Which histologic findings are characteristic of basal cell carcinoma (BCC)?

Updated: Mar 02, 2020
  • Author: Robert S Bader, MD; Chief Editor: William D James, MD  more...
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Answer

Several histologic types of BCC exist. Distinctions are important because clinical detection of tumor margins is more difficult with certain histologic types. [62] Usually, BCCs are well differentiated and cells appear histologically similar to basal cells of the epidermis.

Tumor cells of nodular BCC, sometimes called basalioma cells, typically have large, hyperchromatic, oval nuclei and little cytoplasm. Cells appear uniform, and if present, mitotic figures are usually few. The nuclei resemble that of the basal cells of the epidermis, although they have a larger nuclear-to-cytoplasmic ratio and lack intercellular bridges. A mitotic figure is very rarely observed. Nodular tumor aggregates may be of varying sizes, but tumor cells tend to align more densely in a palisade pattern at the periphery of these nests (see the image below).

Nodular basal cell carcinoma. Nodular aggregates o Nodular basal cell carcinoma. Nodular aggregates of basalioma cells are present in the dermis and exhibit peripheral palisading and retraction artifact. Melanin is also present within the tumor and in the surrounding stroma, as seen in pigmented basal cell carcinoma.

Cleft formation, known as retraction artifact, commonly occurs between BCC nests and stroma because of shrinkage of mucin during tissue fixation and staining. Some lobules may have areas of pseudoglandular change, and this is the predominant change in adenoid BCC. In other instances, large tumor lobules may degenerate centrally, forming pseudocystic spaces filled with mucinous debris. These changes are seen in the nodulocystic variant of BCC.

Early lesions usually have some connection to the overlying epidermis, but such contiguity may be difficult to appreciate in more advanced lesions. Increased mucin is often present in the surrounding dermal stroma.

A histopathologic examination of paraffin-embedded sections of BCC usually reveals solid cellular strands, collections of cells with dark-staining nuclei and scant cytoplasm.

The peripheral cell mass is in a palisade arrangement that resembles the basal layer of the epidermis, sometimes with pseudocystic aspects, and with a variable number of mitoses.

The connective tissue stroma surrounding the tumor islands is arranged in parallel bundles and often shows young fibroblasts immediately adjacent to the tumor. The specific histologic pattern of each type of BCC varies in terms of desmoplastic reaction of the morpheaform type and in the stromal islands separated by basal cells strands of the fibroepithelial type. Artificial retraction of the stroma from the tumor islands is frequently observed histologically. Additionally, the stroma is often mucinous. Cells from recurrent BCC often show squamous aspects.

Histologically, BCC is divided into 2 categories: undifferentiated and differentiated. When there is little or no differentiation, it is referred to as solid BCC and includes pigmented BCC, superficial BCC, sclerosing BCC, and infiltrative BCC (a histologic subtype).

Differentiated BCC often has slight differentiation toward cutaneous appendages, including hair (keratotic BCC), sebaceous glands (BCC with sebaceous differentiation), or tubular glands (adenoid BCC). Noduloulcerative (nodular) BCC is usually differentiated. See the images below.

Histologic pattern of a well-differentiated basal Histologic pattern of a well-differentiated basal cell carcinoma (original magnification X140). Courtesy of Prof Pantaleo Bufo, University of Foggia, Italy.

When the presence of a dense inflammatory infiltrate obscures the histologic margins of BCC, immunohistochemical stains for cytokeratins can help to identify tumor cells. These stains can be used with fixed or frozen tissue. Such staining with frozen tissue can take as little as 19 minutes, making it practical for use with Mohs micrographic surgery or with standard excision with frozen section margin control. [63]


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