ADENOME A Basal cell
Basal cell adenoma 2008
General
It is a benign epithelial tumor composed mainly of basaloïdes cells. The demarcation between epithelial proliferation and tumor Strom is very clear and the tumor is devoid of the chondromyxoid tissue characteristic of the pleomorphic adenoma. According to the architectural organization, there are several types: massive, trabecular, tubular or membranous.
Incidence: 1.5% of salivary gland tumours and 2.4% of benign tumours. Parotid in 75% of cases and upper lip in 8% of cases. The average age is 58 years. There is a feminine predominance. Membrane-type basal cell adenomas are sometimes associated with the presence of a adnexal skin tumor. It is most often a skin cylindroma, but other tumors have been described: Trichoépitheliome, Trichilemmomas, Spiradenoma eccrine.
Macroscopy
Single Nodule well limited, "Encpsulé " not fixed and measuring less than 3cm with sometimes cystic reshuffles.
The membranous architectural type is most often poorly limited and multifocal.
Microscopy
Monomorphic appearance by predominance of basaloïdes cells. They are small round, oval and pale cytoplasmic and poorly constrained circular cells that can correspond either to real basal cells or to ductales or myoepithelial cells. The term Basaloïde allows to group these different types of cell that one cannot easily distinguish without immunohistochemistry. Two morphological types of basaloïdes cells are described: dark basaloïdes cells have a hyperchromatic nucleus and a sparse cytoplasm. They are arranged in a palisade way on the periphery of the massif. The clear basaloïdes cells have a pale nucleus and abundant cytoplasm. They are located in the center of the massif. There are also some ductales cells that form small glandular lumens, particularly in the tubular type.
Architectural TYPES
Solid Type
The cells can be grouped in clumps, in wide spans more or less anastomotic, in large or small nodules (insular-type architecture). The stroma is collagenous dense. There may be areas of metaplasia squamous sometimes incomplete (vortices) or mature (horny globes). Cystic reshuffles are common in particular at the subcapsular level.
Type trabecular
The cells form thin spans anastomotic in a loose strom. The palisade appearance of dark basaloïdes cells is less pronounced than in the massive type. In some cases there are many more or less cystic ductales formations. It is this form that poses a differential diagnosis problem with the Canalicular adenoma.
Tubular Type
It is in this type, the rarest, that ductale differentiation is most pronounced. Some authors group these two forms under the type Tubulo-trabecular.
Membranous Type
Thick bands Hyaline not + surround each cell massif which gives a low magnification a puzzle aspect. These strips correspond to excessive basal membrane production. Hyaline material can also be observed in intercellular situations in the form of balls hyaline P as + more or less coalesce. These aspects can during the examination extemporaneous evoke a cystic adenoid carcinoma.
More often than not, several architectural types are represented in the same tumor which is then classified according to the prevailing architectural mode. It is especially important to distinguish the membranous type from other architectural types because it involves association with skin tumors and a pejorative prognosis.
Immunohistochemistry
Cytokeratin: Constant positivity but the number of cells marked is very variable.
Anti-actin, anti-PS-IOO and anti-dementia: positivity in most basal cell adenomas, at the level of basaloïdes cells located on the periphery of the massifs.
The anti-EMA and anti-ACE mark the small ductales formations.
Anti-myosin and anti-GFAP sometimes mark a few cells.
Differential diagnosis
Basal carcinoma
If the skin is infiltrated or very close to the basal cell adenoma, it may be mistaken for basal carcinoma.
Cystic adenoid carcinoma
The predominance of basaloïdes cells in cystic adenoid carcinoma of massive form, and inversely cribriformes focal aspects or accumulation of basal membranes in basal cell adenomas can make the diagnosis Thorny differential. The following criteria must be helped:
Basal cell adenoma
Cystic adenoid carcinoma
Limitation
Good limitation
Gross infiltration and
Encapsulation
Microscopic
Nerve infiltration
Not
Frequent
Cribriform Architecture
Rare and focal length
Frequent
Anisocaryose
Not
Yes
Shape of the nuclei
Rounded
Angular
Clear cells
Not
Yes
Metaplasia squamous
Yes
Not
Necrosis
Rare.
Frequent
Basal cell adenocarcinoma
mitotic activity greater than 3 mitoses for 10 fields is highly suspicious, but it is the infiltration (fatty, muscular, cutaneous, or bony, nerve or vascular) that indicates the malignancy of this lesion.
Pleomorphic adenoma in its cell variant
Epithelial massifs that characterize the pleomorphic adenoma. A strong expression of GFAP is also in favor of a pleomorphic adenoma. A weak expression of GFAP does not provide any element for differential diagnosis.
Canalicular adenoma
Basal cell adenoma
Canalicular adenoma
Favorite Site
Parotid (75%)
Upper lip (75%)
Upper lip (6%)
Oral mucosa (12%)
Submaxillary (5%)
Average Age
58 years
65 years (Adult only)
Association
Similarity and association with T
No
(or diathesis)
Eccrine Skin and Cylindromes
"Dermal analoge tumor"
Cells
Basaloïdes
Low cylindrical
span thickness
Variable
Single cell rows sometimes
Anastomosing
Stroma
Mostly dense
Little visible finely fibrillar
Very richly vascularized
Prognosis and treatment
Except for the membranous type, the recurrences are rare. A total resection of the lesion is therefore practised in a conservative manner. The membranous type is to be individualized from other types. It re-offends in 25% of cases and undergoes a carcinomatous transformation in 28% of cases compared to 4% for other architectural types. This transformation most often corresponds to a basal cell adenocarcinoma, but it can also be another tumor type. In addition, an association with skin tumours (Cylindroma + + +) is noted.
Pleomorphic adenomas, basal cell adenomas, and Myoépithéliomes X_font are part of the same tumor spectrum. There are forms of passage between epithelial cells and myopithéliales making their distinction immunohistochirnique sometimes difficult.
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