What is Squamous Cell Carcinoma?

Squamous Cell Carcinoma (SCC) is a form of skin cancer that consists of “nests” of squamous epithelial cells originating in the epidermis and infiltrating the dermis. This keratinocytic form of skin cancer often occurs in conjunction with actinic keratosis or within existing squamous cell carcinoma in situ. Although recognizing SCC is relatively straightforward, the determination of whether the cancer is present in situ or if the lesion has become invasive requires extensive examination.

Variations of Squamous Cell Carcinoma

Several types of benign epithelial changes and infections closely mimic SCC. These include viral changes, eccrine squamous syringometaplasia, pseudoepitheliomatous hyperplasia, keratoacanthoma, and reactive atypia. The variations and differential diagnoses of SCC and other cancers may require extensive testing to distinguish and make a definitive diagnosis.

Clear Cell SCC: Cells contain glycogen, which compresses the nucleus and causes lateral displacement

Acantholytic SCC: Uncommon; Central acantholysis leads to appearance of gland formation

Spindle Cell SCC: Relatively common, occurs in areas exposed to sun, trauma, radiation, and in organ transplant patients

Inflammatory SCC: Poorly differentiated squamous nests surrounded by dense lymphocytic stromal infiltrate; Increased metastatic potential

Desmoplastic SCC: Nests and strands with high desmoplastic stromal reaction; Increased risk of recurrence and metastases

Pseudovascular SCC: Common amongst men on body parts exposed to the sun; High recurrence, metastatic, and mortality rate

Pseudohyperplastic SCC: Occurs on penis; Non-verruciform; Associated with lichen sclerosis

Basaloid SCC: Located in anogenital and oropharynx regions; Associated with HPV infection

Pigmented SCC: Epithelial tumor cells, macrophages, and dendritic melanocytes contain melanin (Compare to squamomelanocytic tumor, which contains both SCC and melanoma characteristics)

Verrucous Carcinoma: Rare (except for HPV-related anal lesions); Higher rick of recurrence; Rare metastases

Adenosquamous/Mucoepidermoid Skin Carcinoma: Affects head and neck; Sparse glandular differentiation

Follicular SCC: Typically located on head and neck (forms in upper hair follicles)

Infiltrative SCC: Small nests/strands/cells infiltrating a fibrous or mucinous dermis

Metaplastic SCC/Carcinosarcoma: Extremely rare biphasic tumor includes malignant epithelial and mesenchymal components

Squamous Cell Carcinoma in Situ Treatment

Epidermal alteration and disorderly maturation can be viewed microscopically when examining tissue for squamous cell carcinoma in situ (SCCIS). Like SCC, many variants and differential diagnoses exist. Pigmented, pagetoid, and clear cell SCCIS, as well as Paget’s disease, Bowenoid papulosis, and clonal seborrheic keratosis share some characteristics and must be evaluated for diagnosis prior to the commencement of treatment.

Contact Allegheny Advanced Dermatology Center to schedule an appointment. Call: (814) 944-7109.