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A 79-year-old man presented with a 6-month history of four new painless enlarging scalp lesions. He had a strong history of sun exposure but otherwise no previous skin cancers. On examination, the lesions were suspicious for squamous cell carcinoma including a raised anterior scalp lesion measuring 4×7 mm with an overlying crust (figure 1). The lesions were removed by standard margin excisions down to the periosteum and the areas reconstructed with split skin grafts.
Histological analyses revealed the anterior scalp lesion to be a pleomorphic dermal sarcoma (PDS). The other lesions were confirmed to be low risk squamous cell carcinoma and actinic keratosis. All lesions had clear margins (>1 mm) except for the PDS, which had a close deep margin of 0.3 mm and demonstrated focal invasion to the galea, whereas peripheral margins were clear by around 4 mm. Sections of the PDS showed a poorly circumscribed tumour, arising in sun-damaged skin, which expanded the dermis and infiltrated into and through the subcutis (figure 2). Tumour cells were variably epithelioid and spindled, with focal cytological atypia, including prominent nucleoli. Occasional multinucleated forms were observed and atypical mitoses were present. There was no evidence of tumour necrosis, nor lymphovascular or perineural invasion. Immunostaining was negative for MNF116, AE1/AE3, CK5/6, p63, desmin, S100, SOX10, CD34 and CD31. The immunohistochemical panel excluded other possible differential diagnoses, including squamous cell carcinoma, melanoma and angiosarcoma.
The patient was reviewed in a skin multidisciplinary team discussion and surgical re-excision was recommended for the PDS close deep margin, which he is currently awaiting.
PDS is characteristically a fast-growing, ulcerated, exophytic, bleeding skin tumour, similar to atypical fibroxanthomas, but with metastatic potential and is histologically distinguished by necrosis, or deep subcutis, lymphovascular or perineural invasion.1 2 Little is known about the best clinical treatment due to its rarity. Hence, a systematic search in PubMed of ‘pleomorphic dermal sarcoma’” was conducted in April 2021, netting 134 articles, from which 15 were longitudinal studies that provided outcomes specific to PDS (table 1).2–16 Reported characteristics and outcomes (besides age) were pooled via random-effects meta-analysis using the generalised linear mixed model with logit transformation, along with Clopper-Pearson CIs for individual studies.17 Heterogeneity was assessed via the I2 statistic and the likelihood-ratio test.18 Statistical tests were conducted using the meta package in R (V.3.6.0).19 20
In six studies,2 3 8 10 12 14 PDS primarily affects older individuals (weighted mean age=80.64), and from meta-analysis, predominantly occurs in men (82.80%, 95% CI=72.37% to 89.95%, I2=62.1%, likelihood-ratio test p=0.011). Meta-analyses further showed that PDS is largely found on the scalp (68.92%, 95% CI=57.99% to 78.08%, I2=54.9%, p=0.019) in five studies,2 3 8 12 14 or the face (13.05%, 95% CI=4.16% to 34.18%, I2=88.1%, p<0.0001) in six studies.2 3 8 10 12 14 Recurrence rate was 23.80% (95% CI=17.97% to 30.82%, I2=11.5%, p=0.037) in eight studies,2–4 8–10 12 14 with 19.92% (95% CI=15.43% to 25.32%, I2=0%, p=0.050) local recurrence and 7.14% (95% CI=4.55% to 11.05%, I2=0%, 0.261) metastasis over nine studies (mean follow-up 13–46.4 months).2–4 6 8–10 12 14 Among four studies,2 3 8 14 87.25% (95% CI=3.11% to 99.93%, I2=91.0%, p=0.0003) of local recurrences were due to incomplete removal or inadequate margins. There is limited evidence showing radiotherapy is effective.2 6 12 There is also limited evidence showing modified Mohs micrographic surgery offers better prognosis than conventional surgery.13 Conversely, margins <2 cm predispose worse prognosis.12 Two metastatic cases were successfully managed by chemotherapy.2 8
Pleomorphic dermal sarcoma is a rare cancer that presents primarily in older men on sun-exposed areas such as the scalp.
Due to the metastatic potential of pleomorphic dermal sarcoma, it is important not to miss this diagnosis and to ensure complete resection of the tumour.
Contributors ACQL, SM and KYW drafted the case report. ACQL conducted the systematic review and meta-analysis. ACQL, SM and KYW critically revised and approved the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.