It is currently believed that the epidermal sebaceous gland (SG) is maintained by unipotent stem cells that are replenished by multipotent stem cells in the hair follicle (HF) bulge. However, sebocytes can be induced by Myc activation in interfollicular epidermis (IFE), suggesting the existence of bipotential stem cells. We found that every SZ95 immortalised human sebocyte that underwent clonal growth in culture generated progeny that differentiated into both sebocytes and cells expressing involucrin and cornifin, markers of IFE and HF inner root sheath differentiation. The ability to generate involucrin positive cells was also observed in a new human sebocyte line, Seb-E6E7. SZ95 xenografts differentiated into SG and IFE but not HF. SZ95 cells that expressed involucrin had reduced Myc levels; however, this did not correlate with increased expression of the Myc repressor Blimp1, and Blimp1 expression did not distinguish cells undergoing SG, IFE or HF differentiation in vivo. Overexpression of Myc stimulated sebocyte differentiation, whereas overexpression of beta-catenin stimulated involucrin and cornifin expression. In transgenic mice simultaneous activation of Myc and beta-catenin revealed mutual antagonism: Myc blocked ectopic HF formation and beta-catenin reduced SG differentiation. Overexpression of the Myc target gene Indian Hedgehog did not promote sebocyte differentiation in culture and cyclopamine treatment, while reducing proliferation, did not block Myc induced sebocyte differentiation in vivo. Our studies provide evidence for a bipotential epidermal stem cell population in an in vitro model of human epidermal lineage selection, and highlight the importance of Myc as a regulator of sebocyte differentiation.

Ectopic modified sebaceous glands in human penis.Int J Surg Pathol. 2006 Oct;14(4):355-6.

The balanopreputial sulcus is believed to be the most frequent site of the so-called Tyson's glands. The intriguing feature of these anatomical structures is their mere existence, which has been doubted. Herein, the authors present a case of a 24-year-old man who underwent surgical treatment of his phimosis. On microscopic examination of the specimen, glands with morphological features similar to those described by Tyson were noted.

Heterotopic sebaceous glands in the esophagus: histopathological and immunohistochemical study of a resected esophagus.Pathol Int. 1999 Apr;49(4):364-8.

A resected esophagus with numerous heterotopic sebaceous glands was examined in an attempt to determine whether esophageal heterotopic sebaceous glands are the result of a metaplastic process or a congenital anomaly. The present case concerns a 79-year-old Japanese man with numerous esophageal heterotopic sebaceous glands accompanied by superficial esophageal cancer. The resected esophagus possessed numerous heterotopic sebaceous glands, which could be seen clearly as slightly elevated, yellowish lesions. Histological examination of these glands, all of which were located in the lamina propria, revealed lobules of cells that showed characteristic sebaceous differentiation. Bulbous nests of proliferating basal cells showing sebaceous differentiation were occasionally observed in the esophageal epithelium. Of the antibodies against six different keratins used, only anti-keratin 14 labeled both the heterotopic sebaceous glands and the bulbous nests. Acquired metaplastic change of the esophageal epithelium is probably the pathogenetic mechanism involved in these unusual lesions.

Areolar sebaceous hyperplasia with a Fordyce's spot-like lesion.J Dermatol. 1994 Jul;21(7):524-6.

Fordyce's spot-like lesions were observed in both areolae of a 43-year-old female. The histology of the lesions showed sebaceous hyperplasia.