By the current WHO classification, benign notochordal cell tumor (BNCT) and chordoma comprise the entire spectrum of notochordal-derived tumors. They have defined radiologic and histologic criteria, and differ considerably in management and clinical outcome. Chordomas are malignant tumors; they show progressive, destructive growth and have the capacity for metastasis. In contrast, BNCT are benign and show limited intraosseous growth. Patients with BNCT can be managed with serial imaging or conservative excision, whereas patients with spinal/sacral chordomas typically undergo radical en bloc resection often with adjuvant therapy and significant morbidity. As such, the distinction between BNCT and chordoma is critically important. We have seen 4 unusual notochordal tumors with radiologic and/or histologic features that defy classification as either BNCT or chordoma. Cases occurred in 4 adults (53 to 83 y), and involved the lumbar spine (N=2) and sacrum (N=2). Three cases had subtle radiologic features of cortical permeation with minimal soft tissue extension. All 4 cases had the characteristic histologic features of BNCT; however, 2 cases also had focal myxoid change. Three patients were followed with serial imaging (follow-up range, 26 to 120 mo); 2 showed no disease progression and 1 had a 10-year cumulative interval growth of 3.7 mm. One patient underwent sacrectomy. The tumor was examined in toto and had the characteristic histologic features of BNCT, with the exception of minimal soft tissue extension. On the basis of these observations, we propose a provisional designation of atypical notochordal cell tumors (ANCT) be used for the subset of notochordal-derived tumors that fail to fulfill current diagnostic criteria for either BNCT or chordoma. We would argue that designating these atypical notochordal tumors as chordoma precipitates potentially overly aggressive surgical management. Patients with ANCT may be better managed by close observation and serial imaging. Additional studies with more cases and longer clinical follow-up should clarify the relationship of ANCT to BNCT and chordoma.
Histologic Spectrum of Giant Cell Tumor (GCT) of Bone in Patients 18 Years of Age and Below
Although the majority of giant cell tumors (GCTs) of the bone occur in adult patients, occasionally they arise in the pediatric population. In this setting they may be mistaken for tumors more commonly seen in this age group, including osteosarcoma, aneurysmal bone cyst, and chondroblastoma. All cases of primary GCT of the bone arising in patients 18 years and below were retrieved from our institutional archives and examined with emphasis on the evaluation of various morphologic patterns. Clinical/radiologic records were reviewed when available. Analysis for H3F3A/H3F3B mutations was performed in a subset of cases. Sixty-three (of 710) patients treated at our institution for GCT were 18 years of age and below. The following morphologic patterns were identified: fibrosis (31 cases, 49%), reactive-appearing bone (26, 41%), cystic change (7, 11%), foamy histiocytes (6, 10%), secondary aneurysmal bone cyst (3, 5%), and cartilage (2, 3%). Infarct-like necrosis was present in 17 tumors (27%), and the mitotic rate ranged from 0 to 35 mitoses/10 high-power fields (median 5 mitoses/10 high-power field). Follow-up information (n=55; 6 mo to 69.6 y; median, 11.6 y) showed 21 patients with local recurrence (38%) and 2 patients with lung metastasis (4%). Polymerase chain reaction with sequencing showed that 5 of 5 tested cases harbored H3F3A mutations. In summary, GCT arising in the pediatric population is rare, representing 9% of GCTs seen at our institution. The morphologic spectrum of these tumors is broad and similar to that seen in patients above 18 years of age. It is important to recognize that matrix formation may be observed in GCT, including reactive-appearing bone and cartilage, as well as areas of fibrosis mimicking osteoid production, to avoid misclassification as osteosarcoma or other giant cell–rich lesions common in children.
Extent of atypical hyperplasia stratifies breast cancer risk in 2 independent cohorts of women
Neuromuscular choristoma (NMC) is a very rare, developmental malformation characterized by the endoneurial intercalation of mature muscle fibers among peripheral nerve fibers. NMC typically arises in the major proximal peripheral nerves, most commonly the sciatic nerve, and may involve the lumbosacral and brachial plexus. Patients present clinically with progressive neuropathy or plexopathy. NMC is strongly associated with development of a fibromatosis, histologically identical to conventional desmoid-type fibromatosis (NMC-fibromatosis). The development of NMC-fibromatosis is often precipitated by iatrogenic trauma (ie, biopsy). Desmoid-type fibromatosis is characterized by CTNNB1 exon 3 mutations, which result in aberrant nuclear β-catenin localization and dysregulated canonical Wnt signaling. In contrast, the pathogenesis of NMC and NMC-fibromatosis is unknown. Desmoid-type fibromatosis expresses estrogen receptors (ER), specifically the ER-beta isoform (ERβ), and endocrine therapies may be used in surgically unresectable cases. In contrast, the ER expression profile of NMC-fibromatosis is unknown. We evaluated a series of NMC and NMC-fibromatosis for CTNNB1 mutations, β-catenin expression, and ER isoform expression. Five NMCs occurred in 2 female and 3 male patients (median age: 14 y, range <1 to 42 y), as masses involving the sciatic nerve (N=4) or brachial plexus (N=1). Four (of 5) NMCs had CTNNB1 mutations: 3 c.134 C>T (p.S45F) and 1 c.121 A>G (p.T41A). Four patients subsequently developed NMC-fibromatosis, and all 4 cases contained CTNNB1 mutations, including 1 p.T41A and 3 p.S45F mutations. In 3 patients, the NMC and NMC-fibromatosis had identical CTNNB1 mutations. Only 1 NMC had no detectable CTNNB1 mutation; however, the patient’s subsequent NMC-fibromatosis had a CTNNB1 p.T41A mutation. All NMC and NMC-fibromatosis showed aberrant nuclear localization of β-catenin, nuclear ERβ expression, and no ERα expression. The presence of CTNNB1 mutations both in NMC and NMC-fibromatosis may be a shared molecular genetic abnormality underlying their pathogenesis.
Atypical cartilaginous tumor/chondrosarcoma, grade 1, of the mastoid in three family members: A new entity