Merkel cell carcinoma associated with stable chronic hemodialysis: A report of two cases.

Merkel cell carcinoma (MCC) is a rare but aggressive cutaneous malignancy associated with the Merkel cell polyomavirus (MCPyV). Multiple studies have shown that the incidence of MCC is higher among immunocompromised individuals than among the general population. In fact, immunosuppressed individuals account for approximately 10% of the MCC patient population.

Crater/ulcerated form of infundibular squamous cell carcinoma: A possible distinct entity as a malignant (or high-grade) counterpart to keratoacanthoma.

Follicular squamous cell carcinoma (SCC) with infundibular differentiation includes the common and crater forms of infundibular SCC. We previously considered the crater/ulcerated infundibular SCC to be a progressive condition of the common form and histopathologically studied an additional five cases of the crater/ulcerated infundibular SCC, the results of which suggested the following characteristic histopathological features and possible developmental process in this type of SCC: (i) a considerable number of continuous hyperplastic follicular infundibula, which may develop at the beginning of the disease; (ii) hyperplastic infundibula exhibiting an abrupt or gradual transition to the SCC component, which frequently change relative to the neoplastic infundibular canal; and (iii) the presence of multiple sites of branching of the neoplastic infundibular canals and/or complete involvement of large cysts in the neoplastic process over the center of the lesion, resulting in ulceration. Based on these histopathological findings, we considered that crater/ulcerated infundibular SCC involve a considerable number of continuous follicular infundibula from the start, although some cases may develop from the common form.