Pleomorphic dermal sarcoma
PDS; superficial undifferentiated pleomorphic sarcoma (cutaneous); the higher-grade cousin of AFX
Pleomorphic dermal sarcoma is a high-grade, undifferentiated pleomorphic sarcoma of the skin defined by its histological identity to atypical fibroxanthoma (AFX) but with at least one adverse feature: subcutaneous invasion beyond the superficial fascia, tumour necrosis, or lymphovascular / perineural invasion. While AFX is essentially a benign tumour of the elderly head, PDS has a 10–30% rate of local recurrence and a 10–20% rate of metastasis (skin, parotid, lung) and demands more aggressive management. Tumour shares the AFX UV-driven mutational landscape (TP53, telomerase reverse transcriptase promoter, NOTCH).
Distinction from AFX
PDS shares histological features with AFX (pleomorphic atypical spindled and epithelioid cells, S100/MelanA/cytokeratin negative) but is defined by at least one of:
- Tumour invasion beyond the superficial subcutaneous fascia.
- Tumour necrosis.
- Lymphovascular invasion.
- Perineural invasion.
An adequate deep biopsy (excisional rather than superficial shave) is therefore essential — superficial sampling cannot reliably distinguish AFX from PDS, and many "AFX" diagnosed on shave biopsy are upgraded to PDS at definitive excision.
Clinical features
- Solitary, rapidly growing, polypoid or ulcerated nodule.
- Almost exclusively on chronically sun-damaged skin of the head, neck and scalp of elderly Caucasian men (median age 80; M:F ~4:1).
- Associations with immunosuppression and prior radiotherapy.
- Often preceded by a long-standing actinic keratosis, BCC or scar at the site.
Histology & molecular
- Pleomorphic spindled and epithelioid cells with bizarre nuclei, abnormal mitoses and storiform architecture.
- Negative S100, SOX10, Melan-A (excludes melanoma); negative pan-cytokeratin/p63 (excludes spindle-cell SCC); negative desmin/SMA (excludes leiomyosarcoma); negative CD31 (excludes angiosarcoma).
- CD10 typically positive but non-specific.
- Massive UV-induced TP53 and telomerase reverse transcriptase promoter mutations; NOTCH1/2 mutations.
Imaging
- MRI of the affected region — defines depth of subcutaneous, fascial and muscular invasion.
- CT chest/abdomen/pelvis — staging for distant metastasis (lung most common).
- USS or CT of regional lymph node basin.
Management
- Wide local excision with at least 2 cm clinical margins to fascia, en-bloc with deep fascia where involved; reconstruction with skin graft or flap.
- Mohs micrographic surgery is increasingly used at experienced centres with comparable local control.
- Sentinel lymph node biopsy — considered for high-risk lesions, although evidence base is limited.
- Adjuvant radiotherapy for incomplete margins, multiple adverse histological features or recurrent disease.
- Systemic therapy for metastatic PDS is poorly defined; doxorubicin / ifosfamide regimens borrowed from soft-tissue sarcoma guidelines; checkpoint inhibitor responses reported.
Prognosis
Local recurrence 10–30%; regional or distant metastasis 10–20% (skin, parotid, lung). 5-year disease-specific survival 70–80%. AFX, in contrast, has near-zero metastatic risk. Follow-up should include clinical examination of the primary site and nodal basins: every 3 months in year 1, every 6 months in years 2–5, then annually thereafter for long-term surveillance; imaging is individualised by MDT according to depth, margins, recurrence, symptoms and metastatic risk.
References
- Tardío JC et al. Pleomorphic dermal sarcoma: a more aggressive neoplasm than previously estimated. J Cutan Pathol; 2016.
- Soleymani T et al. Pleomorphic dermal sarcoma — review. Dermatol Surg; 2020.
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