Pathological characteristics of skin cancer

Pathological features of skin cancer:

1. Basal cell carcinoma According to the naked eye appearance of the lesion, basal cell carcinoma can be divided into many subtypes, each with its own different clinical characteristics, histological manifestations, degree of differentiation and biological behavior. The naked eye appearance of basal cell carcinoma varies greatly and is more meaningful than detailed tissue typing. The most common manifestation of basal cell carcinoma is ulcerative nodules on the face; secondly, subcutaneous nodules are often covered by intact epidermis; in addition, there are flat ulcerative lesions, erythematous scaly plaques and hard plaque-like morphology, which are easy to identify. Those with erythematous scaly plaques and hard plaque-like appearance are superficial sclerosing basal cell carcinoma. The common sites and incidence of basal cell carcinoma are the head and neck (85%), and the remaining 15% occur in the trunk and limbs. Basal cell carcinoma can have multiple primary cancers at the same time. In a 5-year prospective study, 36% of 100 patients with basal cell carcinoma developed a second primary cancer.

Microscopic observation: There are clearly bordered tumor cell groups in the dermis, with slightly larger nuclei than normal, oval or long, less cytoplasm, unclear boundaries between cells, and no bridges between cells. Therefore, it seems that many nuclei are densely distributed in a common serous fluid, and there is no significant difference in nuclear staining. Sometimes, cells with multiple nuclei or darkly stained nuclei or irregular stellate nuclei can be seen. Connective tissue proliferates around the tumor cell group, and the outermost layer is arranged in a palisade-like plug-like cell. Many immature fibroblasts and mature fibroblasts are often seen mixed around the tumor tissue. The stroma of basal cell carcinoma contains mucin, and when the slices are made, the stroma shrinks, causing the stroma to separate from the edge of the tumor mass in a fissure-like manner, which is of certain significance for the diagnosis of this disease. In histopathology, basal cell carcinoma can be divided into two major categories: differentiated and undifferentiated. The undifferentiated type can be manifested as a solid type, a pigmented type, a fibrotic type, or a hard plaque-like, superficial type. Solid type can be seen with different amounts and shapes of tumor masses buried in the dermis; pigmented type has more melanin between tumor cells; fibrotic or sclerotic type has significant connective tissue hyperplasia, connective tissue wraps around tumor cell groups in bundles; superficial type has more short bud-shaped tumor cell groups under the epidermis. Differentiated type can show keratinizing basal cell carcinoma that differentiates into hair structure, cystic basal cell carcinoma that differentiates into sebaceous glands, glandular basal cell carcinoma that differentiates into apocrine glands, etc.

Basal cell carcinoma almost always spreads by direct invasion; metastasis may occur, but this is extremely rare.

2. Squamous cell carcinoma Squamous cell carcinoma often presents as a subcutaneous nodule with a central ulcer, but can also present as a completely flat, scaly lesion. The common sites and incidence rates of squamous cell carcinoma are: head and neck 65%, upper limbs 25%, lower limbs 5%, and trunk 5%.

Microscopic observation: Cancer cells invade the dermis in clusters or cords, with varying numbers of normal and atypical incompletely differentiated squamous cells and dyskeratinized cells. The more atypical squamous cells there are, the higher the malignancy, which is manifested by unequal cell sizes, atypical nuclear divisions, dark staining, basophilic cytoplasm, and no intercellular bridges. The more differentiated the keratinized squamous cells are, the closer they are to the center, the more keratinized they are, and the center can be completely keratinized. Squamous cell carcinoma can be divided into four grades according to the proportion of atypical squamous cells in the tumor. Grade I: The tumor tissue does not exceed the level of sweat glands, there are less than 25% atypical squamous cells, there are many keratinized beads, and there is an obvious inflammatory reaction in the dermis; Grade II: The boundaries of the cancer cell cluster are unclear, atypical squamous cells account for about 25%-50%, there are only a few keratinized beads, the center of the keratinized beads is not fully keratinized, and the surrounding inflammatory reaction is mild; Grade M: Atypical squamous cells account for about 50%-75%, most of them are not keratinized, there are no keratinized beads, and the surrounding inflammatory reaction is not significant; Grade IV: Atypical squamous cells account for more than 75%, there are many nuclear division phases, no intercellular bridges, and no keratinization. The cancer cells are small and spindle-shaped, with elongated nuclei and dark staining, accompanied by necrosis and pseudoglandular structures. A few squamous cancer cells and keratinized cells can be used as a basis for diagnosis.