This video segment discusses the histopathological features of an "acquired digital fibrokeratoma," a benign, polypoid skin lesion resembling an acrochordon (skin tag) but characterized by thick, acral-type skin lining (acanthotic epidermis and thick orthokeratin). The underlying dermis exhibits a fibrotic appearance with vertical collagen bundles and bland fibroblasts/myofibroblasts, often with dilated vessels. The speaker highlights the significant overlap in appearance with angiofibromas and specifically the periungual fibroma (Koenen tumor) associated with tuberous sclerosis, while emphasizing that the acquired digital fibrokeratoma is not associated with that condition. Other differential diagnoses discussed include superficial acral fibromyxoma. The speaker notes that while most cases occur on digits, they can occasionally be found on the palms or soles (termed "acral fibrokertoma" in those instances).
Differential Diagnosis of a Skin Lesion: Acquired Digital Fibrokeratoma
00:00:15 Histological Findings: The lesion shows dense dermal collagen, an acral surface, and vertically oriented collagen bundles in the dermis along with Bland fibroblasts/myofibroblasts and dilated vessels.
00:00:40 Diagnosis: The lesion is identified as an acquired digital fibrokeratoma, described as a polypoid lesion shaped like a skin tag (acrochordon) but lined by thick acral skin (thick acanthotic epidermis and orthokeratin).
00:01:24 Overlap with Angiofibroma: The histology closely resembles an angiofibroma or fibrous papule, and the speaker places it on the angiofibroma spectrum.
00:01:39 Related Condition (Tuberous Sclerosis): The appearance is similar to a periungual fibroma (Koenen tumor) seen in tuberous sclerosis, but the acquired digital fibrokeratoma is not associated with that syndrome.
00:02:35 Koenen Tumors as a Late Sign: Koenen tumors are usually one of the last cutaneous signs of tuberous sclerosis to develop.
00:03:07 Benign Nature: Acquired digital fibrokeratomas are benign, typically occurring on the digits, but sometimes on the palm or sole (where the speaker suggests calling it an "acral fibrokertoma").
00:03:39 Differential Diagnoses: Main differentials include periungual fibroma and superficial acral fibromyxoma (or digital fibromyxoma), which may show myxoid change and be more cellular.
00:04:06 Related Tumors: Superficial acral fibromyxoma is suggested to be related to spindle cell lipomas.