This video presents a detailed microscopic analysis of a dermatofibroma (DF) with atypical features, specifically identifying it as a Lipidized Dermatofibroma (colloquially termed "ankle-type"). The review highlights classic low-power DF characteristics, including prominent epidermal hyperplasia (acanthosis) and flattened rete ridges ("tables and chairs" sign), alongside striking collagen trapping. The lipidized variant is confirmed by the presence of abundant foamy/xanthoma-like cells and surrounding hyalinized, sclerotic collagen rings. The pathologist confirms that despite the large, pleomorphic cells and scattered mitoses, these findings are acceptable within the spectrum of DF. An incidental finding is the deep extension of the lesion into the underlying fascia and the inclusion of black tattoo pigment, indicating the DF developed within a tattooed area.
Dermatopathology Case Review: Lipidized Dermatofibroma (Ankle-Type)
0:07 Initial Diagnosis & Low Power Features: The lesion is identified as a typical Dermatofibroma (DF). At low power (0:17), the epidermis exhibits marked hyperplasia (acanthosis) and elongated rete ridges, which are often flattened at the base, referred to as the "tables and chairs" pattern (0:30).
1:25 Classic DF Trapping: A key feature is the striking collagen trapping (sclerosis), where background dermal collagen is squished and incorporated by the DF cells.
1:36 Variant Identification: The lesion exhibits features of a variant: dense, hyalinized sclerotic collagen forms arcs and rings around individual cells (2:02).
1:50 Lipidized Cells: Many cells possess abundant foamy cytoplasm, giving them a xanthoma-like appearance (1:55). This combination leads to the specific diagnosis of Lipidized Dermatofibroma.
2:30 Anatomical Correlation: Lipidized DFs are often referred to as "ankle-type" as they commonly arise on the lower leg near the ankle.
2:51 Cellular Atypia is Acceptable: The pathologist notes that DFs can tolerate significant cellular "weirdness," including large, plump cells, pleomorphism, and scattered mitoses, without raising concerns for malignancy.
3:36 Incidental Finding (Tattoo): Black, exogenous tattoo pigment is observed scattered throughout the dermis, confirming the lesion developed within a tattooed area.
4:32 Deep Extension: The DF is noted for its deep penetration, reaching the underlying fascia. Fascia is recognizable by the characteristic "Ramen Noodle sign," which describes the wavy, dense regular connective tissue.