Merkel cell carcinoma with lymphoepithelioma-like pattern: a case report of an exceedingly rare variant of merkel cell carcinoma with lymph node metastases at presentation.

Merkel cell carcinoma (MCC) or primary neuroendocrine carcinoma of the skin is a rare neoplasm with aggressive behavior. Primary lymphoepithelioma-like (LEL) carcinoma of the skin is a recently described exceptional tumor, with a relatively good prognosis, and is characterized by a neoplastic epithelial component associated with a dense lymphoid stroma. Rarely, MCC shows a marked lymphocytic host response or can even mimic a LEL carcinoma. We report a new case of MCC mimicking an LEL carcinoma in a 72-year-old male; the diagnosis of MCC was made on the basis of the morphology and immunohistochemical findings. We present through this case an exceptional pattern of MCC which can be misleading, and we insist on differential diagnoses.

Usefulness of molecular biology performed with formaldehyde-fixed paraffin embedded tissue for the diagnosis of combined pulmonary invasive mucormycosis and aspergillosis in an immunocompromised patient.

Immunocompromised patients who develop invasive filamentous mycotic infections can be efficiently treated if rapid identification of the causative fungus is obtained. We report a case of fatal necrotic pneumonia caused by combined pulmonary invasive mucormycosis and aspergillosis in a 66 year-old renal transplant recipient. Aspergillus was first identified during the course of the disease by cytological examination and culture (A. fumigatus) of bronchoalveolar fluid. Hyphae of Mucorales (Rhizopus microsporus) were subsequently identified by culture of a tissue specimen taken from the left inferior pulmonary lobe, which was surgically resected two days before the patient died. Histological analysis of the lung parenchyma showed the association of two different filamentous mycoses for which the morphological features were evocative of aspergillosis and mucormycosis. However, the definitive identification of the associative infection was made by polymerase chain reaction (PCR) performed on deparaffinized tissue sections using specific primers for aspergillosis and mucormycosis. This case demonstrates that discrepancies between histological, cytological and mycological analyses can occur in cases of combined mycotic infection. In this regard, it shows that PCR on selected paraffin blocks is a very powerful method for making or confirming the association of different filamentous mycoses and that this method should be made available to pathology laboratories.