Prsentation Clinique

F 55 ans, lsion du front.

Pathologie:

 Lsion noplasique infiltrant le derme, tale, forme de   traves pithliales grles, parfois appendues l'piderme. Elle est constitue de cellules basaloides, entoure d'une raction desmoplasique stromale.

Diagnostic Propos:

CARCINOME BASOCELLULAIRE, SCLRODERMIFORME.

Basal cell carcinoma (Akerman's Surgical Pathology)

General features

Basal cell carcinoma derives its name from the cytologic similarity of the tumor cells to the normal basal cells of the epidermis and the traditional belief that it arises from them. In our opinion, all basal cell carcinomas attempt to differentiate along adnexal structures (particularly pilosebaceous units), but most of them remain at a stage so primitive as to render this recognition not immediately apparent. However, the belief that basal cell carcinomas represent primitive "adnexal" carcinomas has been voiced over the years by several authors.

Basal cell carcinoma is the most frequent form of skin cancer; it occurs predominantly on the sun-exposed skin in direct proportion to the number of pilosebaceous units present therein, a feature supporting the previous histogenetic interpretation. Fair-skinned, blue-eyed persons engaged in outdoor occupations suffer a higher incidence of these tumors.Synchronous and metachronous tumors are frequent. Exceptionally, children and young adults are affected. 
Basal cell carcinomas may also develop in sunlight protected skin, in nevus sebaceous of Jadassohn, in the lower leg in association with chronic venous stasis and other preexistent conditions, and following
arsenic ingestion, xray exposure, skin injury, chickenpox scars, tattoos, hair transplantation scars, and immune suppression.
The clinical appearance of basal cell carcinoma is as variable as its histologic patterns. Nodular, ulcerative, superficial, erythematous, multicentric, and sclerosing or morphealike forms occur.

Microscopic features

Basal cell carcinomas arise from basally located cells of the epidermis and pilosebaceous units and differentiate incompletely in the direction of adnexal (primarily pilar) structures. Epidermal attachment is present in nearly all cases. The tumors may have solid, cystic, adenoid, keratotic, pigmented, infiltrating, and sclerosing (morphea-like) patterns. The keratotic pattern probably represents an expression of differentiation toward hair follicles, has no clinical significance, and should be distinguished from
so-called basosquamous carcinoma.
The nests of basal cell carcinoma show prominent palisading and are surrounded by a typical loose stroma, which contains myofibroblasts and often exhibits mucinous change. Cleft-like retraction spaces, some of artifactual nature and others resulting from the accumulation of stromal mucin, are often seen between the epithelial nests and the stroma. Melanin can accumulate in dermal microphages between the tumor nests and result in a "pigmented" appearance clinically . Intercellular amyloid material is not infrequent, sometimes accompanied by the deposition of immunoglobulins. Oval to spindle tumor cells with hyaline eosinophilic cytoplasm have been found in a few of the cases and interpreted by some as evidence of myoepithelial differentiation. Mitotic activity (sometimes accompanied by atypical forms), marked atypia with appearance of bizarre ("monster") tumor cells, and giant cell formation may occur, but there is no convincing evidence that any of these features carries prognostic significance.
Rarely, matrical (shadow cell formation) or eccrine differentiation is seen in otherwise typical basal cell
carcinoma, further supporting the close relationship of these tumors with adnexal structures. Perineurial or
endoneurial invasion by tumor cells is rarely present.99 Sometimes, a basal cell carcinoma is seen adjacent to a benign menaloyctic nevus, the juxtaposition being a coincidental event.
The differential diagnosis of basal cell carcinoma includes the areas of highly organoid basaloid proliferation sometimes seen on top of dermatofibromas and the more atypical foci of basaloid proliferation that may be found in association with actinic keratosis and Bowen's disease  

Immunohistochemical and other special techniques

Immunohistochemically, the cells of basal cell carcinoma are positive for keratin (particularly
low-molecular-weight type118,121,123), but usually negative for EMA, CEA, and involucrin. The basement membrane that surrounds the tumor nests reacts with antibodies against laminin, types IV and V collagen, and bullous pemphigoid antigen. The pattern of staining for these markers tends to be attenuated and discontinuous, as an expression of the disruption of this structure.This feature is more prominent in the agressive tumors.
A suggestion has been made some years ago to the effect that basal cell carcinomas may show
neuroendocrine differentiation; although the relatively common finding of argyrophilia may seem to support
this contention, immunoreactivity for neuroendocrine markers such as chromogranin or neuron-specific enolase is an exceptionally rare event.
It has been shown that most basal cell carcinomas stain for BerEP4 whereas most squamous cell carcinomas do not; the reverse is true regarding the expression of Ulex europaeus agglutinin I lectin-binding sites. More than 80% of basal cell carcinomas overexpress p53 protein. Clonal chromosome alterations have been found in some cases of basal cell carcinoma, but a consistent pattern has not yet emerged. Widely invasive and/or aggressive (recurring/metastasizing) basal cell carcinomas have a higher AgNOR count, and a higher incidence of aneuploidy than the others. 

Other microscopic types

Superficial basal cell carcinoma arises in skin with sparse, fine hairs and epidermis that is thin, such as that of the trunk. It grows chiefly in a lateral direction, beneath a relatively flat epidermis, and exhibits a high
recurrence rate.

Basosquamous (metatypical) carcinoma has the general configuration of a basal cell carcinoma, but it also contains atypical squamous cells. This variant is more aggressive than the conventional basal cell
carcinoma; a high proportion of the metastasizing basal cell tumors belong to this type, which should be
distinguished from the keratotic form of basal cell carcinoma.

Granular basal cell carcinoma contains tumor cells with cytoplasmic granules analogous in every way to
those seen in granular cell tumor of the dermis and other locations. No clinical significance is ascribed to
this variety.

Clear cell basal cell carcinoma contains clear cells with prominent cytoplasmic vacuoles; in other
cases the tumor cells may even have a signet ring configuration.

Fibroepithelial tumor (Pinkus' tumor; fibroepithelioma) is a polypoid variant of basal cell carcinoma, often occurring on the back, in which the stroma is very abundant. It has been suggested that the
fibroadenoma-like pattern of this tumor is the result of eccrine duct spread.

Basal cell nevus syndrome (Gorlin's syndrome) is characterized by multiple basal cell carcinomas, palmar pits, calcification of dura, keratinous cysts of the jaws, skeletal anomalies, and occasional abnormalities of the central nervous system, mesentery, and endocrine organs. Microscopically, the basal cell carcinomas exhibit a broader spectrum of subtypes than the sporadic tumors. The syndrome should be suspected when basal cell carcinomas are seen in young persons who have multiple tumors, many of which are of the superficial multicentric type and in which osteoid is an occasional finding.

Infundibulocytic basal cell carcinoma is a variant of basal cell carcinoma in which evidence of hair follicle differentiation is much more evident and advanced than in the ordinary type; it could be viewed as being situated in between the latter and trichoepithelioma in terms of the differentiation spectrum.

Spread and metastases

Basal cell carcinoma usually grows in a slow and indolent fashion. However, if untreated, the tumor may
invade the subcutaneous fat, skeletal muscle, and bone ("ulcus rodens"). Tumors of the face may invade skull, nares, orbit, or temporal bone via the auditory canal. They can thus reach the central nervous system and produce a lethal meningitis. Microscopically, the locally more aggressive tumors tend to show loss of
peripheral palisading and a dense, fibrous stroma rather than a loose stroma. In terms of location, local
recurrence is more common in tumors of the nasolabial fold, inner canthus, and postauricular region. This is probably the combined result of the highly irregular infiltrative pattern that these tumors often exhibit, and the fact that in these locations the distance to the surgical margins tends to be rather close. In general, the
microscopic appearance of the recurrence is not substantially different from that of the original tumor.
Distant metastases are extraordinarily rare, but over 100 cases have been reported. This includes
cases associated with the basal cell nevus syndrome. About 60% to 75% of these metastases involved the regional lymph nodes, and the others affected organs such as lung, bone, and liver. Metastases in basal cell carcinoma are more likely in the basosquamous types, in those with perineurial spread, and in tumors located on sunlightprotected skin.

Treatment

Excision, curettage and desiccation, and irradiation used appropriately cure most basal cell
carcinomas. Even when these tumors extend to the margin of surgical excision (an occurrence of
approximately 5% in large series), only one third will show evidence of recrudescence over the ensuing 2 to 5 years. Thus immediate reexcision is not always indicated under these circumstances. Actually, it has been suggested that evaluation of the pattern of tumor growth (widely dispersed vs. tightly clustered nests) is a better predictor of local recurrence than presence or absence of tumor at the surgical margins.

Recurrent basal cell carcinomas can be treated with radiation therapy or surgical reexcision. In some
institutions, these recurrent tumors (and increasingly, many others, whether recurrent or not) are being treated by a procedure known as Mohs' micrographic surgery.1 The features that allegedly render this a special procedure are the following:

1.The use of "chemical cauterization" with zinc chloride paste. This practice, initially recommended by
Mohs himself, has largely since been abandoned in favor of the conventional scalpel.

2."Microscopically controlled." This is an elegant way of expressing the fact that the adequacy of the
surgical margins is checked by frozen section, a practice that has been in existence for almost a century.

3."En face" orientation of the specimen to be frozen. Once again, this is hardly a novelty in histology or
pathology, the technique having been described over a century ago. Depending on the circumstances, it
may provide more information that the conventional vertical section, or it may not; it is certainly more
difficult to interpret (as all tangential sections are), and it may be very misleading.

4."The Mohs surgeon acts as his own pathologist." In other words, the entire procedure of cutting,
staining, and interpreting the frozen sections from the various margins is done by the surgeon himself,
with the aid of a technician. This is not the place to discuss the medicolegal, quality assurance, and
financial conflicts of interest that this policy raises; suffice it to say that they are of great proportions.

Somebody has commented that the statements made by many Mohs surgeons regarding the merits,
superiority, and uniqueness of their technique have alienated "the great majority of dermatologists, plastic
surgeons, [and] head and neck surgeons." I would like to add "pathologists" (at least one of them) to that
list