Biopsy of a highly differentiated<unk>  of the mouth. Typical<unk>  cells are large with abundant eosinophilic cytoplasm and large, often vesicular, nuclei. Haematoxylin & eosin stain Medical history, physical examination and medical imaging may suggest a<unk> , but a biopsy for histopathology generally establishes the diagnosis. TP63 staining is the main histological marker for<unk> . In addition, TP63 is an essential transcription factor to establish<unk>  cell identity. File:Squamous Cell Carcinoma well differentiated Left upper paraspinal back with adjacent actinic keratosis.Squamous Cell Carcinoma, well differentiated, left upper paraspinal back marked for biopsy with adjacent actinic keratosis File:Squamous Cell Carcinoma Left Lateral Canthus.Squamous Cell Carcinoma, left lateral canthus marked for biopsy File:Squamous Cell Carcinoma Left Ventral Forearm.Squamous Cell Carcinoma, left ventral forearm Classification Cancer can be considered a very large and exceptionally heterogeneous family of malignant diseases, with<unk> s comprising one of the largest subsets. All<unk> C lesions are thought to begin via the repeated, uncontrolled division of cancer stem cells of epithelial lineage or characteristics.<unk> Cs arise from<unk>  cells, which are flat cells that line many areas of the body. Some of which are keratinocytes. Accumulation of these cancer cells causes a microscopic focus of abnormal cells that are, at least initially, locally confined within the specific tissue in which the progenitor cell resided. This condition is called<unk>  in situ, and it is diagnosed when the tumor has not yet penetrated the basement membrane or other delimiting structure to invade adjacent tissues. Once the lesion has grown and progressed to the point where it has breached, penetrated, and infiltrated adjacent structures, it is referred to as "invasive"<unk> . Once a carcinoma becomes invasive, it is able to spread to other organs and cause the formation of a metastasis, or "secondary tumor". Tissue of origin The International Classification of Diseases for Oncology (ICD-O) system lists a number of morphological subtypes and variants of malignant<unk>  cell neoplasms, including: * Papillary thyroid carcinoma (code 8050/3) * Verrucous<unk>  (code 8051/3) * Papillary<unk>  (code 8052/3) *<unk>  (code 8070/3) * Large-cell keratinizing<unk>  (code 8071/3) * Large-cell nonkeratinizing<unk>  (code 8072/3) * Small-cell keratinizing<unk>  (code 8073/3) * Spindle-cell<unk>  (code 8074/3) It is also known as spindle-cell carcinoma,) and is a subtype characterized by spindle-shaped atypical cells. * Adenoid/pseudoglandular<unk>  (code 8075/3) * Intraepidermal<unk>  (code 8081/3) * Lymphoepithelial carcinoma (code 8082/3) Other variants of<unk> Cs are recognized under other systems, such as keratoacanthoma. Other histopathologic subtypes * Erythroplasia of Queyrat * Marjolin's ulcer is a type of<unk> C that arises from a nonhealing ulcer or burn wound. More recent evidence, however, suggests that genetic differences exist between<unk> C and Marjolin's ulcer, which were previously underappreciated. One method of classifying<unk> s is by their appearance under microscope. Subtypes may include: * Adenoid<unk>  (also known as pseudoglandular<unk>  is characterized by a tubular microscopic pattern and keratinocyte acantholysis. * Basaloid<unk>  is characterized by a predilection for the tongue base. * Clear-cell<unk>  (also known as clear-cell carcinoma of the skin) is characterized by keratinocytes that appear clear as a result of hydropic swelling. * Signet ring-cell<unk>  (occasionally rendered as signet ring-cell<unk>  is a histological variant characterized by concentric rings composed of keratin and large vacuoles corresponding to markedly dilated endoplasmic reticulum. These vacuoles grow to such an extent that they radically displace the cell nucleus toward the cell membrane, giving the cell a distinctive superficial resemblance to a "signet ring" when viewed under a microscope. File:SkinTumors-P6070232.Adenoid<unk>  File:SkinTumors-P6020140.Basaloid<unk>  File:SkinTumors-P5290109.Clear-cell<unk>  File:SkinTumors-P5300131.Spindle-cell<unk>
Squamous cell carcinoma
Adenosquamous carcinoma
Sebaceous carcinoma
Mucoepidermoid carcinoma
Basal-cell carcinoma
Ceruminous adenocarcinoma
Epithelioma
Bartholin gland carcinoma