Melanoma associated with a dermatofibroma.

Area of Science:

• Dermatopathology
• Oncology
• Immunohistochemistry

Background:

• Dermatofibromas are common benign fibrohistiocytic neoplasms.
• Melanomas are potentially aggressive malignancies.
• Distinguishing between these two entities can be diagnostically challenging.

Observation:

• A 56-year-old female presented with a firm pink papule on her left thigh.
• Histopathology revealed atypical melanocytes with mitotic activity and pagetoid spread.
• A poorly demarcated collection of epithelioid and spindled cells with keloidal collagen was noted in the dermis.

Findings:

• Immunohistochemical staining confirmed invasive malignant melanoma (MART-1+, S-100+) co-occurring with a dermatofibroma (Factor XIIIa+).
• The study highlights a rare case of dual neoplasms.
• Histopathological and immunohistochemical analysis were key to the diagnosis.

Implications:

• This case underscores the importance of immunohistochemistry in differentiating melanocytic and histiocytic neoplasms.
• Accurate diagnosis is critical for appropriate patient management and prognosis.
• Understanding the coexistence of benign and malignant skin lesions is essential for dermatologists.