Basosquamous carcinoma of skin
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Synopsis

Basosquamous carcinoma (BSC) is a rare skin cancer that comprises less than 2% of nonmelanoma skin malignancies and presents frequently in patients aged 70 and older. Risk factors include ultraviolet (UV) exposure, tobacco use, xeroderma pigmentosum, immunosuppression, and Fitzpatrick skin types I-II. BSC has histopathologic features of squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). Although its pathogenesis is not fully understood, recent literature suggests that BSC is a type of BCC that has genetically undergone partial squamatization. Compared to SCCs and BCCs, BSCs are more aggressive and associated with more significant rates of recurrence (up to 45%) and metastasis (approximately 5%-10%), with the most common sites being lymph nodes and lungs.
Codes
ICD10CM:
C44.90 – Unspecified malignant neoplasm of skin, unspecified
SNOMEDCT:
254702000 – Basosquamous carcinoma of skin
C44.90 – Unspecified malignant neoplasm of skin, unspecified
SNOMEDCT:
254702000 – Basosquamous carcinoma of skin
Look For
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
- SCC – Presents as a hyperkeratotic papule or nodule, often with overlying scale. Ulceration may also be seen.
- BCC – Presentation is variable depending on the subtype. The nodular variant presents as a pearly telangiectatic nodule with rolled edges.
- Keratoacanthoma
- Sebaceous hyperplasia
- Molluscum contagiosum
- SCC in situ (Bowen disease)
- Trichoblastoma
- Trichoepithelioma
- Intradermal nevus
- Lichen planus-like keratosis
- Atypical fibroxanthoma
- Adenoid cystic carcinoma (see adenoid cystic carcinoma of ear)
- Merkel cell carcinoma
- Eccrine carcinoma
- Microcystic adnexal carcinoma
Best Tests
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Management Pearls
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Therapy
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References
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Last Reviewed:01/02/2023
Last Updated:02/07/2023
Last Updated:02/07/2023