Basal Cell Carcinoma

 Genes implicated include PTCH1 (Gorlin syndrome),  TP53, SOX9, BMI1, BAX, RMRP






Clinical Issues




• Extremely common: Most common cancer in humans

• Most common in head and neck region (up to 80% of cases)

• Prognosis usually excellent, most cases cured by excision

• More aggressive subtypes, including infiltrative, micronodular, desmoplastic, and basosquamous, have higher rate of recurrence and low risk of metastasis

• Treated by complete excision or electrodesiccation and curettage


Microscopic




• Proliferation of nodules, nests, and cords of basaloid cells with peripheral palisading, stromal retraction artifact, and mucinous material

• Numerous mitotic and apoptotic figures typically present

• Cells show enlarged hyperchromatic nuclei with inconspicuous nucleoli and scant amounts of cytoplasm

• Superficial multicentric type: Superficial nests attached to epidermis separated by areas of uninvolved epidermis

• Nodular type: Large, rounded, predominantly dermal-based nests with prominent peripheral palisading

• Micronodular type: Predominantly dermal-based infiltrative proliferation of small nests

• Infiltrative type: Small cords and nests, often deeply invasive

• Desmoplastic/sclerosing/morpheaform type: Infiltrative strands and nests associated with dense sclerotic stroma


Top Differential Diagnoses




• Squamous cell carcinoma

• Actinic keratosis (on superficial shave biopsy)

• Follicular neoplasms (trichoepithelioma and trichoblastoma)

• Merkel cell carcinoma

image
Clinical Photograph of Basal Cell Carcinoma
Clinical photograph of a large facial basal cell carcinoma (BCC) shows areas of ulceration and granulation-like tissue surrounded by a raised border image. (Courtesy S. Yashar, MD.)


image
Basal Cell Carcinoma at Low Magnification
Low magnification shows a large nodular- and micronodular-type BCC with diffuse overlying ulceration and dense serum crust containing degenerating neutrophils.

image
Basal Cell Carcinoma at High Magnification
High magnification of a nodular BCC shows a sheet-like proliferation of atypical basaloid cells with high nuclear:cytoplasmic ratios and numerous apoptotic image and mitotic figures image.

image
Basal Cell Carcinoma: Micronodular Type
Histologic section of a micronodular-type BCC shows a proliferation of small, infiltrative nests of basaloid cells with a prominent retraction artifact image in a somewhat sclerotic-appearing stroma.


TERMINOLOGY


Abbreviations




• Basal cell carcinoma (BCC)


Synonyms




• Basal cell epithelioma (BCE)

• Trichoblastic carcinoma (not well accepted and should be discouraged)


Definitions




• Low-grade malignancy of basaloid-appearing keratinocytes


ETIOLOGY/PATHOGENESIS


Multifactorial




• Related to sun exposure (vast majority of cases)
image Some cases may also be associated with radiation, immunosuppression (organ transplantation), burn scars

– These cases tend to be more aggressive

• May actually be derived from follicular stem cells (hence, rationale for term trichoblastic carcinoma)


Genetics




• Rare cases are associated with genetic syndromes including nevoid BCC (Gorlin) syndrome, xeroderma pigmentosum, Basex syndrome, Rombo syndrome, and McKusick syndrome
image Genes implicated include PTCH1 (Gorlin syndrome),  TP53, SOX9, BMI1, BAX, RMRP


CLINICAL ISSUES


Epidemiology




• Incidence
image Extremely common: Most common cancer overall in humans when skin cancers are included

– Accounts for 70% of primary cutaneous malignancies

• Age
image Typically older adults; few cases in young adults
– If in child, should consider genetic syndrome

• Sex
image Slightly greater incidence in male patients

• Ethnicity
image Caucasian/light-skinned individuals

image Rare in individuals with darker skin types


Site




• Most common in head and neck region (up to 80% of cases)
image ~ 15% occur on trunk and shoulders

image Very rare cases involve lips, breast, axillae, groin, inguinal region, and genitalia


Presentation




• Typically papular, plaque-like, or nodular lesion
image Often present as pearly, translucent papule with telangiectasia

image Larger lesions often ulcerated with bleeding &/or overlying crusting

image Minority of cases are pigmented, more often in Asians and Africans


Treatment




• Surgical approaches
image Complete excision or electrodesiccation and curettage

image Mohs micrographic surgery often used in facial cases


Prognosis




• Usually excellent, cured by local excision
• More aggressive subtypes, including micronodular, infiltrative, desmoplastic, and basosquamous, have higher rate of recurrence and increased (but still very low) risk of metastasis

image Overall risk of metastasis estimated at 0.05%


MACROSCOPIC


Size




• Variable, small (few mm) to large (several cm)


MICROSCOPIC


Histologic Features




• Tumor is composed of nodules, nests, &/or infiltrative cords
image Overlying ulceration and serum crusting often present in large tumors

• Proliferation of small basaloid cells with peripheral palisading

• Stromal retraction artifact
image Between tumor cells and stroma

• Mucinous material often is present in stroma

• Numerous mitotic and apoptotic figures in most cases

• Cells show enlarged, hyperchromatic-staining nuclei with inconspicuous or small nucleoli and scant eosinophilic cytoplasm

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Basal Cell Carcinoma
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