Cutaneous carcinoma with mixed histology.

It is accepted that different histologic subtypes of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) exist, and that these subtypes differ in their biologic aggressiveness. In this issue of the Journal, Cohen and Nelson make a convincing argument that mixed histology BCCs and SCCs could represent a cause of recurrence when only the more benign histologic component is biopsied, thus causing the physician to select a treatment modality that is not sufficient to remove the more aggressive histologic component of the tumor.

While the authors' cite studies which report the incidence of mixed histology BCC to be between 10.5% (1) and 25%, (2) one could argue that the true incidence of this phenomenon is even higher. In one study, 1,039 consecutive BCC specimens sent to an academic dermatopathology lab were thoroughly sectioned, and 39% revealed more than one histologic subtype. (3) In another study, 129 consecutive BCCs treated with Mohs micrographic surgery were thoroughly sectioned, and 40% of these revealed more than one histologic subtype. (4) Mixed histology BCC is undeniably prevalent.

Since nonmelanoma skin cancer is the most common cancer in the United States (in 2005, the number of BCC and SCC alone will equal the number of all other cancers combined), the above is worth noting, as almost every physician will encounter it and have to make treatment decisions regarding it. We suggest the following to assist in treatment decisions: request the dermatopathologist to include the tumor's histologic subtype on the pathology report, perform clinicopathologic correlation, and select the appropriate treatment modality.

It is surprising that while dermatopathologists know that biologic behavior of nonmelanoma skin cancer is directly related to their histologic subtype, a minority of them actually report the subtype on their pathology reports. Physicians should have this information available when making decisions regarding treatment and should request their dermatopathologist to routinely include this in their reports.

One should certainly always perform clinicopathologic correlation with biopsies. If the pathology report indicates a less aggressive histology, but the tumor in question is clinically worrisome (large size, indurated) or if the clinical appearance of the tumor does not match the typical appearance of the reported histologic subtype, multiple histologies should be considered. In this case, it is most prudent to select the most effective treatment available.

Skin cancer is most easily and effectively treated when it is primary and not recurrent. As such, selecting the proper initial treatment is critical. Currently, Mohs micrographic surgery is recognized as the gold standard for treatment of nonmelanoma skin cancer. It is cost effective compared to excision, even more economical than excision with frozen sections, and delivers a higher cure rate. (5,6) Physicians and other health care providers should keep in mind that up to 40% of BCCs may be of mixed histology and should err on the conservative side when selecting treatment, especially when the cancer is located on a functionally (eyelid, lip, ear) or cosmetically (facial) sensitive area.

References

1. Swetter SM, Yaghmai D, Egbert BM. Infiltrative basal cell carcinoma occurringin sites of biopsy-proven nodular basal cell carcinoma. J Cutan Pathol 1998;25:420-425.

2. Freeman RG, Duncan WC. Recurrent skin cancer. Arch Dermatol 1973;107:395-399.

3. Sexton M, Jones DB, Maloney ME. Histologic pattern analysis of basal cell carcinoma. J Am Acad Dermatol 1990;23:1118-1126.

4. Jones MS, Maloney ME, Billingsley EM. The heterogeneous nature of in vivo basal cell carcinoma. Dermatol Surg 1998;24:881-884.

5. Cook J, Zitelli JA. Mohs micrographic surgery: A cost analysis. J Am Acad Dermatol 1998;39:698-703.

6. Bialy TL, Whalen J, Veledar E, et al. Mohs micrographic surgery versus traditional surgical excision. Arch Dermatol 2004;140:736-742.

Conway C. Huang, MD

From the University of Alabama at Birmingham, Birmingham, AL.

Reprint requests to Dr. Conway C. Huang, The University of Alabama at Birmingham, EFH 414, 1530 3rd Avenue South, Birmingham, AL 35294-0009. Email: [e-mail]

Accepted May 12, 2005.