What is the diagnosis?

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Diagnosis

Squamous Cell Carcinoma

Discussion:

This case is presented for baseline comparison with the two previous cases. Squamous cell carcinoma (SCC) is a malignant tumor of the squamous keratinocytes. Most cases are related to UV radiation, some cases are likely related to chronic inflammation (burns, lupus, lichen planus, radiation therapy). HPV is associated is some cases, especially verrucous carcinoma (low grade) and SCC in immunosupressed patients (high grade). Clinically, SCC usually present as a slow-growing papular, nodular or plaque lesions which may be ulcerated or bleeding. Microscopic examination shows proliferation of invasive atypical keratinocytes attached to overlying epidermis in most cases (associated with actinic keratosis or Bowen’s disease is very common). The tumor cells present in nests, sheets and infiltrative cords. Areas of keratinization (keratin pearls) and squamous eddies are seen. Cytologically, the tumor cells show abundant eosinophilic cytoplasm and large nucleus with vesicular chromatin and prominent nucleoli. Intercellular bridges (desmosomes) should be present on high-power magnification. The presence of dyskeratotic cells (apoptotic keratinocytes) is reliable sign of squamous differentiation. If no definite squamous differentiation is present, immunohistochemistry (HMW-CK) should be used to confirm the diagnosis. Degree of differentiation is variable, ranging from well- to moderately to poorly differentiated. Multiple variants of differing malignant potential are described. Low-risk variants include well-differentiated SCC arising in actinic keratosis, keratoacanthoma, verrucous carcinoma and tricholemmal carcinoma. Intermediate-risk variants include acantholytic (adenoid/pseudoglandular) and lymphoepithelioma-like carcinoma of the skin. High-risk variants include spindle cell/sarcomatoid, basaloid, adenosquamous and desmoplastic. 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. Complete surgical excision is optimal and definitive therapy. If patients are not surgical candidates, topical chemotherapeutics or immunomodulators may be used. Radiation may be proposed for very advanced cases where surgical therapy is not curative. The prognosis is usually excellent in most cases. Worse prognosis is associated with poorly differentiated, deeply invasive or rare aggressive subtypes. Lip and ear tumors are more aggressive, regardless of the degree of differentiation.