Squamous Cell Carcinoma (and Variants)



Squamous Cell Carcinoma (and Variants)


David Cassarino, MD, PhD










Clinical photograph shows an extensive SCC arising on the distal foot in a patient with a history of previous burn injury. (Courtesy S. Yashar, MD.)






Moderately differentiated invasive SCC shows prominent keratin pearls image and a sclerotic stroma with scattered inflammatory cells.


TERMINOLOGY


Abbreviations



  • Squamous cell carcinoma (SCC)


Synonyms



  • Epidermoid carcinoma


  • Sarcomatoid carcinoma/spindle cell carcinoma/carcinosarcoma/metaplastic carcinoma


  • Acantholytic/adenoid/pseudoglandular SCC


  • Verrucous carcinoma (well-differentiated variant)


  • Keratoacanthoma (KA) (well-differentiated variant, regresses spontaneously)


Definitions



  • Malignant tumor of squamous keratinocytes


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Most cases are related to UV radiation


  • Some cases are likely related to chronic inflammation (i.e., SCC arising in burns, lupus, lichen planus)


  • Previous radiation therapy is implicated in some cases, usually associated with more aggressive SCC


  • Chronic wounds and burn scars also can be associated with high-risk SCC


  • HPV is associated with some cases



    • Especially verrucous carcinoma (low grade) and SCC in immunosuppressed patients (high grade)


CLINICAL ISSUES


Epidemiology



  • Age



    • Usually in the elderly, especially solar-related lesions


    • However, can present in a wide age range (34-95 years)



      • Rare cases in children (should prompt genetic studies)


  • Gender



    • Slightly more common in males, overall


Presentation



  • Slow-growing papular, nodular, or plaque lesion


  • Often arises in sun-damaged skin (head and neck tumors)



    • Vast majority of cases associated with preexisting actinic keratosis (AK)


  • May be ulcerated or bleeding


  • Ear canal and middle ear tumors may present with pain, hearing loss, and discharge


Treatment



  • Surgical approaches



    • Complete surgical excision is optimal and definitive therapy



      • Mohs surgery has been shown to be highly effective for most tumors


  • Drugs



    • If patients are not surgical candidates, topical chemotherapeutics or immunomodulators may be used


  • Radiation



    • May be used for very advanced cases where surgical therapy is not curative


Prognosis



  • Usually excellent in most cases


  • Worse prognosis with poorly differentiated, deeply invasive, or rare aggressive subtypes


  • Site of tumor important for prognosis



    • Lip and ear tumors more aggressive, regardless of degree of differentiation



MACROSCOPIC FEATURES


General Features



  • Papular to nodular or plaque-like lesion; can be exophytic



    • May be ulcerated or hemorrhagic


Size



  • Variable; can be small or large lesions


MICROSCOPIC PATHOLOGY


Histologic Features



  • Proliferation of invasive atypical keratinocytes



    • Cells are present in nests, sheets, and infiltrative cords


    • Often show areas of keratinization (keratin pearls) and squamous eddies


    • Attachments to overlying epidermis in most cases


    • Associated AK is very common; less likely, may be associated with SCC in situ (Bowen disease)


    • Cytologically, cells show abundant eosinophilic cytoplasm and large nucleus with vesicular chromatin and prominent nucleoli


    • Intercellular bridges (desmosomes) should be present on high-power examination


    • Presence of dyskeratotic cells (apoptotic keratinocytes) is reliable sign of squamous differentiation


    • If no definite squamous differentiation is present, immunohistochemistry should be used to confirm diagnosis


  • Degree of differentiation is variable, ranging from well- to moderately to poorly differentiated



    • Amount of keratinization typically decreases and cytologic atypia increases with higher grades


    • Mitotic figures are usually numerous, and atypical forms are found especially in moderately to poorly differentiated cases


  • Multiple variants of differing malignant potential described



    • Low-risk variants include well-differentiated SCC arising in AK, keratoacanthoma, verrucous carcinoma, and tricholemmal (variant of clear cell) carcinoma


    • Intermediate-risk variants include acantholytic (adenoid/pseudoglandular) and lymphoepithelioma-like carcinoma of the skin (LELCS)


    • High-risk variants include spindle cell/sarcomatoid, basaloid, adenosquamous, and desmoplastic



      • Also, radiation, burn scar, and immunosuppression-related SCCs


    • Rare variants of uncertain malignant potential include clear cell SCC, signet ring cell SCC, follicular SCC, papillary SCC, pigmented SCC, and SCC arising from adnexal ducts or cysts


Predominant Pattern/Injury Type



  • Epithelioid/squamoid


Predominant Cell/Compartment Type



  • Squamous cell

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Squamous Cell Carcinoma (and Variants)
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