Basal cell carcinoma pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Shivali Marketkar, M.B.B.S. [2]

Overview

Basal cell carcinomas develop in the basal cell layer of the skin. Cumulative DNA damage caused by chronic sunlight exposure results in DNA mutations that predispose to the development of basal cell carcinoma. On gross pathology, basal cell carcinoma lesions may demonstrate pearly pink nodules with telangiectasias, rolled borders, and central crusting with or without an ulcerating lesion (rodent ulcer). On microscopic analysis, peripheral palisading nuclei are characteristic.

Pathophysiology

Genetics

A number of aberrations involving the sonic hedgehog signaling pathway(SHH) are noted^[1]^[2]^[3]
This pathway is vital for the regulation of cell growth, and differentiation and loss of inhibition of this pathway is associated with development of basal cell cancer
The majority of mutations in sporadic basal cell carcinoma and basal cell nevus syndrome(BCNS) patients occur in PTCH1 gene, a protein that inhibits smoothened gene(SMO)
The second most common mutation in sporadic basal cell carcinoma and basal cell nevus syndrome(BCNS) patients are gain-of-function mutations of the smoothened gene(SMO)
Loss of PTCH1 results in the failure of Smoothened inhibition, subsequently leading to increases in GLI1 levels, changes in transcription, and subsequent tumorigenesis
Gain-of-function smoothened(SMO) mutations also leads to increased GLI1 levels and tumorigenesis

Loss of PTCH1

Gain of function SMO

Lack of SMO inhibition

Activation of
SMO-GLI signaling

↑GLI1 levels

Changes in transcription

Tumorigenesis

Enviromental Exposure

Basal cell carcinomas develop in the basal cell layer of the skin
Cumulative DNA damage caused by chronic sunlight exposure results in DNA mutations that predispose to the development of basal cell carcinoma
While DNA repair eliminates most UV-induced damage, not all cross-links are excised, which eventually results in mutations
Apart from the mutagenesis, sunlight depresses the local immune system, possibly decreasing immune surveillance for new tumor cells

Pathology

Basal cell carcinoma pathological features mainly depend upon the subtype. The following table summarizes them:^[4]^[5]

Subtypes of BCC	Gross features		Microscopic features
Subtypes of BCC	Findings	Images	Findings	Images
Nodular	Shiny, pearly papule or nodule with a smooth surface Rolled borders and telangiectasias Mostly seen on the head and neck	M. Sand, D. Sand, C. Thrandorf, V. Paech, P. Altmeyer, F. G. Bechara [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons	Discrete nests of malignant basaloid cells in the dermis Peripheral palisading Mucoid stroma containing plump spindle cells	No machine-readable author provided. KGH assumed (based on copyright claims). [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons,https://upload.wikimedia.org/wikipedia/commons/b/b6/Basal_cell_carcinoma_histopathology_%283%29.jpg
Superficial	Well-circumscribed Erythematous thin plaque or patch with scale Central clearing and thin rolled borders Most common on the trunk	Kelly Nelson (Photographer) [Public domain], via Wikimedia Commons,https://upload.wikimedia.org/wikipedia/commons/3/32/Basal_cell_carcinoma%2C_superficial.jpg	Multiple lobular foci of basaloid palisading keratinocyte tumors These are usually attached superficially to the epidermis with a myxoid stroma and band-like lichenoid infiltrate	machine-readable author provided. KGH assumed (based on copyright claims). [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
Infundibulocystic	Well-circumscribed pearly papule Most common on the head and neck region		Well-circumscribed Anastomosing strands of basaloid cells and scattered infundibulum-like cystic structures
Fibroepithelial	Skin-colored/erythematous Sessile plaque/pedunculated papulonodule They have a predilection for trunk region		Multiple collections of delicate strands of epidermal basaloid keratinocytes These are usually arranged in a reticular pattern within a spindle cell stroma
Morpheaform	Infiltrated plaque with poorly defined borders and shiny surface Most common on head and neck region	Dermatology Centre, Salford Royal Hospital, NHS Foundation Trust, Stott Lane, Salford M6 8HD, UK.	Thin cords of basaloid cells surrounded by a sclerotic collagenous stroma Absent peripheral palisading and stromal cleft formation Positive staining of tumor stroma with smooth muscle alpha-actin	Department of Pathology, Columbia University Medical Center, New York, USA
Infiltrative	Poorly defined Indurated, flat or depressed plaque with white, yellow, or pale pink color They may have overlying crusts, erosions, ulcerations, or papules	Kelly Nelson (Photographer) [Public domain], via Wikimedia Commons,https://upload.wikimedia.org/wikipedia/commons/9/9b/Basal_cell_carcinoma_%281%29.jpg,	Thin cords with angulated ends of few basaloid keratinocytes Usually embedded in a classic mucinous/myxoid stroma
Micronodular	Erythematous macule or thin papule/plaque		Multiple small aggregates of basaloid cells within the dermis, with subtle peripheral palisading and retraction artifact
Basosquamous	Majority found on the head and neck		Well-defined nodular or superficial BCC component overlying an invasive front showing basal cell carcinoma and squamous cell carcinoma histologic feature

Video

References

↑ Mohan SV, Chang AL (2014). "Advanced Basal Cell Carcinoma: Epidemiology and Therapeutic Innovations". Curr Dermatol Rep. 3: 40–45. doi:10.1007/s13671-014-0069-y. PMC 3931971. PMID 24587976.
↑ Pellegrini C, Maturo MG, Di Nardo L, Ciciarelli V, Gutiérrez García-Rodrigo C, Fargnoli MC (November 2017). "Understanding the Molecular Genetics of Basal Cell Carcinoma". Int J Mol Sci. 18 (11). doi:10.3390/ijms18112485. PMC 5713451. PMID 29165358.
↑ Yunoki T, Tabuchi Y, Hirano T, Miwa S, Imura J, Hayashi A (November 2018). "Gene networks in basal cell carcinoma of the eyelid, analyzed using gene expression profiling". Oncol Lett. 16 (5): 6729–6734. doi:10.3892/ol.2018.9484. PMC 6202553. PMID 30405815.
↑ Cameron, Michael C.; Lee, Erica; Hibler, Brian P.; Barker, Christopher A.; Mori, Shoko; Cordova, Miguel; Nehal, Kishwer S.; Rossi, Anthony M. (2019). "Basal cell carcinoma". Journal of the American Academy of Dermatology. 80 (2): 303–317. doi:10.1016/j.jaad.2018.03.060. ISSN 0190-9622.
↑ Sehgal VN, Chatterjee K, Pandhi D, Khurana A (2014). "Basal cell carcinoma: pathophysiology". Skinmed. 12 (3): 176–81. PMID 25134314.

Template:WikiDoc Sources

[pmid24587976-1] Mohan SV, Chang AL (2014). "Advanced Basal Cell Carcinoma: Epidemiology and Therapeutic Innovations". Curr Dermatol Rep. 3: 40–45. doi:10.1007/s13671-014-0069-y. PMC 3931971. PMID 24587976.

[pmid29165358-2] Pellegrini C, Maturo MG, Di Nardo L, Ciciarelli V, Gutiérrez García-Rodrigo C, Fargnoli MC (November 2017). "Understanding the Molecular Genetics of Basal Cell Carcinoma". Int J Mol Sci. 18 (11). doi:10.3390/ijms18112485. PMC 5713451. PMID 29165358.

[pmid30405815-3] Yunoki T, Tabuchi Y, Hirano T, Miwa S, Imura J, Hayashi A (November 2018). "Gene networks in basal cell carcinoma of the eyelid, analyzed using gene expression profiling". Oncol Lett. 16 (5): 6729–6734. doi:10.3892/ol.2018.9484. PMC 6202553. PMID 30405815.

[CameronLee2019-4] Cameron, Michael C.; Lee, Erica; Hibler, Brian P.; Barker, Christopher A.; Mori, Shoko; Cordova, Miguel; Nehal, Kishwer S.; Rossi, Anthony M. (2019). "Basal cell carcinoma". Journal of the American Academy of Dermatology. 80 (2): 303–317. doi:10.1016/j.jaad.2018.03.060. ISSN 0190-9622.

[pmid25134314-5] Sehgal VN, Chatterjee K, Pandhi D, Khurana A (2014). "Basal cell carcinoma: pathophysiology". Skinmed. 12 (3): 176–81. PMID 25134314.

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