|Year : 2007 | Volume
| Issue : 2 | Page : 56-59
Basal cell adenocarcinoma: Report of a case affecting the submandibular gland
Ruchi Sharma1, Susmita Saxena1, Rani Bansal2
1 Department of Oral Pathology and Microbiology, Subharti Dental College, Meerut, Uttar Pradesh, India
2 Department of Pathology, Subharti Medical College, Meerut, Uttar Pradesh, India
Department of Oral Pathology and Microbiology, Subharti Dental College, Meerut, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Basal cell adenocarcinoma is a well-recognized salivary gland adenoma, but in recent years there have been occasional reports of malignant basal cell tumors of major salivary glands. We here present a case report of one such basal cell adenocarcinoma arising in the submandibular salivary gland and discuss the differentiation from a basal cell adenoma. The relevant literature is discussed.
Keywords: Basal cell adenocarcinoma, basal cell adenoma, submandibular salivary gland
|How to cite this article:|
Sharma R, Saxena S, Bansal R. Basal cell adenocarcinoma: Report of a case affecting the submandibular gland. J Oral Maxillofac Pathol 2007;11:56-9
|How to cite this URL:|
Sharma R, Saxena S, Bansal R. Basal cell adenocarcinoma: Report of a case affecting the submandibular gland. J Oral Maxillofac Pathol [serial online] 2007 [cited 2020 Aug 6];11:56-9. Available from: http://www.jomfp.in/text.asp?2007/11/2/56/37382
| Introduction|| |
Basal cell adenocarcinoma (BCAC), a recent addition to the subtypes of salivary gland carcinoma, was included in the 1991 World Health Organization classification of salivary gland neoplasms. Although there have been occasional references in the literature over the past 30 years to malignant basaloid tumors, malignant transformation of basal cell adenoma and salivary gland carcinomas associated with basal cell adenoma, BCAC has only recently been characterized. 
Before the term was universally accepted, this tumor was reported under a variety of names, including malignant basaloid tumor, malignant basal cell tumor, hybrid basal cell adenoma/ adenoid cystic carcinoma, basaloid salivary gland carcinoma and atypical monomorphic adenoma. Ellis and Gnepp defined the histologic features of this tumor in 1988, and Ellis and Wiscivitch in 1990 defined the clinicopathologic features of basal cell adenocarcinoma in their study of 29 cases. 
BCAC of the salivary gland, a rare neoplasm that occurs mostly in the major salivary glands, particularly in the parotid gland, comprises 1.6% of all salivary gland neoplasms and 2.9% of malignant salivary gland neoplasms. BCAC is a tumor similar to basal cell adenoma (BCA) except that it grows in an invasive destructive fashion, often with perineural and/or vascular invasion but without histologic evidence of preexisting basal cell adenoma.  They are divided on the basis of growth pattern into the following four subtypes: solid, trabecular, tubular and membranous; of these, the solid subtype is the most common. 
In this paper, we are presenting a case, reported to the Department of Oral Pathology and Microbiology, Subharti Dental College, Meerut, diagnosed as basal cell adenocarcinoma, to describe clinicopathological features of this rare neoplasm.
| Case Report|| |
A 53-year-old female patient reported with swelling in lower right region of face since six months. Swelling was also accompanied with pain in the involved region.
There was a history of extraction of lower anterior teeth one month ago associated with sudden increase in size of swelling and numbness. On examination, swelling was present on right side of the face, extending from the right submandibular region to the left submandibular region but more obvious on the right side. Intraoral swelling was present, extending from mandibular right first premolar region to mandibular left canine region [Figure - 1]. Submandibular lymph nodes were tender, firm and fixed to underlying tissue.
Radiography revealed no abnormality. On the basis of clinical features, lesion was thought to be a salivary glandular lesion with possibility of pleomorphic adenoma. Fine needle aspiration cytology was done from right submandibular region. Smear showed clusters of monolayered sheets of small round-to-oval cells, mostly monomorphic; and having hyperchromatic nuclei, without nucleoli, and scanty cytoplasm. Occasional bizarre nuclei were also seen. Mitotic figures and anaplasia could not be appreciated [Figure - 2]. Features were suggestive of basal cell adenoma with suspicion of malignancy. However, histopathological examination was necessary to confirm it.
Incisional biopsy was advised preoperatively. The biopsy specimen sent for histopathology was creamish brown in color, and firm in consistency. Microscopically, the section showed sheets and strands of proliferating monotonous basaloid cells having hyperchromatic nuclei. Two types of basaloid cells were observed - dark basophilic cells towards the periphery and pale basophilic cells towards the center of the proliferation. Encapsulation could not be identified, and lesion seemed to be penetrating deep till the edge of the specimen. Intervening connective tissue stroma was fibrous with hemorrhagic areas. Tumor tissue showed a haphazard pattern of proliferation with invasion into deeper tissue with some attempt at glandular arrangement. As such, cellular atypia or mitotic figures could not be appreciated. Perineural infiltration of tumor tissue was evident [Figure - 3],[Figure - 4]. Based on the sheet and interconnected strand-like proliferation of basaloid cells, the histopathologic diagnosis of basal cell adenocarcinoma (solid pattern intermixed with trabecular pattern) was given.
| Discussion|| |
Basal cell adenocarcinoma (BCAC) of salivary gland is considered to be the malignant counterpart of basal cell adenoma.  Reports of malignant basaloid salivary gland tumors are extremely rare.  Ninety percent of cases reported are in the major salivary glands, usually the parotid. Four cases have been reported in the submandibular gland till 1996.  No further case reports could be found in the literature. Present case adds up to the incidence of reported cases of basal cell adenocarcinoma of submandibular salivary gland.
No predilection for occurrence of basal cell adenocarcinoma in either men or women is apparent. Eighty percent of the patients are over 50 years, with the average age of 60 years. The present case has been reported in a woman aged 53 years. Swelling is the principal symptom, but pain or tenderness occasionally may be an associated complaint. Occasionally, the swelling has been described as rapid in onset, but this has no prognostic significance. In the present case also, the patient reported swelling which developed rapidly (within six months) with associated pain. 
Histologically, BCAC can be divided into four subtypes: solid, trabecular, tubular and membranous. The solid pattern is characterized by contiguous tumor cells arranged in islands and masses within the fibrous connective tissue stroma. These tumor islands can be round to oval or large irregular masses. The present case has shown the proliferation of basaloid cells in the form of sheets or irregular masses showing similarity with solid pattern of BCAC.
The membranous type is distinguished by thick, eosinophilic, periodic acid schiff positive hyaline laminae that surround and separate one tumor nest from another and may create a jigsaw puzzle image in portions of tumor. 
Trabecular type is characterized by anastomosing cords and bands of basaloid epithelial cells which may be likened to the configurations shaped like Chinese characters that are formed by bony trabeculae in fibrous dysplasia of bone. Conspicuous small lumina or pseudolumina characterize the tubular type of BCAC.  Sheet-like proliferation of the present case was intermingled with interconnecting strands or cords of basaloid epithelial cells, due to which diagnosis of solid pattern intermixed with trabecular pattern of BCAC was justified.
A solid pattern is predominant in about two-thirds of the tumors. The membranous type is the second most frequent and comprises about 20% of these tumors. The trabecular and tubular types are occasionally the dominant patterns. 
The growth of tumor in relation to surrounding tissues is the key feature used to distinguish adenoma from carcinoma for basaloid salivary gland neoplasms.  Presence of perineural invasion and the histopathologic appearance of the cells with its invasive nature prompted the distinction between BCAC and basaloid adenoma in the present case.
Two forms of epithelial cells are observed and are usually intermingled with one another. One form is small, round cell with scanty cytoplasm and a dark basophilic nucleus. The other form is a large, polygonal-to-elongated cell with eosinophilic cytoplasm and a large, pale basophilic nucleus. In both types of cells, the cell-to-cell boundaries are distinct. Frequently, the small dark cells are located peripherally to the larger pale cells and produce palisading of the nuclei of cells along epithelial stromal interface. The amount of supporting collagenous stroma can vary from inconspicuous to extensive.  The present case has shown both forms of cells. At places, dark basophilic cells were located at the periphery of epithelial islands, with pale basophilic cells present towards center.
Ultrastructurally, BCAC is composed of luminal and nonluminal cells. The nonluminal cells show frequent desmosomes and tonofilaments or, occasionally, myofilaments and dense bodies; the latter features indicate the myoepithelial nature of these cells. The luminal cells have numerous intercellular canaliculi and prominent microvilli and numerous secretory granules. The tumor shows excessive basal lamina production surrounding the tumor cell nests. Redundant basal lamina and glycosaminoglycans can accumulate intracellularly in BCAC. 
The staining patterns of cytokeratin, anti-smooth muscle actin and S-100 protein varies with the architectural type of BCAC.  In the present case, since the histologic features were strongly suggestive of BCAC, immunohistochemistry was not performed.
BCAC can be confused with adenoid cystic carcinoma (ACC); but amorphous, pale basophilic material located in the pseudocysts of ACC is not encountered in BCAC. Also, the cytologic features are more uniform with more hyperchromatic and angular nuclei in ACC than round and ovoid nuclei in BCAC. The cribriform pattern, which is commonly seen in ACC, is distinctive and not found in BCAC.  Due to the above differences, ACC was ruled out during diagnosis.
Another basaloid tumor showing similarity with BCAC is basaloid squamous cell carcinoma (BSCC), a distinct variant of squamous cell carcinoma. The basaloid component of BSCC arranged in a solid or trabecular pattern may emulate that of basal cell adenocarcinoma. In this instance, the key distinguishing feature is the presence of squamous differentiation and invasive squamous cell carcinoma, both of which form an integral component in BSCC but are not features of basal cell adenocarcinoma.  The diagnosis of BSCC was also ruled out in the present case due to the absence of squamous cell component, which should be present to give the diagnosis of BSCC.
Although, incidence of BCAC in submandibular salivary gland is low, one should consider this entity as a differential diagnosis while reporting for the submandibular salivary gland pathology.
It is clear that these neoplasms do not have a malignant potential to metastasize and lead to death. At present, these are believed to be low-grade adenocarcinomas, with a relatively good prognosis.  BCAC is well controlled locally, although local recurrence was reported in 28% of the cases of Ellis and Wiscovitch.  The surgeon should aim for complete surgical removal of the tumor during the first surgical procedure to provide the best chance for survival. 
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]