Abstract

Basomelanocytic tumors are rare biphasic neoplasms composed of a melanocytic proliferation closely associated with, if not wholly contained within, basal cell carcinoma. The melanocytic component may be obscured by carcinoma on routine histopathologic examination, posing a diagnostic challenge that can have profound clinical impact given the possibility for metastatic spread. Histopathologic features to suggest malignant potential and, in cases of suspected melanoma, the prognostic utility of microstaging parameters remain uncertain. Here, we contribute two additional cases of basomelanocytic tumor with melanocytic components compatible with malignant melanoma. Dermatology was consulted to biopsy a nasal skin lesion on a 71 year old man with metastatic melanoma of unknown primary. There was a pearly pink plaque and adjacent pigmented nodule that, according to the patient, was a recurrence of a lesion previously treated by electrodessication and curettage. While the plaque showed conventional basal cell carcinoma, the nodule was composed of pigmented basal cell carcinoma within which were clusters of severely atypical melanocytes. The second case is of a 67 year old male who presented with a pearly plaque on the left neck that was close to the site of a previous melanoma excision by patient report. Biopsy revealed a heavily pigmented basal cell carcinoma with melanoma in situ focally present in the epidermis. Clusters of severely atypical melanocytes were present within nests of basal cell carcinoma that extended to the deep dermis. Wide excision showed residual tumor with similar features, except invasive melanoma was present within the reticular dermis outside of carcinoma. A left neck lymph node dissection was negative for metastatic disease. These two cases with clinical and histopathologic features compatible with melanoma raise the possibility of role for local skin cancer recurrence in the formation of some basomelanocytic tumors.

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