Abstract
Cutaneous collision tumors are a rare clinical phenomenon, involving diverse combinations of benign and malignant neoplasms, which have been reported in various contexts. Previous reports have documented the occurrence of atypical fibroxanthoma in combination with invasive melanoma, basal cell carcinoma, and mycosis fungoides. Remarkably, only one case of a collision tumor consisting of atypical fibroxanthoma and squamous cell carcinoma has been previously reported. In this account, we detail the second such case. A 66-year-old male patient presented with a distinctive nodule on his right helix. Histopathological examination of the skin lesion revealed moderately differentiated atypical keratinocytes invading the dermis, accompanied by acanthosis, hyperkeratosis, and parakeratosis. Additionally, a proliferation of spindle, oval, and round cells is also present in the dermis, exhibiting atypical nuclei, multinucleation, and occasional mitotic figures. Immunohistochemistry revealed that the spindle cells are positive for CD68 and CD10. Concurrently, the squamous cell carcinoma cells are positive for AE1/AE3, CK5/6, and CK903. The diagnosis of moderately differentiated squamous cell carcinoma in conjunction with atypical fibroxanthoma was rendered. In light of this diagnosis, we suggest that when a spindle cell lesion is observed in tandem with a dermatopathological malignancy, the differential diagnosis should include the possibility of a collision tumor with an atypical fibroxanthoma component. For the purpose of ensuring a precise diagnosis, it is of utmost importance for dermatopathologists to be alert to the potential occurrence of these rare collision tumors.