Track

Case Reports

Abstract

Merkel cell carcinoma is a rare and aggressive neuroendocrine skin cancer, often associated with a poor prognosis due to its propensity for rapid growth, local recurrence, and metastasis. The combination of Merkel cell carcinoma with other skin malignancies such as squamous cell carcinoma has been well documented. However, the collision of the neuroendocrine tumor with basal cell carcinoma is exceedingly rare. We report a 69-year-old male who presented with a 1.8 cm red, crusted, exophytic plaque of the right postauricular area. Histologic evaluation revealed nodular basal cell carcinoma with an additional morphologically and immunophenotypically distinct basaloid component. This population had a higher nuclear to cytoplasmic ratio, neuroendocrine chromatin pattern, nuclear molding and stained positive for chromogranin, synaptophysin and CK20. Overall, the histopathology was most compatible with a combined/collision tumor involving primary cutaneous Merkel cell carcinoma and basal cell carcinoma. Our case suggests that this unusual morphologic presentation of Merkel cell carcinoma can be overlooked and should be recognized when evaluating biopsies demonstrating basal cell carcinoma. Our case emphasizes the importance of considering a collision tumor of Merkel cell carcinoma and basal cell carcinoma over simple neuroendocrine differentiation or Merkel cell hyperplasia in basal cell carcinoma and the use of select immunohistochemical stains in such cases for an early and accurate diagnosis.