CRTC1::MAML2-Positive Hidradenoma With Sebaceous Differentiation

Area of Science:

• Dermatopathology
• Oncology
• Molecular Pathology

Background:

• Hidradenoma is a benign adnexal neoplasm with diverse cell morphologies.
• Sebocytes, or sebaceous cells, have not previously been reported in hidradenoma.
• Cutaneous adnexal tumors require precise classification for accurate diagnosis and treatment.

Observation:

• A 66-year-old male presented with a lip nodule containing a multinodular tumor.
• Histopathology revealed ductoglandular and basaloid cells with scattered sebocytes.
• Immunohistochemistry confirmed sebaceous differentiation (Adipophilin) and a CRTC1::MAML2 fusion via FISH and sequencing.

Findings:

• The tumor exhibited features of hidradenoma with distinct sebaceous differentiation.
• A CRTC1(e1)::MAML2(e2) gene fusion was identified, confirming the molecular basis.
• The presence of sebocytes in this hidradenoma case is a novel observation.

Implications:

• Hidradenoma should be considered in the differential diagnosis of cutaneous adnexal tumors with sebaceous features.
• This case expands the recognized cellular components of hidradenoma to include sebocytes.
• Understanding these rare variants aids in accurate histopathological diagnosis and patient management.