The potential contribution of fluorescent in situ hybridization analysis to the cytopathological diagnosis of Merkel cell carcinoma

Mutational analysis of merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine malignancy that is associated with a poor prognosis. The pathogenesis of MCC is not well understood, and despite a recent plethora of mutational analyses, we have yet to find a set of signature mutations implicated in the majority of cases. Mutations, including TP53, Retinoblastoma and PIK3CA, have been documented in subsets of patients. Other mechanisms are also likely at play, including infection with the Merkel cell polyomavirus in a subset of patients, dysregulated immune surveillance, epigenetic alterations, aberrant protein expression, posttranslational modifications and microRNAs. In this review, we summarize what is known about MCC genetic mutations and chromosomal abnormalities, and their clinical significance. We also examine aberrant protein function and microRNA expression, and discuss the therapeutic and prognostic implications of these findings. Multiple clinical trials designed to selectively target overexpressed oncogenes in MCC are currently underway, though most are still in early phases. As we accumulate more molecular data on MCC, we will be better able to understand its pathogenic mechanisms, develop libraries of targeted therapies, and define molecular prognostic signatures to enhance our clinicopathologic knowledge.

Fine-needle aspiration cytology of Merkel cell carcinoma-a review of 69 cases

This study reviewed the clinical presentation, cytologic findings, and the immunophenotype of 69 Merkel cell carcinoma (MCC) cases sampled by fine-needle aspiration (FNA).  Demographic and clinical data, the cytology findings, and results of ancillary testing were reviewed.  Median patient age was 78 years (37-104) with a 1:1.8 female to male ratio. The most common FNA sites sampled included lymph nodes in the neck, the axillary region, the inguinal region and the parotid gland. Most patients had a history of MCC (68%) and/or non-MCC malignancy (70%).  The common cytologic pattern was a cellular smear with malignant cells arranged in a dispersed pattern with variable numbers of disorganized groups of cells. Cytoplasm was scant or absent and nuclei showed mild to moderate anisokaryosis, stippled chromatin, inconspicuous nucleoli, and nuclear molding. Numerous apoptotic bodies were often present.  Cell block samples (28 cases) were usually positive for cytokeratins in a perinuclear dot pattern, including 88% of cases with CK20 positivity. CD56 was the most sensitive (95%) neuroendocrine marker on cell blocks and was also positive with flow cytometry in nine cases tested.  MCC is most commonly seen in FNA specimens from the head and neck of elderly patients, often with a history of previous skin lesions. Occasional cases present in younger patients and some may be mistaken for other round blue cell tumors, such as lymphoma. CD 56 may be a useful marker in cell block preparations and in flow cytometric analysis of MCC.