Inverted Follicular Keratosis in Young Adult: A Rare Entity in the Differential Diagnosis of Skin Tumors

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Introduction: Inverted follicular keratosis (IFK) is a rare benign tumor arising from the follicular infundibulum, typically presenting as a solitary lesion on the head and neck of older adults. The actual incidence of inverted follicular keratosis is likely underreported due to frequent misdiagnosis as more common cutaneous lesions, including seborrheic keratosis, verruca vulgaris, or pyogenic granuloma. Case Presentation: We reported a rare case of IFK in a 26-year-old male with a solitary, asymptomatic, pedunculated lesion on the scalp. The patient presented with a 0.7 cm-sized lesion demonstrating intermittent bleeding and slow growth over three years. The lesion was initially diagnosed clinically as a pyogenic granuloma, reflecting its solitary skin lesion and bleeding tendency. On dermoscopy, white structureless amorphous areas with amorphous central keratinous plugs and blood spots were seen. The diagnosis of inverted follicular keratosis was established following histopathological examination, which revealed characteristic features of IFK, including endophytic proliferation and squamous eddies. This case underscores the diagnostic complexity of IFK, which can mimic both benign and malignant cutaneous tumors. Conclusion: IFK, while rare in young patients, should remain a differential diagnosis for scalp lesions across all age groups. Recognition of its dermoscopic and histopathologic features is critical to avoid misclassification and to guide appropriate management. Histopathologic assessment remains essential for establishing a definitive diagnosis.

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