Basal cell adenocarcinoma of minor salivary glands.
Abstract: Basal cell adenocarcinoma of minor salivary glands is a relatively rare slow-growing tumor with an infiltrating growth pattern. The infiltrating growth pattern and likelihood of vascular and perineural involvement distinguishes basal cell adenocarcinoma from basal cell adenoma. Other diagnostic considerations include adenoid cystic carcinoma and basaloid squamous carcinoma. Basal cell adenocarcinomas show strong immunoreactivity to cytokeratin 7 and variable myoepithelial staining with S100. It is necessary to differentiate basal cell adenocarcinoma from other basaloid cell tumors of the minor salivary glands because of the prognosis and potential differences in treatment, particularly adenoid cystic adenocarcinoma and basaloid squamous carcinoma. Surgical excision with a wide margin to ensure complete removal has been suggested as the primary treatment for basal cell adenocarcinoma. Radiotherapy has been proposed for lesions in the minor salivary glands because of the higher likelihood of vascular and neural invasion and for those that are diffusely infiltrative.
Article Type: Report
Subject: Salivary gland tumors (Risk factors)
Salivary gland tumors (Diagnosis)
Salivary gland tumors (Care and treatment)
Salivary gland tumors (Research)
Authors: Farrell, Tisha
Chang, Yilan L.
Pub Date: 10/01/2007
Publication: Name: Archives of Pathology & Laboratory Medicine Publisher: College of American Pathologists Audience: Academic; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2007 College of American Pathologists ISSN: 1543-2165
Issue: Date: Oct, 2007 Source Volume: 131 Source Issue: 10
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: United States Geographic Code: 1USA United States
Accession Number: 230416931
Full Text: Basal cell adenocarcinoma was introduced in the World Health Organization classification of salivary tumors in 1991. (1) It is classified as a low-grade malignancy in the latest World Health Organization classification (2005). (2,3)

CLINICAL FEATURES

A recent literature review revealed only 21 previously reported cases of basal cell adenocarcinoma of oral minor salivary glands. (3) The histogenesis is still unknown. Although some authors propose it may develop from a pre-existing basal cell adenoma, most, however, believe it is a de novo lesion. (4) Basal cell adenocarcinoma accounts for less than 2% of all salivary gland tumors. More than 90% of cases involve the parotid gland. (3,5) The involvement of the minor salivary glands is very rare, and only several cases have been reported involving the palate, buccal mucosa, labial mucosa, and the submandibular gland. (4) The age of patients with basal cell adenocarcinoma of the minor salivary glands ranges from 24 to 73 years with a mean age of 55.1 years. (3) Each gender is equally affected.

Clinically, basal cell adenocarcinoma of the minor salivary glands presents with asymptomatic swelling of many years duration, often in excess of 10 years. (4) Rarely will cases present with pain and tenderness.

MACROSCOPIC FEATURES

Both basal cell adenoma and basal cell adenocarcinoma have similar features. The cut surface may be tan-white to gray or brown. There may be areas of cyst formation. There may be visible infiltration in adjacent tissues.

MICROSCOPIC FEATURES

Histologically, basal cell adenocarcinoma is composed of 2 cell types: smaller cells with scant cytoplasm and dark nuclei, and polygonal cells with eosinophilic to amphophilic cytoplasm and pale basophilic nuclei (3,6) (Figure 1). The cells are arranged in nests that vary in size and shape with intervening collagenous stroma (Figure 2). The smaller cells often show a palisading arrangement at the periphery of the tumor nests. Four histomorphologic patterns have been described in basal cell adenocarcinoma. The most common architectural pattern is a solid form; the remainder are membranous, tubular, and trabecular forms. (3,6) The distinction between basal cell adenocarcinoma and basal cell adenoma is whether there is the presence of infiltrative growth of tumor cells into adjacent normal structures (Figure 3). True invasion must be distinguished from both multinodularity with a pushing type of growth pattern and multifocal origin in adjacent salivary lobules, both of which are features of basal cell adenoma. (4) Neural and vascular invasion may be present (Figures 4 and 5). Cellular atypia and mitosis may be present and variable and do not warrant the diagnosis of malignancy but may be helpful if there is a lack of surrounding tissue.

ANCILLARY STUDIES

All studied tumors showed diffuse or focal strong positivity for cytokeratin (CK) 7 and demonstrated negative (or, rarely, focal weak) staining for CK20. (3) Positivity for carcinoembryonic antigen and epithelial membrane antigen were noted. The presence of myoepithelial cells was demonstrated by moderate to strong expression of S100. (3) Tumors did not demonstrate expression for glial fibrillary acidic protein or smooth muscle actin. (3) The tumor suppressor gene p53 product was explored in 2 cases, 1 of which demonstrated moderate staining of fewer than 50% of the cells. (3) Also, the oncogenic protein Bcl-2, known to prolong cell survival by inhibiting apoptosis, was strongly positive in 2 reported cases. (3)

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DIFFERENTIAL DIAGNOSIS

The differential diagnosis of minor salivary gland tumors includes basal cell adenoma, adenoid cystic carcinoma, and basaloid squamous cell carcinoma. (3) It is particularly a challenge to distinguish basal cell adenocarcinoma from basal cell adenoma. As previously mentioned, both may share similar architectural and cytologic features. Diagnosis of basal cell adenocarcinoma hinges on the identification of invasion into adjacent tissue. Vascular and perineural invasion are often seen in basal cell adenocarcinoma.

Adenoid cystic carcinoma must be differentiated from basal cell adenocarcinoma for prognostic values. Basal cell adenocarcinoma lacks the cribriform pattern and pseudocysts of amorphous, basophilic material characteristic of adenoid cystic carcinoma. (6) Also in favor of solid adenoid cystic carcinoma is a high mitotic index with necrosis. The cellular features of adenoid cystic carcinoma include pale to clear cells with irregular, angulated nuclei compared with the round to oval eosinophilic cells and round nuclei of basal cell adenocarcinoma. (6)

Basaloid squamous carcinoma must also be considered in the differential diagnosis. Basaloid squamous carcinoma is usually located in the hypopharynx, base of tongue, and supraglottic larynx, regions in which basal cell adenocarcinoma is rarely found. (3) Unlike basal cell adenocarcinoma, basaloid squamous carcinoma shows squamous differentiation that involves the mucosal epithelium, which may demonstrate dysplasia, carcinoma in situ, or invasive squamous cell carcinoma. (6)

CURRENT TREATMENT AND PROGNOSIS

Basal cell adenocarcinomas are low-grade carcinomas that rarely cause distant metastasis. They are locally destructive with a propensity to recur. Surgical excision with a wide margin to ensure complete removal has been suggested as the primary treatment for basal cell adenocarcinoma. (3) Enucleation or curettage is to be avoided. Radiotherapy has been proposed for lesions in the minor salivary glands because of the higher likelihood of vascular and neural invasion. (4) Radiotherapy has also been used for tumors with a diffuse infiltrating pattern to adjacent tissue. (3) A review by Parashar et al (3) showed that about half (8/17) of the patients with available information experienced tumor recurrence, and 2 of 17 patients developed metastases to the regional lymph nodes. Of the 17 patients, 2 died of disease; both of them had a recurrence of disease and died 4 years following the initial diagnosis. (4) Other authors suggest that the recurrence rate is about 25% to 30%, and approximately 10% metastasize to regional lymph nodes or distant organs. (7) It is necessary to differentiate basal cell adenocarcinoma from other basaloid cell tumors because of the differences in prognosis and potential differences in treatment.

Very little is known about the genetic makeup of basal cell adenocarcinoma. The role of specific chromosomal aberrations remains unclear, and additional studies are needed to determine important chromosomal deviations in the pathogenesis of these tumors. (7)

Accepted for publication April 17, 2007.

References

(1.) Seifert G, Sobin LH, eds. Histological Typing of Salivary Gland Tumours. Berlin, Germany: Springer-Verlag; 1991. World Health Organization International Histological Classification of Tumours. 2nd ed.

(2.) Barnes L, Eveson JW, Reichart P, Sidransky D, eds. Pathology and Genetics of Tumours of the Head and Neck. Lyon, France: IARC Press; 2005. World Health Organization Classification of Tumours; vol 9.

(3.) Parashar P, Baron E, Papadimitriou J, Ord R, Nikitakis N. Basal cell adenocarcinoma of the oral minor salivary glands: review of the literature and presentation of two cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007; 103:77-84.

(4.) Jayakrishnan A, Elmalah I, Hussain K, Odell EW. Basal cell adenocarcinoma in minor salivary glands. Histopathology. 2003;42:610-614.

(5.) Thompson LDR. Head and Neck Pathology. 1st ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2006:363-365. Goldblum JR, series ed. A volume in the series Foundations in Diagnostic Pathology.

(6.) Ellis GL, Auclair PL, Basal cell adenocarcinoma. In: Rosai J, Sobin LH, eds. Tumors of the Salivary Glands. Washington, DC: Armed Forces Institute of Pathology; 1996:257-267. Atlas ofTumor Pathology; 3rd series, fascicle 17.

(7.) Scholtz A, Hollrigl A, Verdorfer I. Genetic alterations in a basal cell adenocarcinoma of the glandula submandibularis [letter]. Cancer Genet Cytogenet. 2007;172:87-89.

Tisha Farrell, DO; Yilan L. Chang, MD, PhD

From Western Reserve Care System, Northeastern Ohio Universities College of Medicine (Dr Farrell) and the Department of Pathology, St Elizabeth Health Center (Dr Chang), Youngstown, Ohio.

The authors have no relevant financial interest in the products or companies described in this article.

Reprints: Tisha Farrell, DO, Western Reserve Care System, Northeastern Ohio Universities College of Medicine, 500 Gypsy Ln, Youngstown, OH 44501 (e-mail: tfpath@gmail.com).
Gale Copyright: Copyright 2007 Gale, Cengage Learning. All rights reserved.