Jessica L. Davis

Syndrome-associated soft tissue tumours

Soft tissue neoplasms may be associated with a variety of genetic disorders and malformation syndromes, especially when they arise in children, adolescents and early adulthood. This review summarizes the principal histopathological types of soft tissue tumours which occur in various syndromes, with an emphasis on pathological features, genetic aspects and considerations for the diagnostic pathologist.

Special AT-rich sequence-binding protein 2 (SATB2) expression is sensitive but may not be specific for osteosarcoma as compared with other high-grade primary bone sarcomas.

The diagnosis of osteosarcoma, although important for eligibility in clinical trials and proper therapy, may be challenging when no bone or osteoid matrix is identified on biopsy. Therefore, other adjunct tests have been sought to help confirm the diagnosis. Special AT‐rich sequence‐binding protein 2 (SATB2) has been shown as a reliable marker of osteoblastic differentiation. The aim of this study was to examine SATB2 expression in osteosarcomas and other primary bone sarcomas, in order to evaluate its diagnostic utility in discriminating osteogenic from non‐osteogenic sarcomas.

Infantile NTRK-associated Mesenchymal Tumors:

Pediatric fibroblastic/myofibroblastic lesions are a relatively common group of tumors with varying morphologies, for which the molecular mechanisms are becoming increasingly well characterized. Congenital infantile fibrosarcoma (CIFS), perhaps the most well studied of these lesions is characterized by a recurrent ETV6-NTRK3 gene fusion. However, a notable subset of locally aggressive congenital/infantile soft tissue lesions with similar morphologic features to CIFS, have not to-date, shown evidence of any canonical molecular aberration. We describe 6 patients with mesenchymal tumors composed of infiltrative fibroblastic/myofibroblastic tumor cells and showing a morphologic spectrum of features much analogous to that previously described in CIFS but without ETV6 fusion transcripts. These tumors lacked a uniform immunoprofile, but showed variable expression of CD34, S100, smooth muscle actin, and CD30. All patients first developed a mass in infancy (≤2 months of age). Using next-generation DNA sequencing, TMP3-NTRK1 fusions were identified in 4 cases, an LMNA-NTRK1 fusion in one case, and a variant EML4-NTRK3 fusion in one case. Similar to infantile fibrosarcoma, these tumors were locally aggressive (with local recurrences if incompletely excised) and rarely metastasized (lung metastases in one patient). Proper identification of these tumors including investigation for NTRK family gene rearrangements is essential for diagnostic accuracy, as well as for clinical management decisions. Given the morbidity associated with radical resection of large soft tissue tumors, children with unresectable, recurrent, and/or metastatic disease may benefit from treatment with NTRK targeted therapies.

PAX2 expression in wilms tumors and other childhood neoplasms

PAX2 plays an important role in kidney development; although small studies have demonstrated PAX2 expression in Wilms tumors (WT), comprehensive studies on formalin-fixed tissue are lacking. Thus, we systematically evaluated PAX2 immunohistochemical staining in a retrospective study of pediatric WT, as compared with other pediatric tumors. We stained formalin-fixed, paraffin-embedded sections from 39 WT, 6 nephrogenic rests, 8 non-Wilms renal tumors, and 43 nonrenal pediatric small round cell tumors with 2 different PAX2 polyclonal antibodies. PAX2 demonstrated strong, diffuse staining of epithelial and blastema components of WT (97% of cases). PAX2 stained WT stroma in fewer cases (23%), but 80% of anaplastic foci were positive. Nephrogenic rests, 1 case of metanephric adenoma, and 1 pediatric renal cell carcinoma were also PAX2 positive; other pediatric renal tumors were negative. Neuroblastoma, primitive neuroectodermal tumor/Ewings, and T-cell acute lymphoblastic lymphoma (ALL) were PAX2 negative. However, PAX2 weakly stained some cases of B-cell ALL rhabdomyosarcoma (RMS) was also stained, especially alveolar RMS (83%), with less staining of embryonal RMS (13%). One of the antibodies also stained maturing myoid cytoplasm of WT and RMS. This study shows that PAX2 is a sensitive marker of WT (sensitivity 97%), but PAX2 shows weak-to-moderate-intensity nuclear staining of RMS and B-cell ALL, somewhat limiting its utility. However, PAX2 may be a helpful marker in certain diagnostic situations. We speculate that RMS and B-cell ALL staining could be due to antibody cross-reactivity with PAX family members with known expression in RMS and B-cell ALL.

Glomerular basement membrane lipidosis in Alagille syndrome

Alagille syndrome is characterized by a paucity of interlobular bile ducts with chronic cholestasis, cardiac, skeletal, and eye abnormalities and is associated predominantly with JAG1 mutations. Various renal abnormalities have been sporadically described. The classic renal histopathology described in Alagille syndrome is mesangiolipidosis, with lipid deposits predominately confined to the mesangium and minimal deposition within the glomerular basement membrane (GBM). We report a 5-year-old girl with Alagille syndrome who presented with persistent subnephrotic proteinuria and renal tubular acidosis. A renal biopsy showed GBM irregularities (mimicking membranous glomerulonephritis), mesangial sclerosis, and focal segmental glomerulosclerosis (FSGS) on light microscopy. Electron microscopy revealed few lipid inclusions within the mesangium but extensive inclusions along the GBM. These findings are mostly consistent with those reported previously in Alagille syndrome. However, the histologic distribution of lipid vacuoles is seemingly reversed in this patient and is uniquely accompanied by FSGS, emphasizing the spectrum of renal histopathology seen in Alagille syndrome. The proteinuria observed in this patient is likely attributed to significant GBM lipid deposition, which over time may contribute to the development of FSGS.

Management of central nervous system teratoma.

Central nervous system (CNS) teratomas are very rare neoplasms that contain tissues derived from all three germ cell layers (endoderm, mesoderm, and ectoderm). Patients with teratomas usually have a good prognosis. Given the paucity of cases in the literature, we present a retrospective review of 15 CNS teratomas treated over a 25 year period at the University of California, San Francisco. We describe the presentation, location, treatment, and adjuvant therapy for these patients, and highlight three unique cases that emphasize the diverse presentation and treatment of these rare tumors.

A young woman with systemic lupus erythematosus and extensive mesenteric vasculitis involving small and medium vessels

History of the present illness The patient had 2 recent hospital admissions. Two months prior to her current presentation, she presented to the emergency department with a tooth abscess for which she underwent incision and drainage, and received a 1-week course of penicillin. One week later, she was admitted with a fever of 40.8°C and was noted to have tooth decay on panoramic radiographs without evidence of an abscess. She was treated with intravenous vancomycin and piperacillin tazobactam for 48 hours and then switched to oral clindamycin. Because of her elevated international normalized ratio (INR), she was unable to undergo tooth extraction prior to discharge. Two weeks later, she was readmitted with 4 days of recurrent fevers, malaise, diffuse arthralgias, and increased dyspnea with minimal exertion. Previous lupus exacerbations were characterized by arthralgias, rash, and hemolytic anemia. On this admission, laboratory evaluation revealed leukocytosis, worsening anemia and thrombocytopenia, creatinine of 0.7 mg/dl, alkaline phosphatase of 127 units/liter (normal value 111), spot urine proteinto-creatinine ratio of 1.47 (prior 1.1), low C3 and C4, and an increase in her double-stranded DNA by enzyme immunoassay from 120 to 768 IU/ml (normal value 30). She was empirically treated with vancomycin and piperacillin tazobactam given her recent tooth infection. The elevated alkaline phosphatase level prompted an abdominal ultrasound that showed multiple small hypoechoic areas in the spleen. An extensive infectious evaluation, including blood cultures, fungal serologies, knee arthrocentesis, magnetic resonance imaging of the lumbar spine, transthoracic and transesophageal echocardiograms, and computed tomography of the chest, abdomen, and pelvis, was negative. Her viral serologies were also unremarkable, other than evidence of IgG seropositivity for cytomegalovirus (CMV) with a negative viral load, consistent with prior exposure. Despite broad-spectrum antibiotics, she remained febrile. Her baseline prednisone dose of 12.5 mg was increased to 60 mg daily for possible lupus flare, after which she defervesced within 48 hours. Her thrombocytopenia was thought to be secondary to SLE-related idiopathic thrombocytopenic purpura because it resolved with high-dose steroids and intravenous immunoglobulin. She was discharged home 11 days after admission. The patient remained afebrile for 1 week at home. During this period she developed new-onset progressive upper abdominal pain with meals lasting 20–30 minutes. She denied associated constitutional symptoms, diarrhea, hematochezia, or melena.

14 – Mesenchymal Tumors of the Central Nervous System

Mesenchymal tumors involving the central nervous system (CNS) comprise a number of benign, malignant, and non-neoplastic entities. Mesenchymal tumors include entities originating from mesodermal-derived precursor cells that develop into bone, cartilage, or other connective tissues, such as blood vessels, adipose tissue, smooth muscle, or fibroblasts; in the CNS they most commonly arise from the meninges rather than the CNS parenchyma. Histologic features and terminology of these tumors are often identical to the extracranial soft tissue and bone counterparts, yet occasional entities may show unique clinicopathologic or molecular characteristics in the CNS, and the list of tumor types seen in the CNS is typically not as diverse as that in extracranial tissues. This chapter focuses on the tumor types that may be encountered by a surgical pathologist, neurosurgeon, or neuro-oncologist at a relatively higher frequency. The chapter is arranged in general categories of mesenchymal tumors according to cellular differentiation/tissue type, including adipocytic, bone, cartilaginous, notochordal, fibroblastic/myofibroblastic, smooth muscle, skeletal muscle, vascular, primitive tumors, undifferentiated tumors, and miscellaneous. Each subcategory includes a discussion of benign through malignant spectrum of lesions, with sections on definitions, clinical manifestations, radiologic features and gross pathology, histopathology, variants and/or grading, differential diagnosis, ancillary studies, genetics, and finally treatments/prognosis. In the revised edition, we have placed a greater emphasis on molecular diagnostics in CNS mesenchymal tumors.

Genetic and molecular reappraisal of spindle cell adamantinoma of bone reveals a small subset of misclassified intraosseous synovial sarcoma

Adamantinoma represents a distinct group of bone tumors showing both mesenchymal and epithelial differentiation most commonly involving the tibial diaphysis. Most adamantinomas contain a fibro-osseous component and an epithelial component consisting of squamous or basaloid cells. Adamantinomas are considered malignant neoplasms requiring en bloc excision that frequently recur locally and can rarely metastasize. Rare adamantinomas show an epithelial component consisting predominantly of monomorphic spindle cells, which, combined with an epithelial immunophenotype, can mimic monophasic synovial sarcoma. Synovial sarcoma is very rare in bone. It is considered a high-grade sarcoma that typically necessitates chemotherapy. However, the relationship between spindle cell adamantinoma and intraosseous synovial sarcoma has not been investigated. The current study was prompted by identification of a presumed spindle cell adamantinoma of the tibia with diffuse keratin expression that harbored a SS18 gene region rearrangement. FISH of eight additional bone tumors initially classified as spindle cell adamantinoma based on clinicoradiopathologic findings revealed one additional case with SS18 rearrangement. Histologically, both intraosseous synovial sarcoma and spindle cell adamantinoma demonstrated uniform fusiform nuclei with scant cytoplasm, short fascicles and low mitotic activity. The adamantinomas, but not the synovial sarcomas, were more likely to show overt epithelial differentiation in the form of pseudoglands or squamous nests. Immunohistochemistry of all cases, irrespective of SS18 status, showed diffuse keratin positivity in the spindle cell component, and less consistent EMA positivity. Clinical follow-up was available in both intraosseous synovial sarcomas, one of which recurred and the other metastasized. Two of the six spindle cell adamantinomas with follow-up metastasized. The above findings highlight the morphologic and immunophenotypic overlap between spindle cell adamantinoma and intraosseous synovial sarcoma of the tibia. Investigation of SS18 status to exclude synovial sarcoma is suggested prior to rendering a diagnosis of spindle cell adamantinoma.

Rare case of a recurrent juvenile ossifying fibroma of the lumbosacral spine

Juvenile ossifying fibroma (JOF) is a rare benign bone tumor that occurs most frequently in the craniofacial bones of children and young adults. There are few case reports that describe its involvement outside the craniofacial skeleton, especially within the spinal column. While JOF is classified as a benign lesion, it may be locally aggressive and demonstrate a high propensity for recurrence, even after resection. Definitive surgical management may be challenging in naive cases, but it is particularly challenging in recurrent cases and when extensive spinal reconstruction is warranted. In this report, the authors describe the diagnosis and surgical management of a 29-year-old man who presented with a large recurrent sacral trabecular-subtype JOF. A review of literature regarding JOFs, management of recurrent primary spinal tumors, and sacral reconstruction are discussed.