Malignant mesothelioma is a rare cancer that arises from the mesothelial cells that line the pleural cavity and less commonly from the peritoneal lining of the abdomen and pelvis. Most pleural mesotheliomas arise in patients with a history of asbestos exposure, whereas the association of peritoneal mesotheliomas with exposure to asbestos and other potential carcinogens is less clear, suggesting that the genetic alterations which drive malignant peritoneal mesothelioma may be unique from those in pleural mesothelioma. Treatment options for all malignant mesotheliomas are currently limited, with no known targeted therapies available. To better understand the molecular pathogenesis of malignant peritoneal mesothelioma, we sequenced 510 cancer-related genes in 13 patients with malignant mesothelioma arising in the peritoneal cavity. The most frequent genetic alteration was biallelic inactivation of the BAP1 gene, which occurred in 9/13 cases, with an additional 2 cases demonstrating monoallelic loss of BAP1. All 11 of these cases demonstrated loss of BAP1 nuclear staining by immunohistochemistry, whereas the 2 tumors without BAP1 alteration and all 42 cases of histologic mimics in peritoneum (8 multilocular peritoneal inclusion cyst, 6 well-differentiated papillary mesothelioma of the peritoneum, 16 adenomatoid tumor, and 12 low-grade serous carcinoma of the ovary) demonstrated intact BAP1 nuclear staining. Additional recurrently mutated genes in this cohort of malignant peritoneal mesotheliomas included NF2 (3/13), SETD2 (2/13), and DDX3X (2/13). While these genes are known to be recurrently mutated in pleural mesotheliomas, the frequencies are distinct in peritoneal mesotheliomas, with nearly 85% of peritoneal tumors harboring BAP1 alterations versus only 20-30% of pleural tumors. Together, these findings demonstrate the importance of epigenetic modifiers including BAP1, SETD2, and DDX3X in mesothelial tumorigenesis and suggest opportunities for targeted therapies.

Metastases from pituitary carcinomas are rare lesions that can mimic other tumors on fine-needle aspiration biopsies. Two patients with primary pituitary neoplasms developed cervical lymph node metastases, which were sampled and diagnosed correctly using the fine-needle aspiration biopsy technique. These two cases demonstrate the varied cytologic patterns of pituitary neoplasms, ranging from uniform bland cells to cells with striking anaplastic features. The time period between the onset of symptoms and subsequent metastases is unpredictable as well, underscoring the need for an accurate clinical history before a meaningful cytologic interpretation is made.

A 15-year-old girl presented with a small, indolent mass near the knee joint. Light microscopy revealed a peculiar myxoid plexiform tumor composed of cytologically bland cells. Interpretation of the initial biopsy material was controversial. Subsequent immunohistochemical studies revealed tumor cells to be strongly reactive for epithelial membrane antigen (EMA) and negative for S-100 protein. Ultrastructural studies revealed tumor cells with long, thin, bipolar cell processes and discontinuous basal laminae. They had no epithelial or histiocytoid features. Admixed among the tumor cells were Schwann cells, but they represented a rare and scattered component of the overall cell population. These features are most consistent with a so-called perineurioma and contrast with those of plexiform neurofibroma and traumatic neuroma (two lesions strongly positive for S-100 protein and showing a distinctive EMA immunoreactivity pattern with focal peripheral staining of neural bundles).

Lichen myxedematosus is characterized by deposits of mucin in the dermis. Treatment can be systemic or local, depending on the clinical findings. We present a patient with pedunculated lesions on his nose, and a generalized thickening of his facial skin. The patient requested treatment of his nasal lesions. We elected to remove his nodules surgically using the carbon dioxide (CO2) laser. The technique is described and treatment options are reviewed.

Le 4 août 2020, vers 18h00, un entrepôt du port de Beyrouth contenant 2 750 tonnes de nitrate d’ammonium a explosé engendrant la plus grande explosion urbaine depuis Hiroshima et Nagasaki. Au cœur de ce désastre, la Croix-Rouge libanaise (CRL) a répondu à l’appel, et s’est déployée sur la totalité de la zone sinistrée offrant tout genre de service au peuple dévasté. Au total, plus de 4 000 patients ont été traités sur place et plus de 2 600 ont été transportés vers les hôpitaux de Beyrouth et du Mont Liban. Dans une époque où le Liban est profondément secoué par une crise économique étouffante et par la pandémie de la COVID-19, les défis rencontrés ont été majeurs. La documentation de cet évènement et l’évaluation des réponses de la CRL sont des éléments clés pour l’amélioration de la gestion de catastrophe. Vue la rareté du contexte, les leçons à tirer sont nombreuses.