Multicystic Encephalomalacia: The Neuropathology of Systemic Neonatal Parechovirus Infection.

The Neuropathology of Human Parechovirus (HPeV) is not widely described due to the relatively recent discovery of the virus combined with a limited number of autopsy case reports. We report the case of an infant boy born at 38 weeks who, six days after birth, presented with fever and severe neurological dysfunction. Human Parechovirus Type 3 (HPeV3) RNA was detected in his cerebrospinal fluid (CSF) and blood. He died five days after his initial presentation. Neuropathologic examination demonstrated multicystic encephalomalacia (ME). This case report confirms that white matter pathology is dominant in HPeV3 infection. A unique feature, of HPeV encephalomalacia is absence of CSF pleocytosis and minimal inflammation in the meninges. The findings permit comment on the pathogenesis of brain injury by this virus.

Proliferative, reparative, and reactive benign bone lesions that may be confused diagnostically with true osseous neoplasms.

Diagnostic problems attending intraosseous and parosteal pseudoneoplastic lesions can be radiographic, or histological, or both. Proliferations in this category may contain cellular fibro-osseous or chondro-osseous tissues that are difficult to separate microscopically from those seen in various true neoplasms of the bones. This review considers the clinicopathologic features of fibrous dysplasia, benign fibro-osseous lesions of the jawbones, osteofibrous dysplasia, metaphyseal fibrous defect, giant-cell reparative granuloma, "brown tumor" of hyperparathyroidism, synovial chondrometaplasia, aneurysmal bone cyst, tumefactive chronic osteomyelitis, proliferative Paget disease, and polyvinylpyrrolidone storage disease of bone.

Mediastinal and neck kaposiform hemangioendothelioma: report of three cases.

Kaposiform hemangioendothelioma is an aggressive vascular tumor, named for its striking histologic resemblance to Kaposi sarcoma and locally invasive growth. Mortality is high, and ranges from 10% to 24% for all kaposiform hemangioendothelioma lesions, with a significantly higher mortality for deep soft-tissue or visceral lesions occurring in infants less than 6 months. Mediastinal and neck kaposiform hemangioendothelioma in particular merit special discussion, as involvement of these critical anatomic locations results in significant site-specific therapeutic challenges due to invasion of vital structures, inherent delays in establishing histopathologic confirmation, and difficulties in monitoring disease status. We report our experience with three cases of mediastinal and neck kaposiform hemangioendothelioma, emphasizing the unique diagnostic and management challenges, variable response to treatment and outcome of this anatomic variant of kaposiform hemangioendothelioma.

Tumor progression in DICER1-mutated cystic nephroma-witnessing the genesis of anaplastic sarcoma of the kidney.

We report a 7-month-old female infant with a multicystic left renal tumor having histologic features predominantly of a cystic nephroma, but with microscopic cellular foci which contained atypical mitotic figures and anaplastic nuclei. Immunohistochemistry showed strong p53 reactivity in the anaplastic region. DICER1 sequencing confirmed 2 mutations: germ line mutation c.2450delC and c.5438A>G somatic within the tumor. Despite an initial consideration of cystic partially differentiated nephroblastoma, the presence of anaplasia ruled that possibility out, as this is not an acceptable feature for that diagnosis. Moreover, the germ line DICER1 mutation prompted consideration that this case represents a unique "nascent" anaplastic sarcoma of kidney, and further immunohistochemical workup demonstrated cytoplasmic, but no nuclear WT-1 reactivity in the cellular foci. The importance of meticulous sampling of cystic lesions is highlighted by this unprecedented case, which lends support to the recent recognition of anaplastic sarcoma of kidney as a DICER1-associated cancer.

Gonadoblastoma in patients with 45,X/46,XY mosaicism: A 16-year experience.

BACKGROUND: It is recognised that individuals with a 45,X/46,XY karyotype, known as Turner mosaic syndrome with Y chromosome material (TMSY), have an increased risk of developing gonadoblastoma (GB), which may then devolve into one of a number of germ cell malignancies. Hence, children with TMSY are usually recommended to undergo prophylactic gonadectomy. OBJECTIVE: We designed this study to describe the phenotypic features of our series of children with TMSY who underwent prophylactic gonadectomy in order to evaluate the prevalence of GB and germ cell malignancies in their resected specimens. STUDY DESIGN: This is a retrospective case series wherein we comprehensively reviewed the clinical, histological, and cytogenetic features of all patients who underwent prophylactic gonadectomy at three tertiary paediatric referral centres over 16 years. Cases were identified from surgical logbooks and through the institutional histopathology database. Data were collected with particular reference to clinical phenotype, predominant karyotype cell line, operative management, anatomical findings and the presence of neoplastic changes. RESULTS: Fourteen children ranging in age at the time of surgery from 2 weeks to 17 years were included in the series. Eleven children were reared as females. The three children who were reared as males had severe penoscrotal hypospadias. The 46,XY cell line was the predominant cell line in seven (50%) cases in blood lymphocytes. The resected specimens from four patients (28.6%) contained GB, with three patients having bilateral GB. This sub-group of patients with GB were aged 5 months, 48 months, 71 months, and 13 years. GB arose in one patient with and three patients without genital virilisation. There was no focus of invasive germ cell tumour in any specimen. DISCUSSION: GB may be present in infants with TMSY as young as 5 months, even with low levels of Y chromosome material. The prevalence of GB in prophylactic gonadectomy specimens is similar to many previously reported series, although the absence of dysgerminoma in our series is reassuring. The exclusive presence of GB in intra-abdominal gonads is in keeping with the findings of several other series. CONCLUSION: Owing to the presence of gonadoblastoma in the gonads of children with TMSY as young as 5 months, we recommend that all patients with intra-abdominal gonads in the context of TMSY should duly undergo prophylactic gonadectomy, although the timing of such surgery can be discussed with parents during counselling regarding the risk of malignancy.

Primary desmoplastic small round cell tumor of bone: report of a case with cytogenetic confirmation.

We report a case of desmoplastic small round cell tumor occurring in the right ilium of a 13-year-old boy. Morphologically, the neoplasm consisted of small round cells of primitive appearance with a diffuse growth pattern replacing marrow space and eroding bone. Immunohistochemical staining was positive for vimentin, synapsin, CD99 (MIC2 protein), and FLI-1, prompting an initial diagnosis of Ewing sarcoma/primitive neuroectodermal tumor. However, a diagnosis of desmoplastic small round cell tumor was rendered after the detection by cytogenetic analysis of the reciprocal chromosomal translocation, t(11;22)(p13;q12), which is uniquely associated with this tumor. This is the first documented instance of desmoplastic small round cell tumor arising in bone.

Nasal chondromesenchymal hamartoma in children with pleuropulmonary blastoma--A report from the International Pleuropulmonary Blastoma Registry registry.

OBJECTIVES: Nasal chondromesenchymal hamartoma (NCMH) is an uncommon chondro-stromal tumor of the nasal cavity and paranasal sinuses in infancy and childhood. Pleuropulmonary blastoma (PPB) is also a rare malignancy of lung and pleura in childhood and is the sentinel disease of an important familial tumor and dysplasia syndrome. This study identified NCMH in PPB patients. METHODS: The International PPB Registry collects cases of PPB using central pathology review and evaluation of clinical records. The Registry also evaluates PPB literature. Examples of NCMH occurring with PPB were identified. Clinical records, digital radiography and pathologic specimens of PPB-associated NCMH cases were analyzed. RESULTS: Among approximately 625 cases of PPB, four children developed NCMH. These cases are among 28 total reported NCMH cases. NCMH presented with sinonasal congestion and visible polypoid nasal masses and were diagnosed from ages 7 to 15 years, similar to older reported NCMH cases. NCMH involved the nasal cavity, paranasal sinuses and upper nasopharynx, was bilateral in three children and locally recurrent in one. In two children, NCMH had the characteristic pathologic spectrum of immature nodules of cartilage surrounded by spindle cell stroma, whereas the other two NCMH displayed mature chondroid nodules and a less varied fibrous stroma. NCMH was not identified in family members with PPB. CONCLUSIONS: NCMH developing in four children with PPB indicates that NCMH is part of the heredofamilial disease complex associated with PPB. Otorhinolaryngologists and pediatric oncologists should be aware that these two rare conditions occur together and that affected patients may have a familial predisposition to childhood malignant and dysplastic disease.

Heat-accelerated fixation and rapid dissection of the pediatric brain at autopsy: a pragmatic approach to the difficulties of organ retention.

We investigated whether it is possible to accelerate the examination of a pediatric brain at autopsy and thus facilitate its return to the body before a funeral without compromising the quality of the neuropathologic examination. Accelerated fixation and next-day dissection of the brain was performed in selected cases over a 2-year period by using a microwave histologic tissue processor (MicroMed T/T MEGA, Milestone, Sorisole, Italy). Direct comparison of the histologic appearance and immunohistochemical reactivity of 2 cases, 1 fixed by conventional methods and 1 fixed with the accelerated method, was performed in a blinded fashion by a specialist neuropathologist. Examination of rapidly fixed brain by conventional thin coronal sections was readily achieved. There was no appreciable difference between tissue sections stained with hematoxylin and eosin and prepared from conventional formalin-fixed cortical and cerebellar brain tissue and that fixed by rapid heat acceleration. Immunocytochemical studies were not adversely affected by the accelerated heat-fixation process of tissue. Heat-accelerated fixation is a potential method of speeding up the examination of the brain at autopsy without unduly compromising the quality of the neuropathologic examination.

Multifocal infantile myofibromatosis and generalized fibromuscular dysplasia in a child: evidence for a common pathologic process?

Infantile myofibromatosis (IM) is a condition characterized by the formation of spindle cell tumors of skin, soft tissue, and viscera. Although small vessel involvement by the process is a frequently identified and indeed diagnostically useful histological finding, involvement of large vessels is not widely reported. Fibromuscular dysplasia (FMD) is a noninflammatory arteriopathy characterized by intimal, medial, and/or adventitial fibroplasias leading to luminal compromise and aneurysm formation. Although venous disease has been reported, involvement of arterioles and viscera has not been identified. We report a patient in whom IM was diagnosed, on the basis of multiple soft tissue tumors present from birth, who subsequently developed generalized and ultimately fatal FMD. These two conditions exhibit overlapping pathologic features, including pronounced intimal fibroplasia. Their occurrence in a single individual may provide insights into the pathogenesis of both conditions, suggesting that they represent part of the same spectrum of vascular myofibroblastic proliferations.

Perianal rhabdomyosarcoma presenting as a perirectal abscess: A report of 11 cases.

BACKGROUND PURPOSE: The organs and soft tissues of the pelvis are some of the most common primary sites for rhabdomyosarcoma (RMS) in children and adolescents. In most cases a mass is detectable on clinical examination, and the initial concern is focused on the possibility of a neoplasm. The current report concerns 11 patients, each presented with a painful perineal-perianal mass suggesting an abscess to the extent that each one of these patients was treated initially with antibiotics or incision and drainage for several weeks to months before the pathologic diagnosis of RMS was established. METHODS: The authors reviewed the clinical histories of all patients with perirectal/perianal RMS from their respective institutions to identify cases in which the initial clinical diagnosis or impression was that of a perirectal abscess. Pathologic material was reviewed in all cases. RESULTS: Eleven patients, 7 of whom were girls, ranged in age from 1 to 16 years at diagnosis (median age, 14 years). Fever accompanied the clinical presentation in 2 patients. None of the patients had a past medical history of illness that may have predisposed them to a perirectal abscess, although one patient had a family history of inflammatory bowel disease. Duration of symptoms ranged from 1 month to 1 year (mean, 4.6 months). Each patient presented with a tender perianal/perineal nodule or mass. Inguinal adenopathy was present in 6 patients at diagnosis. White blood cell counts ranged from 6,600/mm(3) to 24,500/mm(3). LDH levels ranged from 414 to 3,432 U/L. The average time from presentation to pathologic diagnosis of RMS was 2.1 months. Nine of the 11 cases showed an alveolar pattern. All were high-stage disease. Of 7 patients with follow-up longer than 1 year, 2 (29%) are alive without disease. CONCLUSION: This report presents the need to consider the possibility of a malignant neoplasm, in this case RMS, in a child or adolescent with a putative perirectal abscess that fails to respond in the expected manner to incision and drainage and antibiotic therapy.