Metatypical Basal Cell Carcinoma

This needs to be differentiated from basal cell carcinoma with keratinization. Many basal cell carcinomas ulcerate; the resultant inflammation at the periphery induces reactive keritinization. The fibrous pattern can also be found in non-metatypical basal cell carcinomas. There, physical trauma, such as patient picking the lesion, may have been present overlying the basal cell carcinoma ulceration. Again, this is not equivalent to the more aggressive metatypical basosquamous cell carcinoma, but indeed represents variants of basal cell carcinoma behavior.

Often, the use of the term basosquamous cell carcinoma does not adequately describe the nature of the cutaneous cancer and thus requires further definition of the term. True metatypical basosquamous cell carcinomas must be treated as highly aggressive tumors with metastatic potential. As clinicians, we must rely on our pathology colleagues to make that differentiation, and we must question each diagnosis of basosquamous cell carcinoma.

This carcinoma behaved as a true metatypical BCCa with infiltrative features, deep aggressive fixation, and perineural involvement. There were clearly two cell types, basal cells and small spindle cells with desmoplastic reaction of the neuroendocrine component. The latter required immunohistochemistry for confirmation.

Many lesions with basal and squamous cell component are called metatypical basal cell carcinomas without being true metatypical cancers. This is particularly prevalent on a biopsy diagnosis where the full extent of the cancer cannot be visualized given the small size of biopsy specimen. Most of those cases show either reactive keratinization or inflammatory surface squamous metaplasia. This case is the classic metatypical BCCa with its aggressive behavior and two cell types throughout the tumor.