Purpose: Fumarate hydratase–deficient renal cell carcinoma (FH-RCC) is a rare, aggressive form of RCC associated with hereditary leiomyomatosis and RCC syndrome. Evidence for systemic therapy efficacy is lacking. Experimental Design: We studied clinical and genomic characteristics of FH-RCC, including response [objective response rate (ORR)] to systemic therapies and next-generation sequencing (NGS). Patients with metastatic FH-RCC, defined by presence of pathogenic germline or somatic FH mutation plus IHC evidence of FH loss, were included. Results: A total of 28 of 32 included patients (median age 46; range, 20–74; M:F, 20:12) underwent germline testing; 23 (82%) harbored a pathogenic FH germline variant. Five (16%) were negative for germline FH mutations; all had biallelic somatic FH loss. Somatic NGS (31/32 patients) revealed co-occurring NF2 mutation most frequently (n = 5). Compared with clear-cell RCC, FH-RCC had a lower mutation count (median 2 vs. 4; P < 0.001) but higher fraction of genome altered (18.7% vs. 10.3%; P = 0.001). A total of 26 patients were evaluable for response to systemic therapy: mTOR/VEGF combination (n = 18, ORR 44%), VEGF monotherapy (n = 15, ORR 20%), checkpoint inhibitor therapy (n = 8, ORR 0%), and mTOR monotherapy (n = 4, ORR 0%). No complete responses were seen. Median overall and progression-free survival were 21.9 months [95% confidence interval (CI): 14.3–33.8] and 8.7 months (95% CI: 4.8–12.3), respectively. Conclusions: Although most FH-RCC tumors are due to germline FH alterations, a significant portion result from biallelic somatic FH loss. Both somatic and germline FH-RCC have similar molecular characteristics, with NF2 mutations, low tumor mutational burden, and high fraction of genome altered. Although immunotherapy alone produced no objective responses, combination mTOR/VEGF therapy showed encouraging results.

Activation of the phosphatidylinositol-3 kinase (PI3K) pathway is a critical step in oncogenesis and plays a role in the development of treatment resistance for both estrogen receptor (ER) positive and human epidermal growth factor receptor 2 (HER2) positive breast cancers. Hence, there have been efforts to therapeutically inhibit this pathway. Areas covered: Several inhibitors of PI3K are now progressing through clinical trials with varying degrees of efficacy and toxicity to date. Numerous unresolved questions remain concerning the optimal isoform selectivity of PI3K inhibitors and use of predictive biomarkers. This review examines the most important PI3K inhibitors in ER positive breast cancer to date, with a particular focus on their role in overcoming endocrine therapy resistance and the possible use of PIK3CA mutations as a predictive biomarker. Expert opinion: We discuss some of the emerging challenges and questions encountered during the development of PI3K inhibitors from preclinical to phase III studies, including other novel biomarkers and future combinations to overcome endocrine resistance.

GISTs are the most common mesenchymal neoplasms of the gastrointestinal tract. The last 20 years have been revolutionary in the understanding of these tumours and began with the discovery of c-KIT, a proto oncogene that when mutated forms the molecular basis for the growth and development of these malignancies. Surgery was previously considered to be the only treatment modality in both local and advanced disease, however, the introduction of immunotherapy agents such as tyrosine kinase inhibitors has had profound effects on how we now approach and manage these tumours. These novel agents have significantly reduced the frequency of disease recurrence and dramatically improved survival, and serve as a model for the study of targeted therapies in other solid tumors. We present a review of gastrointestinal stromal tumours and consider the current evidence based detection and management of these unique tumors.

Osteopoikilosis is an uncommon cause of multiple osteosclerotic bone lesions. The skeletal changes of osteopoikilosis (synonyms: osteopathia condensans disseminata, spotted bone) were first described by Stieda in 1905 and subsequently by Albers-Schoenberg (1915). Radiologically, the lesions consist of multiple wellcircumscribed round or oval opacities, each 1–10 mm in diameter. The mottling is more marked in the epiphyses and metaphyses of the long bones and the pelvis, but is also common in the spongiosa of the phalanges, carpal and tarsal bones. The changes are more common in men than women and usually present in adulthood, although osteopoikilosis has been reported in children. Familial aggregation has been described, and autosomal dominant inheritance with variable expression is proposed (Schoenenberg, 1975). Osteopoikilosis should be considered in the differential diagnosis of multiple osteosclerotic bone lesions, but is a relatively uncommon finding. Serowy (1956) could find only 100 reported cases in the literature over a 25-year period since its initial description, and Jonasch (1955) found only 12 cases of osteopoikilosis in a series of 21000 radiographs.

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