Primitive follicular induction in molluscum contagiosum.
BACKGROUND
Molluscum contagiosum (MC) is the commonest human poxvirus infection. Follicular induction has rarely been observed in the epidermis surrounding lesions of MC. A virus-induced localized proliferation of germinative/stem cells of the folliculosebaceous-apocrine unit has been suggested as the underlying cause, however few reports of this peculiar phenomenon exist in the literature and the mechanisms involved in this proliferation require further study.


METHODS
We prospectively collected MC cases showing multifocal areas of primitive follicular induction involving the adjacent undersurface epidermis. Immunohistochemical expression of BerEP4, PHLDA1 and cytokeratin 20 (CK20) was evaluated in the basaloid germs surrounding the lesions. For PHLDA1, we used epidermal melanocytes as a positive internal control. For BerEP4, we employed a basal cell carcinoma (BCC) and for CK20, colon as positive external controls. An incubation without the primary antibody functioned as an external negative control.


RESULTS
All the cases studied showed an intense positive staining of the basaloid buds with BerEP4 and weaker stain for PHLDA1. CK20 showed the presence of scattered Merkel cells within the induced epidermal basaloid proliferations favoring their reactive origin.


CONCLUSIONS
The pathogenetic mechanisms behind the development of these microscopic features and the link between follicular induction and poxvirus infection are explored. Awareness of this unusual phenomenon by dermatopathologists will be helpful in avoiding a misdiagnosis of a superficial BCC in such cases.


CONCLUSIONS
BerEP4 and PHLDA1 were consistently expressed in the areas of primitive follicular induction surrounding lesions of MC. CK 20 stained the Merkel cells present in the basaloid buds. All these findings support the reactive origin of this phenomenon, which we believe is most probably viral-induced.
Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Madrid, Spain.
Ana María
AM
Molina-Ruiz
Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Madrid, Spain.
Claudia
C
Bernárdez
Department of Dermatology, Fundación Jiménez Díaz, Universidad Autónoma, Madrid, Spain.
Luis
L
Requena
Dermatopathology laboratory, Dermatophathologisches Gemeinschaftslabor, Friedrichshafen, Germany.
Leo
L
Schärer
D014408:Biomarkers, Tumor / Q000378:metabolism; D002280:Basal Cell Carcinoma / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D018859:Hair Follicle / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D006801:Humans; D007150:Immunohistochemistry; D053554:Keratin-20 / Q000378:metabolism; D018862:Merkel Cells / Q000378:metabolism / Q000473:pathology / Q000821:virology; D018169:Molluscipoxvirus / Q000302:isolation & purification; D008976:Molluscum Contagiosum / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D011213:Poxviridae Infections / Q000378:metabolism / Q000473:pathology / Q000821:virology; D011446:Prospective Studies; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology; D014157:Transcription Factors / Q000378:metabolism; D000951:Antigens, Neoplasm
D014408:Biomarkers, Tumor; D053554:Keratin-20; D014157:Transcription Factors; C491923:PHLDA1 protein, human; C115012:human epithelial antigen-125; D000951:Antigens, Neoplasm
Merkel cells; basal cell carcinoma; follicular induction; molluscum contagiosum