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Nevus sebaceus (NS) is a congenital hamartoma involving epidermis and adnexal structures [1]. Approximately 95% of cases occur on the head, face, or neck, presenting as yellowish alopecic patches at birth and occasionally developing secondary tumors [2, 3]. Here, we present a case of hair transplantation in NS followed by secondary tumors, maintaining the hair cycle for approximately 40 years. A 70-year-old woman presented with a red nodule and yellowish papules arising within a congenital alopecic plaque on her scalp (Figure 1a). At around age 30, she underwent autologous hair transplantation onto the lesion. Trichoscopy revealed numerous terminal hairs growing adjacent to the nodules (Figure 1b). The whole lesion was resected and reconstructed with a local rotation flap. Histopathologically, the yellowish papule showed proliferation of sebaceous lobules. The background lesion was consistent with NS based on sebaceous gland proliferation, apparent opening onto the epidermal surface, and seborrheic keratosis-like epidermal changes. The papule was diagnosed as sebaceous hyperplasia arising within NS (Figure 1c). The red nodule exhibited features of desmoplastic trichilemmoma, including clear cytoplasm, continuity with the epidermis, endophytic growth, and surrounding collagen proliferation (Figure 1d). The adjacent area showed tumor cell nests with peripheral palisading and hair germ-like structures without fissures or mucin deposition, suggestive of trichoblastoma (Figure 1e). Immunohistochemically, the red nodule was partially positive for CD34 (Figure 1f) and negative for EMA and Ber-EP4. According to these findings, we diagnosed desmoplastic trichilemmoma, trichoblastoma, and sebaceous hyperplasia arising from NS [4]. Both trichilemmoma and trichoblastoma were confined to and histologically continuous with NS, and no similar nodules were identified elsewhere on the scalp or face, supporting their secondary origin. Within the lesion, hair follicles extended into the subcutaneous tissue and showed well-formed bulbs, dermal papillae, and thick hair shafts with a distinct medulla, consistent with mature terminal follicles (Figure 1g). Unlike the immature and superficially located follicles typical of NS, these follicles exhibited normal architecture and were interpreted as transplanted hairs (Figure 1h). Terminal hairs were observed at the periphery of each tumor, suggesting that the secondary tumors developed after transplantation. These findings indicate that transplanted follicles in NS maintained long-term hair cycling. Lee et al. reported that hairlessness in NS might result from reduced expression of growth factors such as Wnt10b and Lef1, and increased expression of inhibitors, including DKK-1, FGF-5 [5]. They showed that NS sebocyte-conditioned medium reduced the viability of outer root sheath and dermal papilla cells, implicating altered bioactive factors in impaired terminal hair growth [5]. However, in our case, the transplanted hairs with retained mature follicles maintained hair cycling for decades. Hair follicle-containing transplantation introduces a fully formed epithelial-mesenchymal unit, and once engrafted and revascularized, follicle cycling may be governed largely by the intrinsic follicular niche, making it relatively resistant to inhibitory paracrine cues from NS sebocytes. This suggests that NS-related factors may impair hair morphogenesis but not the hair cycle. Importantly, secondary tumors developed decades after transplantation, indicating that hair transplantation does not eliminate the tumorigenic potential of NS. Complete excision is standard treatment for NS. Daisuke Tsuruta is an Editorial Board member of Journal of Dermatology and a coauthor of this article. To minimize bias, he was excluded from all editorial decision-making related to the acceptance of this article for publication. We have obtained the informed consent appropriately. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.