Squamous cell carcinoma pathology

Spindle cell SCC

Not uncommon. It occurs in sun exposed areas and is associated with a good prognosis. Less commonly spindle cell SCC occurs after ionizing radiation, trauma or sometimes in organ transplant patients. These have worse prognosis (figures 11,12).

Figure 11

Figure 12

Clear cell SCC

Clear cells containing glycogen are seen in a variable proportions of this tumour. A signet ring SCC is a variant demonstrating clear cells with glycogen compressing and displacing the nucleus laterally (figures 13, 14).

Figure 13

Figure 14

Desmoplastic SCC

High risk of local recurrence and metastases. Nests and strands surrounded by an intense desmoplastic stromal reaction. Cellular pleomorphism and perineural invasion are frequent features. By definition 1/3 of the tumour should be desmoplastic (figures 15, 16).

Figure 15

Figure 15

Verrucous carcinoma

High recurrence rate but metastases are rare (except anogenital lesions, which may be related to HPV). Exo-endophytic lesions with bulbous profile and pushing margins. Pleomorphism and mitotic activity is usually minimal and peripheral(figures 17, 18; 18 (B) shows HPV effect).

Figure 17

Figure 18

Follicular SCC

Frequently found on the head and neck. Develop in the upper part of the hair follicles (figures 19, 20, 21).

Figure 19

Figure 20

Figure 21

Keratoacanthoma-like SCC

Some consider keratoacanthoma (KA) within the spectrum of well differentiated SCC. This subtype is somewhat controversial (figures 22, 23, 24).

Figure 22

Figure 23

Figure 24

Acantholytic SCC

Uncommon variant (2-4%). Central acantholysis leading to an impression of gland formation (figures 25, 26).

Figure 25

Figure 26

Pseudovascular SCC

Tends to affect men again in sun exposed sites. Recurrence and metastatic rate is high as is mortality. Rare as a primary skin SCC (figure 27).

Figure 27

Adenosquamous carcinoma/ mucoepidermoid carcinoma of the skin

Cutaneous SCC with glandular differentiation is rare. The head and neck are almost exclusively affected. Glandular differentiation may be sparse (figures 28, 29).

Figure 28

Figure 28

Metaplastic SCC (carcinosarcoma, carcinoma with heterologous differentiation)

Exceedingly rare. This is a biphasic tumour with malignant epithelial (SCC, BCC or adnexal malignancy) and mesenchymal components (figures 30, 31).

Figure 30

Figure 31

Inflammatory SCC

Dense lymphocytic stromal infiltrate surrounding poorly differentiated squamous nests. This SCC has high metastatic potential (figures 32, 33).

Figure 32

Figure 33

Basaloid SCC

Found in the oropharynx and anogenital region. High association with HPV infection in anogenital lesions. Small basaloid cells with a high mitotic rate (figures 34, 35)

Figure 34

Figure 35

Infiltrative SCC

Small nests and strands or single cells infiltrating a dermis which is fibrous and/or mucinous (figure 36).

Figure 36

Pigmented SCC

Melanin is found in epithelial tumour cells as well as in macrophages and dendritic melanocytes. This variant must be distinguished from the squamomelanocytic tumour, in which both a squamous cell carcinoma and melanoma components may occur.

Pseudohyperplastic SCC

Non-verruciform lesion that occurs on the penis. Associated with lichen sclerosus. Well-differentiated keratinizing nests of squamous cells with minimal atypia surrounded by a reactive fibrous stroma.