Clear Cell Hidradenoma-Basal Cell Carcinoma Collision

Area of Science:

• Dermatopathology
• Oncology

Background:

• Collision tumors, where two distinct neoplasms arise in proximity, present diagnostic complexities.
• Basal cell carcinoma (BCC) is common, while clear cell hidradenoma (CCH) is a rare benign adnexal neoplasm.

Observation:

• A 91-year-old male presented with a left temporal tumor clinically suspected as BCC.
• Histopathology revealed a central solid-cystic tumor with three cell types and sclerotic stroma, adjacent to a peripheral tumor with nests and cellular stroma.
• Immunohistochemistry confirmed distinct neoplastic entities.

Findings:

• The histopathological and immunohistochemical findings supported a diagnosis of a collision tumor.
• The specific diagnosis was clear cell hidradenoma co-occurring with basal cell carcinoma.
• A sharp demarcation without transitional zones was noted between the two distinct tumors.

Implications:

• This case represents the first documented instance of a clear cell hidradenoma-basal cell carcinoma collision.
• Accurate diagnosis requires meticulous histopathological examination and immunohistochemistry.
• Understanding such rare associations is crucial for effective clinical management and patient prognosis.