Lymph Node Metastasis With Both Components of Combined Cutaneous Squamous Cell Carcinoma/Merkel Cell (Neuroendocrine) Carcinoma

Combined Merkel Cell Carcinoma and Squamous Cell Carcinoma: A Systematic Review

Combined Merkel cell carcinoma (MCC) and squamous cell carcinoma (SCC) have classically been regarded as more aggressive than conventional, pure, Merkel cell polyomavirus (MCPyV)-positive MCC. It is still unknown whether combined MCC and SCC are more aggressive than pure, MCPyV-negative MCC, and the origin of both the SCC and MCC elements of these combined tumors has not been elucidated. The main objective of this systematic review was to assess whether combined MCC and SCC tumors are associated with a worse prognosis than pure MCC; the secondary goals were the characterization of the clinical and histopathological features of these combined neoplasms. A total of 38 studies, including 152 patients, were selected for review. In total, 76% of the cases were MCPyV-negative, whereas 4% were MCPyV-positive. The most frequent histopathological pattern was that of an SCC in situ combined with a dermal MCC (36%), followed by both an in situ and invasive SCC combined with a dermal MCC (20%). Forty-seven percent of all cases fitted in the morphology of the so-called "collision tumors". Three combined MCC cases that would fit in the morphological category of collision tumors presented both squamous and neuroendocrine elements in their respective nodal metastases. The mean overall survival was 36 months, comparable to that of pure, MCPyV-negative MCC. This review found similarly aggressive behavior for combined MCC and SCC and pure, MCPyV-negative MCC. Preliminary data strongly suggest that all MCPyV-negative MCC tumors, whether combined or pure, are part of a common spectrum.

Detection of Merkel Cell Polyomavirus (MCPyV) DNA and Transcripts in Merkel Cell Carcinoma (MCC)

Merkel cell polyomavirus (MCPyV) is the etiological agent of the majority of Merkel cell carcinoma (MCC): a rare skin tumor. To improve our understanding of the role of MCPyV in MCCs, the detection and analysis of MCPyV DNA and transcripts were performed on primary tumors and regional lymph nodes from two MCC patients: one metastatic and one non-metastatic. MCPyV-DNA was searched by a quantitative polymerase chain reaction (qPCR), followed by the amplification of a Large T Antigen (LTAg), Viral Protein 1 (VP1) and Non-Coding Control Region (NCCR). LTAg and VP1 transcripts were investigated by reverse-transcription PCR (RT-PCR). Viral integration was also studied, and full-length LTAg sequencing was performed. qPCR revealed that the primary tumor of both patients and the lymph node of one patient was positive for the small t-antigen, with an average value of 7.0 × 102 copies/µg. The same samples harbored LTAg, NCCR and VP1 DNA. Sequencing results showed truncated LTAg with the conserved retinoblastoma (Rb) protein binding motif and VP1 and NCCR sequences identical to the MCC350 strain. RT-PCR detected LTAg but not VP1 transcripts. The MCPyV genome was integrated into the primary tumor of both patients. The results confirmed the connection between MCPyV and MCC, assuming integration, LTAg truncation and Rb sequestration as key players in MCPyV-mediated oncogenesis.

Combined Merkel cell carcinoma and cutaneous squamous cell carcinoma with lymph node metastases: Report of two cases

Merkel cell carcinoma (MCC) is an infrequent, aggressive cutaneous neoplasm, that typically affects the photodamaged skin of elderly individuals, and immunosuppressed patients. Because a subset of MCC is closely related to UV radiation, MCC can develop concurrently with other tumors, most commonly, as a combined tumor with squamous cell carcinoma (SCC). These combined tumors appear to represent a distinct disease process from pure MCC, as they are mostly Merkel cell polyomavirus (MCPyV) negative, and show a more aggressive behavior. We present two additional cases of combined MCC and SCC with nodal metastases, one of which was MCPyV positive. Two different subtypes of MCC have been proposed based on their origin: a true neuroendocrine carcinoma, that is MCPyV positive and has a dermal origin, and a UV-related SCC with neuroendocrine differentiation. This theory could explain why MCC can develop concurrently with SCC, and why these combined cases are generally MCPyV negative. However, it fails to explain the minority of combined MCC and SCC tumors that are MCPyV positive. Because both our patients had a history of chronic UV exposure, we hypothesize that UV radiation probably played a major role in the pathogenesis of these tumors, while MCPyV integration probably acted as an additional trigger.

Combined Merkel Cell Carcinoma with Nodal Presentation: Report of a Case Diagnosed with Excisional but Not Incisional Biopsy and Literature Review

Merkel cell carcinoma (MCC) is a rare primary neuroendocrine carcinoma (NEC) of the skin. As compared to pure MCCs, combined MCCs are aggressive and exhibit a higher probability of metastasis. A correct diagnosis might be missed, especially when the biopsy sample is too small or too superficial. We report a 79-year-old Taiwanese male who presented with lymphadenopathy suspicious for lymphoma. A nodal biopsy showed metastatic NEC. A skin tumor in the lower back was identified, and an incisional biopsy showed only squamous cell carcinoma (SCC). A subsequent excisional biopsy was performed based on the advice of the senior pathologist because of the presence of metastatic nodal NEC. Finally, a diagnosis of combined MCC and SCC was confirmed. Our literature review identified 13 cases of combined MCC with nodal metastasis as initial presentations, all with an aggressive clinical course. Both the MCC and non-MCC components could be present in the metastatic nodes. Metastases of pure MCC cells were observed in three combined MCCs in sun-protected areas, probably pointing to a distinct pathogenesis. Excision or punch biopsy to include the deep dermal NEC component is recommended as timely diagnosis is mandatory for appropriate management of patients with this rare skin cancer.

Morphological patterns of metastases from combined Merkel cell carcinomas: study of an eastern Canadian cohort of cases

Combined Merkel cell carcinomas are hybrid tumors composed of neuroendocrine and other phenotypic (usually squamous) elements. They form a minority of Merkel cell carcinomas (MCCs) as a whole, are usually Merkel cell polyomavirus-negative, and have rarely been segregated for specific study. Sporadic reports have indicated that metastases from these tumors can show a combined phenotype. We retrospectively studied 38 cases (24 men [63%], 14 women [37%], mean age 78 years [range, 46-99 years]) of combined MCC. Metastases occurred in 20 patients (53%) (at presentation and/or in follow-up [mean 38 months (range, 0.6-185 months)]). Those from 17 individuals (45%) were examined microscopically. These were mainly nodal in distribution. In 12 patients (71%), the secondary deposits were of pure neuroendocrine type, whereas in 5 (29%), combined deposits were identified. Squamous elements were the most common divergent component, in the primary and secondary tumors. The combined metastases varied from obvious squamous nests in a neuroendocrine background to scattered bizarre tumor giant cells expressing CK5/6 on immunohistochemistry. In one case, individual nodes within a single basin displayed purely squamous or purely neuroendocrine deposits. The mean overall survival in the cohort was 48 months (range, 30-67 months) and the mortality was 82%. Our work sheds light on the frequency and patterns of metastases in combined MCCs. In concert with the poor outcome data documented by others, it also raises a question as to the potential prognostic significance of a combined phenotype per se, independent of a virus-negative status and other variables. This issue deserves further study.

Primary cutaneous phalangeal neuroendocrine/squamous cell carcinoma with mixed axillary metastasis

Cutaneous neuroendocrine tumours are rare and aggressive tumours associated with advanced age and immunosuppression. They are typically characterised by a high rate of local recurrence and nodal disease. The presence of a mixed squamous cell component is rare. These tumours are uncommonly found on the hand. We present a case and histological images of a 78-year-old woman with a primary CK20 negative TTF-1 positive cutaneous neuroendocrine tumour with squamous dedifferentiation arising from the fifth digit with axillary metastasis showing a mixed phenotype. Initial biopsy of the lesion was positive for chromogranin, synaptophysin and TTF-1, but negative for CK20, Melan-A and S100. After CT of the thorax abdomen and pelvis and octreotide single positron emission CT demonstrated a 15 mm axillary metastasis and no evidence of distal disease, our patient underwent an amputation of the affected digit and an axillary lymph node dissection. She is currently awaiting adjuvant chemoradiotherapy. Only two cases are reported in the literature to have mixed squamous/neuroendocrine features. We present the first case which is CK20 negative and TTF-1 positive.