Osteochondromyxoma of bone: a congenital tumor associated with lentigines and other unusual disorders

Osteochodromyxoma presenting as case of congenital nasolacrimal duct obstruction

Purpose

We report the case of a 10-month-old with nasolacrimal duct obstruction (NLDO) associated with osteochondromyxoma (OMX), a very rare bone tumor.

Observations

A 10-month-old boy presented with a 6-month history of right eye epiphora not responding to digital massage and topical steroid-antibiotics eye drops. The ophthalmic exam showed right medial canthal swelling. During the ophthalmic exam an abnormal snoring sound was noted. The mother also reported that patient experienced frequent upper respiratory tract infections. Inspection of nostrils showed a right nasal lesion that upon comprehensive evaluation by ENT and pathology teams turned out to be an OMX with loss of PRKAR1A expression. Further genetic testing confirmed the Carney complex (CNC) diagnosis and the patient was referred to multidisciplinary care. To the best of our knowledge, this is one of the first cases of OMX-induced NLDO, where a typical looking congenital NLDO ended up with a diagnosis of a rare genetic disease.

Conclusion and Importance

We have described a case of OMX of the nasal cavity masquerading as congenital NLDO. This case emphasizes that NLDO is not always congenital if presenting within the first few months of life. It is important to obtain a thorough history and exam to evaluate potential differential diagnoses to guide subsequent decision-making steps.

Neonatal osteoblastic tumor with a novel PTBP1::FOSB fusion

Congenital/neonatal bone neoplasms are extremely rare. We present the case of a patient with a neonatal bone tumor of the fibula that had osteoblastic differentiation and a novel PTBP1::FOSB fusion. FOSB fusions are described in several different tumor types, including osteoid osteoma and osteoblastoma; however, these tumors typically present in the second or third decade of life, with case reports as young as 4 months of age. Our case expands the spectrum of congenital/neonatal bone lesions. The initial radiologic, histologic, and molecular findings supported the decision for close clinical follow-up rather than more aggressive intervention. Since the time of diagnosis, this tumor has undergone radiologic regression without treatment.

An adolescent case of sellar osteochondromyxoma in the setting of spondyloepiphyseal dysplasia

PURPOSE

Osteochondromyxomas (OMX) are rare congenital bone tumors that have only been described in the context of Carney complex syndrome (CNC). Data on OMX as a separate entity and in association with other disorders remain limited, making both diagnosis and treatment difficult.

METHODS

A case report of a 17-year-old female diagnosed with sellar OMX is presented in the setting of spondyloepiphyseal dysplasia (SED). We discuss the radiographic and histopathological interpretations in addition to reviewing the current literature on OMX.

RESULTS

A successful gross total resection of the tumor was achieved via an endonasal endoscopic transsphenoidal approach. A diagnosis was established radiographically and pathologically.

CONCLUSION

The diagnosis and treatment of OMX are best achieved via tissue biopsy. Following confirmed osteochondromyxoma cases long term for recurrence and outcomes will be essential in understanding its natural tumor history and in establishing standard treatments.

Benign bony tumors of the paranasal sinuses, orbit, and skull base

Benign bony tumors of the skull base and paranasal sinuses are uncommon entities, with an overall higher incidence in males. Benign bony tumors may lead to local expansion with resultant mass effect of potentially critical structures. Some benign bony tumors may undergo malignant transformation. This article reviews the presentation and management of benign bone tumors of the skull base and paranasal sinuses with special consideration to involvement of the adjacent orbit, intracranial and critical neurovascular structures. This review covers tumor incidence, location, gross and histologic appearance as well as radiographic findings, treatment, and recurrence rates. Tumors discussed in this article include osteochondromas, osteomas, osteoid osteomas, aneurysmal bone cysts, fibrous dysplasia, giant cell tumors, cemento-ossifying fibroma, ameloblastic fibro-odontoma, ecchordosis physaliphora, chondromyxoid fibroma, primary chronic osteomyelitis, primary chronic osteomyelitis, osteochondromyxoma, and dense bone islands.

Fibrous dysplasia animal models: A systematic review

BACKGROUND

Fibrous dysplasia (FD) is a rare genetic bone disorder resulting in an overproduction of cAMP leading to a structurally unsound tissue, caused by a genetic mutation in the guanine nucleotide-binding protein gene (GNAS). In order to better understand this disease, several animal models have been developed with different strategies and features.

OBJECTIVE

Conduct a systematic review to analyze and compare animal models with the causative mutation and features of FD.

METHODS

A PRISMA search was conducted in Scopus, PubMed, and Web of Science. Studies reporting an in vivo model of FD that expressed the causative mutation were included for analysis. Models without the causative mutation, but developed an FD phenotype and models of FD cell implantation were included for subanalysis.

RESULTS

Seven unique models were identified. The models were assessed and compared for their face validity, construct validity, mosaicism, and induction methods. This was based on the features of clinical FD that were reported within the categories of: macroscopic features, imaging, histology and histomorphometry, histochemical and cellular markers, and blood/urine markers.

LIMITATIONS

None of the models reported all features of FD and some features were only reported in one model. This made comparing models a challenge, but indicates areas where further research is necessary.

CONCLUSION

The benefits and disadvantages of every model were assessed from a practical and scientific standpoint. While all published reports lacked complete data, the models have nonetheless informed our understanding of FD and provided meaningful information to guide researchers in bench and clinical research.

Primary extradural tumors of the spinal column: A comprehensive treatment guide for the spine surgeon based on the 5th Edition of the World Health Organization bone and soft-tissue tumor classification

BACKGROUND

In 2020, the World Health Organization (WHO) published the 5th version of the soft tissue and bone tumor classification. Based on this novel classification system, we reviewed the current knowledge on all tumor entities with spinal manifestations, their biologic behavior, and most importantly the appropriate treatment options as well as surgical approaches.

METHODS

All tumor entities were extracted from the WHO Soft-Tissue and Bone Tumor Classification (5th Edition). PubMed and Google Scholar were searched for the published cases of spinal tumor manifestations for each entity, and the following characteristics were extracted: Growth pattern, ability to metastasize, peak age, incidence, treatment, type of surgical resection indicated, recurrence rate, risk factors, 5-year survival rate, key molecular or genetic alterations, and possible associated tumor syndromes. Surgical treatment strategies as well as nonsurgical treatment recommendations are presented based on the biologic behavior of each lesion.

RESULTS

Out of 163 primary tumor entities of bone and soft tissue, 92 lesions have been reported along the spinal axis. Of these 92 entities, 54 have the potential to metastasize. The peak age ranges from conatal lesions to 72 years. For each tumor entity, we present recommended surgical treatment strategies based on the ability to locally destruct tissue, to grow, recur after resection, undergo malignant transformation as well as survival rates. In addition, potential systemic treatment recommendations for each tumor entity are outlined.

CONCLUSION

Based on the 5th Edition of the WHO bone and soft tumor classification, we identified 92 out of 163 tumor entities, which potentially can have spinal manifestations. Exact preoperative tissue diagnosis and interdisciplinary case discussions are crucial. Surgical resection is indicated in a significant subset of patients and has to be tailored to the specific biologic behavior of the targeted tumor entity based on the considerations outlined in detail in this article.

Inherited Follicular Epithelial-Derived Thyroid Carcinomas: From Molecular Biology to Histological Correlates

Cancer derived from thyroid follicular epithelial cells is common; it represents the most common endocrine malignancy. The molecular features of sporadic tumors have been clarified in the past decade. However the incidence of familial disease has not been emphasized and is often overlooked in routine practice. A careful clinical documentation of family history or familial syndromes that can be associated with thyroid disease can help identify germline susceptibility-driven thyroid neoplasia. In this review, we summarize a large body of information about both syndromic and non-syndromic familial thyroid carcinomas. A significant number of patients with inherited non-medullary thyroid carcinomas manifest disease that appears to be sporadic disease even in some syndromic cases. The cytomorphology of the tumor(s), molecular immunohistochemistry, the findings in the non-tumorous thyroid parenchyma and other associated lesions may provide insight into the underlying syndromic disorder. However, the increasing evidence of familial predisposition to non-syndromic thyroid cancers is raising questions about the importance of genetics and epigenetics. What appears to be "sporadic" is becoming less often truly so and more often an opportunity to identify and understand novel genetic variants that underlie tumorigenesis. Pathologists must be aware of the unusual morphologic features that should prompt germline screening. Therefore, recognition of harbingers of specific germline susceptibility syndromes can assist in providing information to facilitate early detection to prevent aggressive disease.

Revisiting the WHO classification system of bone tumours: emphasis on advanced magnetic resonance imaging sequences. Part 2

Similarly to soft tissue tumours, the World Health Organisation (WHO) classification categorises bone tumours based on their similarity to normal adult tissue. The most recent WHO classification provides an updated classification scheme that integrates the biological behaviour of bone tumours, particularly cartilage-forming tumours, and tumours are now further subdivided as benign, intermediate (locally aggressive or rarely metastasising), and malignant. Radiologists play an important role in the detection and initial characterisation of bone tumours, with careful analysis of their matrix mineralisation, location, and overall anatomic extent including extra-compartmental extension and neurovascular invasion. Radiography remains central to the detection and characterisation of bone tumours; however, magnetic resonance imaging (MRI) is the ideal modality for local staging. This review will discuss the most recent updates to the WHO classification of bone tumours that are relevant to radiologists in routine clinical practice. The utility of advanced MRI sequences such as diffusion-weighted imaging, dynamic contrast enhanced sequences, and magnetic resonance spectroscopy that may provide insight into the biological behaviour of various bone tumours is highlighted.

Bone tissue and mineral metabolism in hereditary endocrine tumors: clinical manifestations and genetic bases

Inherited endocrine tumors are neoplasms of endocrine cells, transmitted via autosomal dominant germinal mutations. They present in two different forms: non-syndromic (patient has a single affected endocrine organ during his/her lifetime) or syndromic forms (multiple tumors in endocrine and non-endocrine organs during his/her lifetime).In addition to their common tumoral manifestations, many of these diseases present clinical affection of bone tissues and/or mineral metabolism, both as secondary complications of primary tumors and as primary defects due to genetic mutation. To date, few studies have documented these bone complications, and there are no systematic reviews in this area.We present a revision of medical literature about skeletal and mineral metabolism affections in inherited endocrine tumor syndromes, and studies, in cells and animal models, investigating the direct role of some genes, whose mutations are responsible for the development of endocrine tumors, in the regulation of bone and mineral metabolism.

An Unusual Presentation of Carney Complex

Carney complex (CNC) is a multiple neoplasia syndrome, characterized by pigmented lesions of the skin and mucosa, cardiac, cutaneous and other myxomas and multiple endocrine and non-endocrine tumors. Most of the cases have an inactivating mutation in the PRKAR1A gene. Osteochondromyxoma (OMX) is an extremely rare myxomatous tumor of bone, affecting 1% of CNC patients. Large cell calcifying Sertoli cell tumor (LCCSCT) is a testicular tumor affecting more than 75% of males with CNC. Here, we report an atypical case of CNC without typical pigmented skin lesions, presenting with a bone based tumor as the first manifestation. Initial presentation was for a recurrent, locally invasive intranasal tumor without definite diagnosis. Further clinical developments during follow up, central precocious puberty and testicular tumor with calcification, led to the diagnosis of LCCSCT, a CNC-related tumor. Histopathologic examination of the intranasal tumor was re-evaluated with this knowledge and OMX was diagnosed. Coexistence of OMX and LCCSCT suggested CNC. Genetic analysis revealed a heterozygous non-sense p.Trp 224* (c.672G>A) in the PRKAR1A gene. In our case, the diagnosis of OMX was delayed, because it is extremely rare and little is known about this tumor. Thus the aim of this report was to alert other clinicians to consider CNC if OMX is diagnosed.

Ring sign: an imaging sign for osteochondromyxoma in Carney complex

Background

To introduce the concept of "ring sign" and to evaluate its role in the diagnostic imaging of osteochondromyxoma in patients with Carney complex (CNC).

Methods

Three patients presenting osteochondromyxoma with CNC were included for evaluation of the ring sign on different imaging modalities, including radiographs, computed tomography, and magnetic resonance imaging. The literature was reviewed for further discussion.

Results

The ring sign in osteochondromyxoma could be seen on radiographs, computed tomography, and magnetic resonance images in all three patients at each of the involved sites. The morphological patterns and the number of ring signs varied by case, site, and imaging method. Some previous reports have shown images that contain ring signs, but do not identify them as such.

Conclusions

Ring sign can be considered as a relatively specific sign, helpful for the imaging diagnosis of osteochondromyxoma in the CNC.

[Updates to the WHO classification of bone tumours]

The fourth edition of the WHO Classification of Soft Tissue and Bone Tumours, published in 2013, extends the approach to describe genetics and pathology of these tumours in the context of epidemiological, clinical and imaging data, which was adopted in the third edition. Added are a few new entities, reclassifications and renamings. The most important point, also of clinical relevance and with consequences for treatment, is the introduction of a stratification of bone tumours based on their biological behaviour into three groups (benign, intermediate, malignant) in analogy to soft tissue tumours.

The Spectrum of Thyroid Gland Pathology in Carney Complex: The Importance of Follicular Carcinoma

The initial description of Carney complex (CNC) in 1985 included myxomas, spotty skin pigmentation, and endocrine overactivity (of the adrenal, the pituitary, and the testis). In 1997, thyroid neoplasms were found in 3 patients with CNC and involvement of the gland in the syndrome was apparent. Herein, we describe the clinical, pathologic, and follow-up findings in 26 patients with CNC and a disorder of the thyroid gland. The patients were predominantly middle-aged women with an asymptomatic thyroid mass. Four patients had hyperthyroidism, which was caused by follicular hyperplasia in 2 patients and by toxic adenoma in 2 others. Pathologic findings included benign lesions (follicular hyperplasia, nodular hyperplasia, and follicular adenoma) in 16 patients and carcinomas (follicular or papillary) in 10 patients. The follicular carcinomas had unusual features, multifocality, bilaterality, and lymph node metastasis. The tumor was fatal in 3 of 4 patients with a tumor ≥3 cm in diameter. One patient had an unusual multifocal microscopic follicular hyperplasia. Detection and treatment of the thyroid neoplasms in patients with CNC requires long-term follow-up of patients with the syndrome.

Carney complex: Two case reports and review of literature

Carney complex (CNC) is an extremely rare genetic syndrome of pigmented skin lesions, endocrine hyperfunction and myxoma. Given its diverse clinical manifestations, CNC is often misdiagnosed. Recognition of some special clinical manifestations and imaging features may help with the diagnosis. Early diagnosis of CNC would alert ongoing surveillance of tumors and complications; the prognosis of CNC may thus be improved by early treatment. Herein, we report two cases of CNC with bone lesions.

A novel splice site mutation of the PRKAR1A gene, C.440+5 G>C, in a Chinese family with Carney complex

BACKGROUND

Carney complex (CNC) is an extremely rare, multiple endocrine neoplasia syndrome that occurs in an autosomal dominant manner. Mutations in PRKAR1A have been reported to be a common genetic cause of CNC.

METHODS

In this study, we reported a Chinese pedigree of CNC that manifests mainly as spotty skin pigmentation and primary pigmented nodular adrenocortical disease. Whole blood samples of this pedigree were collected for DNA/RNA analysis. Polymerase chain reaction (PCR) and reverse-transcription polymerase chain reaction analyses were performed to amplify the 11 exons and adjacent introns of PRKAR1A. Direct sequencing was used to detect the mutation, and DNA from 70 Han Chinese people was extracted and sequenced as a control to estimate the frequency of the identified mutation.

RESULTS

Within the pedigree, ten patients with CNC were identified, and a novel heterozygous mutation (c.440+5 G>C in intron 4a) was identified in the PRKAR1A gene. PCR amplification of cDNA from the control subjects and patients was performed. Agarose gel electrophoresis showed only one wild-type band in the cDNA corresponding to the former group, whereas an extra band was present in samples from the latter group corresponding to the skipping of exon 4a; this confirms that the variant affects PRKAR1A splicing.

CONCLUSION

In conclusion, the c.440+5 G>C mutation is a new splice site mutation that has not been reported and has the potential to broaden the mutational spectrum of PRKAR1A that is associated with CNC, which would facilitate genetic diagnosis and counseling for CNC.

Murine models of osteosarcoma: A piece of the translational puzzle

Osteosarcoma (OS) is the most common cancer of bone in children and young adults. Despite extensive research efforts, there has been no significant improvement in patient outcome for many years. An improved understanding of the biology of this cancer and how genes frequently mutated contribute to OS may help improve outcomes for patients. While our knowledge of the mutational burden of OS is approaching saturation, our understanding of how these mutations contribute to OS initiation and maintenance is less clear. Murine models of OS have now been demonstrated to be highly valid recapitulations of human OS. These models were originally based on the frequent disruption of p53 and Rb in familial OS syndromes, which are also common mutations in sporadic OS. They have been applied to significantly improve our understanding about the functions of recurrently mutated genes in disease. The murine models can be used as a platform for preclinical testing and identifying new therapeutic targets, in addition to testing the role of additional mutations in vivo. Most recently these models have begun to be used for discovery based approaches and screens, which hold significant promise in furthering our understanding of the genetic and therapeutic sensitivities of OS. In this review, we discuss the mouse models of OS that have been reported in the last 3-5 years and newly identified pathways from these studies. Finally, we discuss the preclinical utilization of the mouse models of OS for identifying and validating actionable targets to improve patient outcome.

Cushing Syndrome in Carney Complex: Clinical, Pathologic, and Molecular Genetic Findings in the 17 Affected Mayo Clinic Patients

Carney complex (CNC) is a rare dominantly inherited multiorgan tumoral disorder that includes Cushing syndrome (CS). To establish the Mayo Clinic experience with the CS component, including its clinical, laboratory, and pathologic findings, we performed a retrospective search of the patient and pathologic databases of Mayo Clinic in Rochester, MN, for patients with CNC and clinical or laboratory findings of CS. Thirty-seven patients with CNC were identified. Twenty-nine had clinical, pathologic, or laboratory evidence of an adrenocortical disorder. Seventeen had classic CS; 15 underwent bilateral, subtotal, or partial unilateral adrenalectomy, and 2 had no treatment. Pathologically, the glands were normal sized or slightly enlarged with multiple small (1 to 4 mm), brown, black, and yellow micronodules (primary pigmented nodular adrenocortical disease; PPNAD). Three glands each had a mass: a 2 cm adenoma, a 1.5 cm macronodule, and an unencapsulated 1.8 cm myelolipoma. Fourteen of the patients were alive at follow-up, and 3 were deceased; 2 of the latter had PPNAD at autopsy, and the third had PPNAD at surgery. Twelve patients without clinical features of classic CS had abnormal adrenocortical testing results; none developed classic CS during follow-up (mean, 10 y). Autopsy findings in 1 showed bilateral vacuolated cell cortical hyperplasia.

Celecoxib treatment of fibrous dysplasia (FD) in a human FD cell line and FD-like lesions in mice with protein kinase A (PKA) defects

Osteochondromyxomas (OMX) in the context of Carney complex (CNC) and fibrous dysplasia (FD)-like lesions (FDLL) in mice, as well as isolated myxomas in humans may be caused by inactivation of PRKAR1A, the gene coding for the type 1a regulatory subunit (R1α) of cAMP-dependent protein kinase (PKA). OMXs and FDLL in mice lacking Prkar1a grow from abnormal proliferation of adult bone stromal cells (aBSCs). Prkar1a and Prkaca (coding for Cα) haploinsufficiency leads to COX2 activation and prostaglandin E2 (PGE2) production that, in turn, activates proliferation of aBSCs. Celecoxib is a cyclooxygenase-2 (COX2) inhibitor. We hypothesized that COX-2 inhibition may have an effect in FD and FDLL. In vitro treatment of a human cell line prepared from a FD patient with Celecoxib resulted in decreased PGE2 and cell proliferation. Treatment of mice haploinsufficient for R1α and Cα with 1500 mg/kg Celecoxib led to decreased PGE2 and proliferation and increased apoptosis, with a corresponding gene expression profile, resulting in dramatic reduction of tumor growth. Furthermore, the treatment improved the organization of cortical bone that was adjacent to the tumor. We conclude that, in vitro and in vivo, Celecoxib had an inhibitory effect on FD cell proliferation and in mouse FDLL structure, respectively. We speculate that COX-2 inhibitors offer an attractive alternative to current treatments for benign tumors such as OMX and FD that, apart from tumor suppression, may mechanically stabilize affected bones.

RANKL blockade prevents and treats aggressive osteosarcomas

Osteosarcoma (OS) is the most common primary bone cancer, which occurs primarily in children and adolescents, severely affecting survivors' quality of life. Despite its chemosensitivity and treatment advances, long-term survival rates for OS patients have stagnated over the last 20 years. Thus, it is necessary to develop new molecularly targeted therapies for this metastatic bone cancer. Mutations in TP53 and RB are linked to OS predisposition and to the evolution of spontaneous OS. We established receptor activator of nuclear factor κB ligand (RANKL) as a therapeutic target for suppression and prevention of OS. Combined conditional osteoblast-specific deletions of Rb, p53, and the protein kinase A (PKA) regulatory subunit Prkar1α genes in genetically engineered mouse models (GEMMs) generate aggressive osteosarcomas, characterized by PKA, RANKL, and osteoclast hyperactivity. Whole-body Rankl deletion completely abrogates tumorigenesis. Although osteoblastic Rank deletion has little effect, osteoclastic Rank deletion delays tumorigenesis and prolongs life span. The latter is associated with inactivation of osteoclastogenesis and up-regulation of the tumor suppressor phosphatase and tensin homolog (PTEN). Further, we use these GEMMs as preclinical platforms to show that RANKL blockade with RANK-Fc arrests tumor progression and improves survival and also inhibits lung metastasis. Moreover, preemptive administration of RANK-Fc completely prevents tumorigenesis in mice highly predisposed to this aggressive cancer. Denosumab, a fully human monoclonal antibody against RANKL, is currently used to treat patients with osteoporosis or bone metastases. Our studies provide a strong rationale to consider RANKL blockade for the treatment and prevention of aggressive RANKL-overexpressing OS in humans.

Refinements in Sarcoma Classification in the Current 2013 World Health Organization Classification of Tumours of Soft Tissue and Bone

The fourth edition of the World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone was published in February 2013. The 2013 WHO volume provides an updated classification scheme and reproducible diagnostic criteria, which are based on recent clinicopathologic studies and genetic and molecular data that facilitated refined definition of established tumor types, recognition of novel entities, and the development of novel diagnostic markers. This article reviews updates and changes in the classification of bone and soft tissue tumors from the 2002 volume.

Osteochondromyxoma: Review of a rare carney complex criterion

Osteochondromyxoma is an extremely rare bone tumor associated with 1% of Carney complex patients and constitutes one of its 11 diagnostic criteria. This narrative review of osteochondromyxoma is based on a search of all references to the topic in PubMed, Web Of Science, SCOPUS, ScienceDirect, and JSTOR databases. Special attention was focused on case reports, leading to a review encompassing the case reports to date, as well as related animal model studies. This review covers the current understanding of osteochondromyxoma, highlighting its variability while providing consensus on the most common clinical presentation, pathological findings, and genetic features of this rare bone tumor.

Multiple osteoblastomas in a child with Cushing syndrome due to bilateral adrenal micronodular hyperplasias

Adrenocorticotropin-independent adrenal hyperplasias are rare diseases, which are classified into macronodular (>1 cm) and micronodular (≤1 cm) hyperplasia. Micronodular adrenal hyperplasia is subdivided into primary pigmented adrenocortical disease and a limited or nonpigmented form 'micronodular adrenocortical disease (MAD)', although considerable morphological and genetic overlap is observed between the 2 groups. We present an unusual case of a 44-month-old girl who was diagnosed with Cushing syndrome due to MAD. She had presented with spotty pigmentation on her oral mucosa, lips and conjunctivae and was diagnosed with multiple bone tumors in her femur, pelvis and skull base at the age of 8 years. Her bone tumor biopsies were compatible with osteoblastoma. This case highlights the importance of verifying the clinicopathologic correlation in Cushing syndrome and careful follow-up and screening for associated diseases.

Hematopoietic neoplasms in Prkar2a-deficient mice

Background

Protein kinase A (PKA) is a holoenzyme that consists of a dimer of regulatory subunits and two inactive catalytic subunits that bind to the regulatory subunit dimer. Four regulatory subunits (RIα, RIβ, RIIα, RIIβ) and four catalytic subunits (Cα, Cβ, Cγ, Prkx) have been described in the human and mouse genomes. Previous studies showed that complete inactivation of the Prkar1a subunit (coding for RIα) in the germline leads to embryonic lethality, while Prkar1a–deficient mice are viable and develop schwannomas, thyroid, and bone neoplasms, and rarely lymphomas and sarcomas. Mice with inactivation of the Prkar2a and Prkar2b genes (coding for RIIα and RIIβ, respectively) are also viable but have not been studied for their susceptibility to any tumors.

Methods

Cohorts of Prkar1a^+/−, Prkar2a^+/−, Prkar2a^−/−, Prkar2b^+/− and wild type (WT) mice have been observed between 5 and 25 months of age for the development of hematologic malignancies. Tissues were studied by immunohistochemistry; tumor-specific markers were also used as indicated. Cell sorting and protein studies were also performed.

Results

Both Prkar2a^−/− and Prkar2a^+/− mice frequently developed hematopoietic neoplasms dominated by histiocytic sarcomas (HS) with rare diffuse large B cell lymphomas (DLBCL). Southern blot analysis confirmed that the tumors diagnosed histologically as DLBCL were clonal B cell neoplasms. Mice with other genotypes did not develop a significant number of similar neoplasms.

Conclusions

Prkar2a deficiency predisposes to hematopoietic malignancies in vivo. RIIα’s likely association with HS and DLBCL was hitherto unrecognized and may lead to better understanding of these rare neoplasms.

Paediatric chondrosarcomas: a retrospective review of 17 cases

AIMS

Chondrosarcoma is primarily a tumour of adulthood and old age. Some studies indicate that survival is worse in paediatric than in adult chondrosarcomas. In view of the rarity of paediatric chondrosarcoma, few large studies are currently available.

METHODS AND RESULTS

We evaluated the clinical, radiological and pathological features of a single institution series of chondrosarcomas presenting in patients younger than 17 years between 1981 and 2014. Seventeen patients with central (10), peripheral (five) and periosteal (two) chondrosarcoma were retrieved. The patients received various treatments according to the dimension, stage and grading of the lesions. Only two tumours, treated with resection, recurred after the first diagnosis, at 11 and 108 months, respectively. All patients but one were alive without disease at the time of the last follow-up (median: 148 months). The one patient who died of disease 27 months after diagnosis had a grade 2 central chondrosarcoma of the metacarpal bone. He was affected by Maffucci syndrome and developed multiple bone and lung metastases.

CONCLUSIONS

Chondrosarcoma in children is rare but does exist, and is not limited to the head and neck region. Our findings do not support the current view that chondrosarcomas are more aggressive in children than in adults.

Celecoxib reduces glucocorticoids in vitro and in a mouse model with adrenocortical hyperplasia

Primary pigmented nodular adrenocortical disease (PPNAD), whether in the context of Carney complex (CNC) or isolated, leads to ACTH-independent Cushing's syndrome (CS). CNC and PPNAD are caused typically by inactivating mutations of PRKAR1A, a gene coding for the type 1a regulatory subunit (R1α) of cAMP-dependent protein kinase (PKA). Mice lacking Prkar1a, specifically in the adrenal cortex (AdKO) developed CS caused by bilateral adrenal hyperplasia (BAH), which is formed from the abnormal proliferation of fetal-like adrenocortical cells. Celecoxib is a cyclooxygenase 2 (COX2) inhibitor. In bone, Prkar1a inhibition is associated with COX2 activation and prostaglandin E2 (PGE2) production that, in turn, activates proliferation of bone stromal cells. We hypothesized that COX2 inhibition may have an effect in PPNAD. In vitro treatment of human cell lines, including one from a patient with PPNAD, with celecoxib resulted in decreased cell viability. We then treated AdKO and control mice with 1500 mg/kg celecoxib or vehicle. Celecoxib treatment led to decreased PGE2 and corticosterone levels, reduced proliferation and increased apoptosis of adrenocortical cells, and decreased steroidogenic gene expression. We conclude that, in vitro and in vivo, celecoxib led to decreased steroidogenesis. In a mouse model of PPNAD, celecoxib caused histological changes that, at least in part, reversed BAH and this was associated with a reduction of corticosterone levels.

Medical and Surgical Management of Carney Complex

Carney complex is a rare, autosomal dominant genetic disorder that consists of multiple myxomatous lesions and endocrine abnormalities, including skin lesions, cardiac myxomas, primary pigmented nodular adrenocortical disease, and acromegaly. This review discusses the medical and surgical treatment of patients with Carney complex.

Sarcoma classification: an update based on the 2013 World Health Organization Classification of Tumors of Soft Tissue and Bone

The 2013 World Health Organization Classification of Tumors of Soft Tissue and Bone incorporates changes in tumor classification, as well as new genetic insights into the pathogenesis of many different tumor types that have emerged over the 11 years since the publication of the prior volume. This article reviews changes in the classification of soft tissue and bone sarcomas as well as tumors of intermediate biologic potential in the 2013 World Health Organization volume, new molecular insights into these tumors, and associated surgical and clinical implications.

Knockdown of PRKAR1A, the gene responsible for Carney complex, interferes with differentiation in osteoblastic cells

PRKAR1A is the gene encoding the type 1A regulatory subunit of protein kinase A, and it is the cause of the inherited human tumor syndrome Carney complex. Data from our laboratory has demonstrated that Prkar1a loss causes tumors in multiple cell lineages, including neural crest cells and osteoblasts. We have proposed that one mechanism by which tumorigenesis occurs is through the failure of terminal differentiation. In the present study, we directly test the effects of Prkar1a reduction on osteogenic differentiation in mouse and human cells in vitro. We found that Prkar1a levels noticeably increased during osteoblastic differentiation, indicating a positive correlation between the expression of Prkar1a and osteogenic potential. To validate this hypothesis, we generated stable Prkar1a knockdown in both mouse and human cells. These cells displayed significantly suppressed bone nodule formation and decreased expression of osteoblast markers such as osteocalcin and osteopontin. These observations imply that the antiosteogenic effect of Prkar1a ablation is not species or cell line specific. Furthermore, because Runt-related transcription factor-2 (Runx2) is a key mediator of osteoblast differentiation, we reasoned that the function of this transcription factor may be inhibited by Prkar1a knockdown. Chromatin immunoprecipitation and luciferase assays demonstrated that Prkar1a ablation repressed DNA binding and function of Runx2 at its target genes. Additionally, we determined that this effect is likely due to reductions in the Runx2-cooperating transcription factors forkhead box O1 and activating transcription factor 4. Taken together, this study provides direct evidence that ablation of Prkar1a interferes with signaling pathways necessary for osteoblast differentiation.

The complex of myxomas, spotty skin pigmentation and endocrine overactivity (Carney complex): imaging findings with clinical and pathological correlation

The complex of myxomas, spotty skin pigmentation and endocrine overactivity, or Carney complex (CNC), is a familial multiple endocrine neoplasia and lentiginosis syndrome. CNC is inherited in an autosomal dominant manner and is genetically heterogeneous. Its features overlap those of McCune-Albright syndrome and other multiple endocrine neoplasia (MEN) syndromes. Spotty skin pigmentation is the major clinical manifestation of the syndrome, followed by multicentric heart myxomas, which occur at a young age and are the lethal component of the disease. Myxomas may also occur on the skin (eyelid, external ear canal and nipple) and the breast. Breast myxomas, when present, are multiple and bilateral among female CNC patients, an entity which is also described as “breast-myxomatosis” and is a characteristic feature of the syndrome. Affected CNC patients often have tumours of two or more endocrine glands, including primary pigmented nodular adrenocortical disease (PPNAD), an adrenocorticotropin hormone (ACTH)-independent cause of Cushing’s syndrome, growth hormone (GH)-secreting and prolactin (PRL)-secreting pituitary adenomas, thyroid adenomas or carcinomas, testicular neoplasms (large-cell calcifying Sertoli cell tumours [LCCSCT]) and ovarian lesions (cysts and cancinomas). Additional infrequent but characteristic manifestations of CNC are psammomatous melanotic schwannomas (PMS), breast ductal adenomas (DAs) with tubular features, and osteochondromyxomas or “Carney bone tumour”.

Teaching Points

• Almost 60 % of the known CNC kindreds have a germline inactivating mutations in the PRKAR1A gene.

• Spotty skin pigmentation is the major clinical manifestation of CNC, followed by heart myxomas.

• Indicative imaging signs of PPNAD are contour abnormality and hypodense spots within the gland.

• Two breast tumours may present in CNC: myxoid fibroadenomas (breast myxomatosis) and ductal adenomas.

• Additional findings of CNC are psammomatous melanotic schwannomas (PMSs) and osteochondromyxomas.

Translocation t(12;17)(q24.1;q21) as the sole anomaly in a nasal chondromesenchymal hamartoma arising in a patient with pleuropulmonary blastoma

The identification of recurrent chromosomal abnormalities in benign and malignant mesenchymal neoplasms has provided important pathogenetic insight as well as powerful diagnostic adjuncts. Nasal chondromesenchymal hamartoma (NCMH), an extremely rare benign tumor arising in the sinonasal tract of infants and children, has not been previously subjected to cytogenetic analysis. Histopathologically composed of mixed mesenchymal elements, NCMH exhibits a relatively wide differential diagnosis to include chondromyxoid fibroma, chondroblastoma, aneurysmal bone cyst, fibrous dysplasia, and osteochondromyxoma. An interesting association with pleuropulmonary blastoma has been reported in a small subset of NCMH patients. In the current study, cytogenetic analysis of a NCMH arising in an 11-year-old boy with a past medical history of pleuropulmonary blastoma revealed a novel 12;17 translocation, t(12;17)(q24.1;q21), as the sole anomaly.

The transcriptome that mediates increased cyclic adenosine monophosphate signaling in PRKAR1A defects and other settings

OBJECTIVE

To review current knowledge on the involvement of cyclic adenosine monophosphate (cAMP) and interacting signaling pathways in predisposition to tumor formation in primary pigmented nodular adrenocortical disease (PPNAD), a type of bilateral adrenal hyperplasia (BAH) related to the multiple endocrine neoplasia Carney complex, and also in isolated PPNAD and other BAHs.

METHODS

We review the pertinent literature and discuss genetic defects associated with various endocrine and nonendocrine tumors.

RESULTS

A decade ago, we discovered that PPNAD and the Carney complex are caused by PRKAR1A mutations. PRKAR1A encodes the protein kinase A (PKA) regulatory subunit type IA, an important regulator of cAMP signaling in most cells. Recently, we described PKA or PRKAR1A abnormalities in a variety of other BAHs; in some of these cases, mutations in additional genes of the cAMP signaling pathway, the phosphodiesterases, were identified. Transcriptomic analyses of human lesions or animal models showed that abnormal cAMP/PKA signaling in the adrenal glands, and also in other tissues such as bone, leads to proliferation of tissue-specific pluripotential cells through activation of Wnt signaling.

CONCLUSION

Recent findings indicate the relevance of cAMP signaling in the pathogenesis of adrenocortical disease and point to the Wnt signaling pathway as a potential important mediator of tumorigenesis related to increased cAMP or PKA signaling (or both).

Virilizing ovarian stromal tumor in a young woman with Carney complex

A woman with Carney complex presented at the age of 22 years with abdominal pain and hirsutism. As a baby, she had undergone excision of a right eyelid lesion, and at age 14 years she had undergone removal of a left lower eyelid nodule that subsequently recurred. Investigation revealed an elevated level of serum testosterone and a 2-cm left ovarian tumor. A left salpingo-oophorectomy was performed. Postoperatively, she experienced relief from abdominal pain, the serum level of testosterone normalized, and the hirsutism ameliorated. The tumor featured sheets of eosinophilic cells with lipochrome pigment, myeloid metaplasia, stromal metaplasia, and markedly abnormal blood vessels. Immunocytochemically, the tumor cells were positive for vimentin, synaptophysin, inhibin-A, and calrenin. Because of the clinical setting in which the neoplasm occurred, it is likely that is occurrence was related to Carney complex.

Recurrent PRKAR1A mutation in acrodysostosis with hormone resistance

The skeletal dysplasia characteristic of acrodysostosis resembles the Albright's hereditary osteodystrophy seen in patients with pseudohypoparathyroidism type 1a, but defects in the α-stimulatory subunit of the G-protein (GNAS), the cause of pseudohypoparathyroidism type 1a, are not present in patients with acrodysostosis. We report a germ-line mutation in the gene encoding PRKAR1A, the cyclic AMP (cAMP)-dependent regulatory subunit of protein kinase A, in three unrelated patients with acrodysostosis and resistance to multiple hormones. The mutated subunit impairs the protein kinase A response to stimulation by cAMP; this explains our patients' hormone resistance and the similarities of their skeletal abnormalities with those observed in patients with pseudohypoparathyroidism type 1a.

How does cAMP/protein kinase A signaling lead to tumors in the adrenal cortex and other tissues?

The overwhelming majority of benign lesions of the adrenal cortex leading to Cushing syndrome are linked to one or another abnormality of the cAMP signaling pathway. A small number of both massive macronodular adrenocortical disease and cortisol-producing adenomas harbor somatic GNAS mutations. Micronodular adrenocortical hyperplasias are either pigmented (the classic form being that of primary pigmented nodular adrenocortical disease) or non-pigmented; micronodular adrenocortical hyperplasias can be seen in the context of other conditions or isolated; for example, primary pigmented nodular adrenocortical disease usually occurs in the context of Carney complex, but isolated primary pigmented nodular adrenocortical disease has also been described. Both Carney complex and isolated primary pigmented nodular adrenocortical disease are caused by germline PRKAR1A mutations; somatic mutations of this gene that regulates cAMP-dependent protein kinase are also found in cortisol-producing adenomas, and abnormalities of PKA are present in most cases of massive macronodular adrenocortical disease. Micronodular adrenocortical hyperplasias and some cortisol-producing adenomas are associated with phosphodiesterase 11A and 8B defects, coded, respectively, by the PDE11A and PDE8B genes. Mouse models of Prkar1a deficiency also show that increased cAMP signaling leads to tumors in adrenal cortex and other tissues. In this review, we summarize all recent data from ours and other laboratories, supporting the view that Wnt-signaling acts as an important mediator of tumorigenicity induced by abnormal PRKAR1A function and aberrant cAMP signaling.

Carney Complex: case report and review

Carney complex is a very rare multiple neoplasia syndrome with cardiac, cutaneous, and neural tumours with a variety of pigmented lesion of skin. We are reporting a rare case of carney complex in which left atrial myxoma with superficial angiomyxoma, giant cell tumour of bone and lentigines showed a unique association. This patient underwent successful surgical excision of left atrial myxoma under cardiopulmonary bypass.

Bone metastasis of glandular cardiac myxoma mimicking a metastatic carcinoma

Skeletal metastasis from a cardiac myxoma is rare. We describe an extremely unusual case of a cardiac myxoma metastasing to the femur in a 46-year-old female presenting with pain in the right hip. Radiographs showed an expansile lytic lesion with pathological fracture involving the neck and proximal shaft of the right femur. Histology revealed features of cardiac myxoma with heterologous glandular elements, which was initially mistaken for a metastatic mucin-secreting adenocarcinoma.

Protein kinase A regulates caspase-1 via Ets-1 in bone stromal cell-derived lesions: a link between cyclic AMP and pro-inflammatory pathways in osteoblast progenitors

Patients with genetic defects of the cyclic (c) adenosine-monophosphate (AMP)-signaling pathway and those with neonatal-onset multisystem inflammatory disease (NOMID) develop tumor-like lesions of the long bones. The molecular basis of this similarity is unknown. NOMID is caused by inappropriate caspase-1 activity, which in turn activates the inflammasome. The present study demonstrates that NOMID bone lesions are derived from the same osteoblast progenitor cells that form fibroblastoid tumors in mice and humans with defects that lead to increased cAMP-dependent protein kinase A (PKA) signaling. NOMID tumor cells showed high PKA activity, and an increase in their cAMP signaling led to PKA-specific activation of caspase-1. Increased PKA led to inflammation-independent activation of caspase-1 via over-expression of the proto-oncogene (and early osteoblast factor) Ets-1. In NOMID tumor cells, as in cells with defective PKA regulation, increased prostaglandin E2 (PGE2) led to increased cAMP levels and activation of Wnt signaling, like in other states of inappropriate PKA activity. Caspase-1 and PGE2 inhibition led to a decrease in cell proliferation of both NOMID and cells with abnormal PKA. These data reveal a previously unsuspected link between abnormal cAMP signaling and defective regulation of the inflammasome and suggest that caspase-1 and PGE2 inhibition may be therapeutic targets in bone lesions associated with defects of these two pathways.

Carney complex: Clinical and genetic 2010 update

First described in the mid 1980s, Carney complex is a rare dominantly heritable multiple endocrine neoplasia syndrome that affects endocrine glands as the adrenal cortex, the pituitary and the thyroid. It is associated with many other nonendocrine tumors, including cardiac myxomas, testicular tumors, melanotic schwannoma, breast myxomatosis, and abnormal pigmentation or myxomas of the skin. The Carney complex gene 1 was identified 10 years ago as the regulatory subunit 1A of protein kinase A (PRKAR1A) located at 17q22-24. An inactivating heterozygous germ line mutation of PRKAR1A is observed in about two-thirds of Carney complex patients. This last decade many progresses have been done in the knowledge of this rare disease and its genetics. This review outlines the current state of this knowledge on Carney complex.

Prkar1a is an osteosarcoma tumor suppressor that defines a molecular subclass in mice

Some cancers have been stratified into subclasses based on their unique involvement of specific signaling pathways. The mapping of human cancer genomes is revealing a vast number of somatic alterations; however, the identification of clinically relevant molecular tumor subclasses and their respective driver genes presents challenges. This information is key to developing more targeted and personalized cancer therapies. Here, we generate a new mouse model of genomically unstable osteosarcoma (OSA) that phenocopies the human disease. Integrative oncogenomics pinpointed cAMP-dependent protein kinase type I, alpha regulatory subunit (Prkar1a) gene deletions at 11qE1 as a recurrent genetic trait for a molecularly distinct subclass of mouse OSA featuring RANKL overexpression. Using mouse genetics, we established that Prkar1a is a bone tumor suppressor gene capable of directing subclass development and driving RANKL overexpression during OSA tumorigenesis. Finally, we uncovered evidence for a PRKAR1A-low subset of human OSA with distinct clinical behavior. Thus, tumor subclasses develop in mice and can potentially provide information toward the molecular stratification of human cancers.

Neural crest-specific loss of Prkar1a causes perinatal lethality resulting from defects in intramembranous ossification

The cranial neural crest (CNC) undergoes complex molecular and morphological changes during embryogenesis in order to form the vertebrate skull, and nearly three quarters of all birth defects result from defects in craniofacial development. The molecular events leading to CNC differentiation have been extensively studied; however, the role of the cAMP-dependent protein kinase [protein kinase A (PKA)] during craniofacial development has only been described in palate formation. Here, we provide evidence that strict PKA regulation in postmigratory CNC cells is essential during craniofacial bone development. Selective inactivation of Prkar1a, a regulatory subunit of the PKA holoenzyme, in the CNC results in perinatal lethality caused by dysmorphic craniofacial development and subsequent asphyxiation. Additionally, aberrant differentiation of CNC mesenchymal cells results in anomalous intramembranous ossification characterized by formation of cartilaginous islands in some areas and osteolysis of bony trabeculae with fibrous connective tissue stabilization in others. Genetic interaction studies revealed that genetic reduction of the PKA catalytic subunit C(alpha) was able to rescue the phenotype, whereas reduction in Cbeta had no effect. Overall, these observations provide evidence of the essential role of proper regulation of PKA during the ossification of the bones of the skull. This knowledge may have implications for the understanding and treatment of craniofacial birth defects.

Clinical and molecular genetics of Carney complex

Carney complex (CNC) is a rare multiple familial neoplasia syndrome that is characterized by multiple types of skin tumors and pigmented lesions, endocrine neoplasms, myxomas and schwannomas and is inherited in an autosomal dominant manner. Clinical and pathologic diagnostic criteria are well established. Over 100 pathogenic variants in the regulatory subunit type 1A (RI-A) of the cAMP-dependent protein kinase (PRKAR1A) have been detected in approximately 60% of CNC patients, most leading to R1A haploinsufficiency. Other CNC-causing genes remain to be identified. Recent studies provided some genotype-phenotype correlations in CNC patients carrying PRKAR1A-inactivating mutations, which provide useful information for genetic counseling and/or prognosis; however, CNC remains a disease with significant clinical heterogeneity. Recent mouse and in vitro studies have shed light into how R1A haploinsufficiency causes tumors. PRKAR1A defects appear to be weak tumorigenic signals for most tissues; Wnt signaling activation and cell cycle dysregulation appear to be important mediators of the tumorigenic effect of a defective R1A.

Alternate protein kinase A activity identifies a unique population of stromal cells in adult bone

A population of stromal cells that retains osteogenic capacity in adult bone (adult bone stromal cells or aBSCs) exists and is under intense investigation. Mice heterozygous for a null allele of prkar1a (Prkar1a(+/-)), the primary receptor for cyclic adenosine monophosphate (cAMP) and regulator of protein kinase A (PKA) activity, developed bone lesions that were derived from cAMP-responsive osteogenic cells and resembled fibrous dysplasia (FD). Prkar1a(+/-) mice were crossed with mice that were heterozygous for catalytic subunit Calpha (Prkaca(+/-)), the main PKA activity-mediating molecule, to generate a mouse model with double heterozygosity for prkar1a and prkaca (Prkar1a(+/-)Prkaca(+/-)). Unexpectedly, Prkar1a(+/-)Prkaca(+/-) mice developed a greater number of osseous lesions starting at 3 months of age that varied from the rare chondromas in the long bones and the ubiquitous osteochondrodysplasia of vertebral bodies to the occasional sarcoma in older animals. Cells from these lesions originated from an area proximal to the growth plate, expressed osteogenic cell markers, and showed higher PKA activity that was mostly type II (PKA-II) mediated by an alternate pattern of catalytic subunit expression. Gene expression profiling confirmed a preosteoblastic nature for these cells but also showed a signature that was indicative of mesenchymal-to-epithelial transition and increased Wnt signaling. These studies show that a specific subpopulation of aBSCs can be stimulated in adult bone by alternate PKA and catalytic subunit activity; abnormal proliferation of these cells leads to skeletal lesions that have similarities to human FD and bone tumors.

Divergent myoid, neuroendocrine, and perineural differentiation in a nasal tumor of a patient with Carney complex

A 39-year-old woman with Carney complex presented with a stroke of undetermined etiology. Computed tomography showed bilateral thalamic infarctions and also an unsuspected multicompartmental cystic neoplasm that had eroded the anterior clivus and extended forward into the nasopharynx. Histologically, the mass appeared benign and was composed of spindle cells and multiple foci of striated muscle. Immunohistochemically, the spindle cells were strongly reactive for S-100 protein and to a lesser extent for CD57, collagen IV, neuron-specific enolase, smooth muscle actin, epithelial membrane antigen, and glut-1. The striated muscle cells were positive for desmin and myogenin. The MIB-1 labeling index was 0.5%. Ultrastructural examination was necessary to reveal the full extent of divergent differentiation. Ultrastructurally, the spindle cells showed divergent differentiation along several cell lines, including smooth muscle, neuroendocrine, hybrid smooth muscle-neuroendocrine, perineural-like cells, and striated muscle. The occurrence of this unique lesion in a patient with the Carney complex raises the possibility that it may be a rare component of the syndrome.

[Carney complex. Clinical, pathological and genetic features in two generations of a family]

Clinical symptoms of Carney complex occurred in two female members of one family (mother and daughter). In addition to the clinical symptoms, we describe the pathological findings in the adrenals (pigmented nodular hyperplasia of the adrenal cortex), heart (myxoma) and skin/soft tissues (superficial angiomyxomas). Genetic investigation revealed a mutation on the long arm of chromosome 17 in both patients; this mutation had previously been described only in Carney complex type 1. Unilateral adrenalectomy was performed in both these cases, 13 years ago and 7 months ago, respectively. Lifelong cardiac surveillance is mandatory to prevent death from embolism or arrhythmia.

Mutation of Prkar1a causes osteoblast neoplasia driven by dysregulation of protein kinase A

Carney complex (CNC) is an autosomal dominant neoplasia syndrome caused by inactivating mutations in PRKAR1A, the gene encoding the type 1A regulatory subunit of protein kinase A (PKA). This genetic defect induces skin pigmentation, endocrine tumors, myxomas, and schwannomas. Some patients with the complex also develop myxoid bone tumors termed osteochondromyxomas. To study the link between the PRKAR1A mutations and tumor formation, we generated a mouse model of this condition. Prkar1a(+/-) mice develop bone tumors with high frequency, although these lesions have not yet been characterized, either from human patients or from mice. Bone tumors from Prkar1a(+/-) mice were heterogeneous, including elements of myxomatous, cartilaginous, and bony differentiation that effaced the normal bone architecture. Immunohistochemical analysis identified an osteoblastic origin for the abnormal cells associated with islands of bone. To better understand these cells at the biochemical level, we isolated primary cultures of tumoral bone and compared them with cultures of bone from wild-type animals. The tumor cells exhibited the expected decrease in Prkar1a protein and exhibited increased PKA activity. At the phenotypic level, we observed that tumor cells behaved as incompletely differentiated osteoblasts and were able to form tumors in immunocompromised mice. Examination of gene expression revealed down-regulation of markers of bone differentiation and increased expression of locally acting growth factors, including members of the Wnt signaling pathway. Tumor cells exhibited enhanced growth in response to PKA-stimulating agents, suggesting that tumorigenesis in osteoblast precursor cells is driven by effects directly mediated by the dysregulation of PKA.

A mouse model for the Carney complex tumor syndrome develops neoplasia in cyclic AMP-responsive tissues

Carney complex is an autosomal dominant neoplasia syndrome characterized by spotty skin pigmentation, myxomatosis, endocrine tumors, and schwannomas. This condition may be caused by inactivating mutations in PRKAR1A, the gene encoding the type 1A regulatory subunit of protein kinase A. To better understand the mechanism by which PRKAR1A mutations cause disease, we have developed conventional and conditional null alleles for Prkar1a in the mouse. Prkar1a(+/-) mice developed nonpigmented schwannomas and fibro-osseous bone lesions beginning at approximately 6 months of age. Although genotype-specific cardiac and adrenal lesions were not seen, benign and malignant thyroid neoplasias were observed in older mice. This spectrum of tumors overlaps that seen in Carney complex patients, confirming the validity of this mouse model. Genetic analysis indicated that allelic loss occurred in a subset of tumor cells, suggesting that complete loss of Prkar1a plays a key role in tumorigenesis. Similarly, tissue-specific ablation of Prkar1a from a subset of facial neural crest cells caused the formation of schwannomas with divergent differentiation. These observations confirm the identity of PRKAR1A as a tumor suppressor gene with specific importance to cyclic AMP-responsive tissues and suggest that these mice may be valuable tools not only for understanding endocrine tumorigenesis but also for understanding inherited predispositions for schwannoma formation.