969;24:1057-1063.

(2.) Argyres MI, Golitz LE. Sialadenoma papilliferum of the palate: case report and literature review. J Cutan Pathol. 1999;26:259-262.

(3.) Freedman PD, Lumerman H. Sialadenoma papilliferum. Oral Surg. 1978; 45:88-94.

(4.) Nasu M, Takagi M, Ishikawa G. Sialadenoma papilliferum: report of case. J Oral Surg. 1981;39:367-369.

(5.) Mitre BK. Sialadenoma papillifurem: report of case and review of literature. J Oral Maxillofac Surg. 1986;44:460-474.

(6.) Nakahata A, Deguchi H, Yanagawa T, Yoshida H, Sato M, Hayashi Y. Coexpression of intermediate-sized filaments in sialadenoma papilliferum and other salivary gland neoplasms. J Oral Pathol Med. 1990;19:313-318.

(7.) Maiorano E, Favia G, Ricco R. Sialadenoma papilliferum: an immunohistochemical study of five cases. J Oral Pathol Med. 1996;25:336-342.

(8.) Pimentel MTY, Amado ML, Sarandeses AG. Recurrent sialadenoma papilliferum of the buccal mucosa. J Laryngol Otol. 1995;109:787-790.

(9.) Rennie JS, Macdonald DG, Critchlow HA. Sialadenoma papilliferum: a case report and review of the literature. Int J Oral Surg. 1984;13:452-454.

Accepted for publication June 1, 2001.

From the Departments of Pathology, University of Iowa Hospitals and Clinics (Drs Ubaidat and Robinson), and Mercy Hospital (Drs Belding and Merryman), Iowa City, Iowa.

Reprints: Robert A. Robinson, MD, PhD, Department of Pathology, University of Iowa Hospitals and Clinics, 200 Hawkins Dr, Iowa City, IA 52242 (e-mail:
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Author:Ubaidat, Manaf A.; Robinson, Robert A.; Belding, Paul J.; Merryman, Don J.
Publication:Archives of Pathology & Laboratory Medicine
Geographic Code:1USA
Date:Dec 1, 2001
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