Clinical and dermoscopic features of combined cutaneous squamous cell carcinoma (SCC)/neuroendocrine [Merkel cell] carcinoma (MCC)

Abstract

Background Merkel cell carcinoma (MCC) is a neuroendocrine carcinoma, associated with Merkel cell polyomavirus. MCC admixed with squamous cell carcinoma (SCC) is unassociated with polyomavirus, and is genetically distinct. Objective We sought to distinguish clinically and dermoscopically between MCC and SCC/MCC. Methods We compared patient data for SCC/MCC (n = 26) and MCC (n = 20), and reviewed clinical and dermoscopic images (n = 9) of SCC/MCC. Results Patients with SCC/MCC were older (median 76.5 vs 69 years) and more often male (77% vs 60%), and had more nonmelanoma skin cancer (85% vs 25%), malignant extracutaneous tumors (25% vs 5%), lymphoproliferative disorders (23% vs 10%), and immunodeficient/proinflammatory states (77% vs 35%). In all, 58% of SCC/MCC versus 10% of MCC were clinically diagnosed nonmelanoma skin cancer. Patients with SCC/MCC had more metastases (77% vs 40%), more treatment failures (53% vs 45%), shorter survival (41 vs 54 months), and more death from disease (50% vs 40%). SCC/MCC demonstrated marked scale (7/9), and telangiectasia (1/9). Dermoscopically, small dotted and short linear irregular peripheral vessels and central milky-red areas with large-diameter arborizing vessels were seen. Limitations The rarity of SCC/MCC limits available data. Conclusions SCC/MCC is aggressive, arising within elderly patients’ chronically ultraviolet-exposed skin, often in the setting of immunosuppression or inflammation. Dermoscopically, polymorphous vessels in lesions suspicious for nonmelanoma skin cancer are suggestive.

Merkel cell carcinoma with divergent differentiation

“…Disease extent at diagnosis is strongly predictive of prognosis, with the estimated 5‐year overall survival for local, nodal and distant disease being 51%, 35% and 14%, respectively . Evidence for the impact of divergent differentiation on prognosis is mixed, as the rarity of the entity means that most published case series have had small numbers . The main clinical import of divergent differentiation is the potential for misdiagnosis as a less aggressive skin tumour (e.g.…”

“…24 Evidence for the impact of divergent differentiation on prognosis is mixed, as the rarity of the entity means that most published case series have had small numbers. 6,7,10,12,22,25 The main clinical import of divergent differentiation is the potential for misdiagnosis as a less aggressive skin tumour (e.g. SCC or an adnexal tumour), which tend to have a better prognosis.…”

Merkel Cell Carcinoma

“…The second group of patients more commonly presents with tumors in sun-damaged skin of the head and neck, in a background of other nonmelanoma skin cancers, and are clinically more likely to be diagnosed as a new nonmelanoma skin cancer (58%), with only 15% suspected to be benign. 4 Clinical features, such as overlying scale and nearby actinic keratoses, solar lentigines, and telangiectasia, are common. A third, smaller group of patients presents with nodal adenopathy, eventuating in a biopsy-diagnosis of apparently metastatic MCC of unknown primary skin site.…”

“…Evidence builds, however, that MCC with squamous differentiation is clinically different and harbors histologic and molecular signatures, similar to CK20-negative MCC, 32 of UV-related squamous epithelial tumors. 4,16,17 Such tumors show less CK20 and NF positivity and more p53 and follicular stem cell markers 16–18 and are always negative for MCV. Well-differentiated SCC is easily diagnosed.…”

Merkel cell carcinoma: literature review

“…As the MCC component often exists within the dermis, and not in the epidermis, dermis including biopsies should be carried out when evaluating potential NMSC (Non-Melanomatous Skin Cancer). This enables, not to miss an unrevealed deadly neuroendocrine element with a too superficial shave, causing delays in diagnosis and management of this aggressive and often fatal tumor [38]. Quantitative polymerase chain reaction (PCR) assay we used to detect MCPyV (Merkel Cell polyomavirus) DNA, this was found to be positive in 80% of cases [6,16].…”