Salivary gland hyalinizing clear‐cell carcinoma with cutaneous metastasis: A rare and deceptive tumor

Clear‐cell carcinoma (CCC) is an uncommon malignant tumor of minor salivary glands. It characteristically has a low‐grade morphology and a favorable outcome by most reports. An EWSR1‐ATF1 fusion can be detected in the majority of cases. We present a rare case of CCC, which had an aggressive course with the development of cutaneous metastases. Practicing dermatopathologists should be aware of this tumor given its low‐grade appearance and histopathologic resemblance to other primary cutaneous adnexal and metastatic neoplasms.     

Panniculitis in a 3‐year‐old child with Fanconi anemia‐associated bone marrow hypoplasia heralds transformation to acute myeloid leukemia

Fanconi anemia is a rare, autosomal recessive genomic instability disorder characterized by congenital limb anomalies, panmyelopathy and a high risk of malignancy, principally acute myeloid leukemia. Hematologic malignancy presenting with acute febrile neutrophilic dermatosis (Sweet syndrome), both deep and superficial forms, is well described in Fanconi anemia patients but is a rare phenomenon in otherwise healthy children. We present a case of panniculitis (presumptive subcutaneous Sweet syndrome) heralding transformation to acute myeloid leukemia in a 3‐year‐old boy with a severe Fanconi anemia phenotype.     

Mutant C9orf72 human iPSC-derived astrocytes cause non-cell autonomous motor neuron pathophysiology

Mutations in C9orf72 are the most common genetic cause of amyotrophic lateral sclerosis (ALS). Accumulating evidence implicates astrocytes as important non-cell autonomous contributors to ALS pathogenesis, although the potential deleterious effects of astrocytes on the function of motor neurons remains to be determined in a completely humanized model of C9orf72-mediated ALS. Here, we use a human iPSC-based model to study the cell autonomous and non-autonomous consequences of mutant C9orf72 expression by astrocytes. We show that mutant astrocytes both recapitulate key aspects of C9orf72-related ALS pathology and, upon co-culture, cause motor neurons to undergo a progressive loss of action potential output due to decreases in the magnitude of voltage-activated Na⁺ and K⁺ currents. Importantly, CRISPR/Cas-9 mediated excision of the C9orf72 repeat expansion reverses these phenotypes, confirming that the C9orf72 mutation is responsible for both cell-autonomous astrocyte pathology and non-cell autonomous motor neuron pathophysiology.