Current status of immunotherapy for gastrointestinal stromal tumor.

Gastrointestinal stromal tumors (GIST) contain tumor-infiltrating immune cells and their presence provides an opportunity and rationale for developing effective forms of immunotherapy. The types of tumor-infiltrating inflammatory cells and relevant immune checkpoint inhibitors are the focus of active investigation. The most numerous tumor-infiltrating inflammatory cells are tumor-associated macrophages (TAMs) and CD3+ T cells. Studies have shown that patients with GISTs that harbor increased numbers of CD3+ T cells have better outcomes. However, the clinical behavior of GIST has not been shown to correlate with the number of TAMs. The biological significance of other less frequent tumor-infiltrating immune cells including tumor-infiltrating neurtrophils (TINs), natural killer cells (NKs), B cells, dendritic cells (DCs) remains unclear. The immune checkpoint inhibitors CTLA-4, PD1/PDL1 and TIM3/galectin-9 are molecules that can be targeted by synthesized antibodies. Clinical and pre-clinical trials using this approach against immune checkpoint inhibitors, anti-KIT antibody and the generation of chimeric antigen receptor (CAR) T-cells have shown promising results. The treatment of GIST with immunotherapy is complex and evolving; this article reviews its current status for patients with GISTs.

Timing of chemotherapy and surgery in a murine osteosarcoma model.

The sequential use of chemotherapy and surgery in the treatment of osteosarcoma developed in an empirical fashion without the benefit of investigations in animal models. The MGH-OGS murine osteosarcoma is a transplantable tumor that resembles the human disease with respect to histology, local invasiveness, metastatic characteristics, tumor ploidy, and its response to chemotherapy. We have used this tumor model to investigate the efficacy of preoperative, perioperative, and postoperative chemotherapy on the development of pulmonary metastases in three different experimental protocols. In each experimental design, perioperative chemotherapy demonstrated a significant advantage in preventing systemic relapse.

Radiation in management of patients with dermatofibrosarcoma protuberans.

PURPOSE: The preferred treatment of dermatofibrosarcoma protuberans (DFSP) is wide resection, namely, margins > or = 3 cm beyond the evident disease and histologically negative margins. We assess the success achieved by radiation combined with surgery for positive/close margins or by radiation alone for those tumors that are not resectable for technical/medical reasons. The literature on this point is virtually nonexistent. MATERIALS AND METHODS: The outcome of treatment of 18 patients with DFSP by radiation alone (n = 3) and radiation and surgery (n = 15) at the Massachusetts General Hospital was assessed. All of the lesions at the time of the treatment by radiation alone or combined with surgery were less than 10 cm. This was the maximum dimension. The actual tumor volume was much less than indicated by this maximum dimension, as the tumors were usually relatively flat. RESULTS: The 10-year actuarial local control rate was determined to be 88%. Local control was realized in the three patients treated by radiation alone, with follow-up periods of > or = 9 years. Among 15 patients treated by radiation and surgery, there have been three local failures; the 10-year actuarial local control rate was 84%. The three local failures occurred in 12 patients whose surgical margins were positive. One of these three local failures developed in the group of two patients whose lesions were scored as grade II. CONCLUSION: Radiation in well-tolerated dose schedules is an effective option in the management of patients with DFSP. This appears to be true for radiation alone or postoperatively for margin-positive disease (primary or recurrent).

Mechanical properties of trabecular bone within and adjacent to osseous metastases.

Despite radiographic and histologic evidence of trabecular bone density changes within and adjacent to osseous metastases, there currently exist no data to demonstrate whether these changes are important in predicting the risk of fracture. To determine if these density changes result in significant reductions in mechanical properties, trabecular bone specimens were prepared from lower thoracic and lumbar vertebrae from two cadavers with radiographic, gross, and histologic evidence of lytic and/or blastic osseous metastases. Each specimen was classified as normal, lytic, or blastic based on appearance in fine-grain radiographs of 8-9 mm thick coronal plane sections. Specimens were tested to failure in uniaxial compression, and tissue and apparent densities were measured. Mean tissue densities were within normal ranges. The mean apparent density for all specimens combined was within the normal range for human vertebrae, and the mean apparent density for radiographically normal (0.131 g/ml) and lytic (0.111 g/ml) specimens was less than the mean apparent density of blastic (0.182 g/ml) specimens (p < 0.02). The moduli of lytic and blastic specimens were less than for normal specimens (p < 0.025). The strength of lytic specimens was less than normal (p = 0.057), but the strength of blastic specimens was not (p > 0.1). Apparent density explained significant fractions of the variations in both modulus (p < 0.001) and strength (p < 0.001). The data suggest that blastic changes associated with osseous metastases to trabecular bone disrupt the normal dependence of trabecular mechanical properties on apparent density, but lytic changes do not.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of 92 kD type IV collagenase/gelatinase B in human osteoclasts.

The digestion of type I collagen is an essential step in bone resorption. It is well established that osteoclasts solubilize the mineral phase of bone during the resorptive process, but the mechanism by which they degrade type I collagen, the major proteinaceous component of bone, is controversial. Differential screening of a human osteoclastoma cDNA library was performed to characterize genes specifically expressed in osteoclasts. A large number of cDNA clones obtained by this procedure were found to represent 92 kD type IV collagenase (gelatinase B; MMP-9, EC 3.4.24.35), as well as tartrate-resistant acid phosphatase. In situ hybridization localized mRNA for gelatinase B to multinucleated giant cells in human osteoclastomas. Gelatinase B immunoreactivity was demonstrated in giant cells from eight of eight osteoclastomas, osteoclasts in normal bone, and osteoclasts of Paget's disease by use of a polyclonal antiserum raised against a synthetic gelatinase B peptide. In contrast, no immunoreactivity for 72 kD type IV collagenase (gelatinase A; MMP-2, EC 3.4.24.24), which is the product of a separate gene, was detected in osteoclastomas or normal osteoclasts. We propose that the 92 kD type IV collagenase/gelatinase B plays an important role in the resorption of collagen during bone remodeling.

Paracoccidioidomycosis of bones and joints. A clinical, radiologic, and pathologic study of 9 cases.

Paracoccidioidomycosis is a systemic fungal infection endemic to Central and South America. It is associated with a broad spectrum of clinical manifestations and has been classified into acute and chronic forms. The latter is the most common type and usually affects male agricultural workers in rural communities. The disease typically begins in the lungs producing varying degrees of parenchymal damage, and in a significant number of cases the organism spreads through bronchogenic, lymphatic, or hematogenous routes to involve 1 or more organs. Bone and joint infection is relatively uncommon and has not been well described in the English literature. Much of the information on this form of the disease has been derived from radiographic and autopsy studies on patients with severe or fatal infections in whom skeletal involvement was a minor or incidental finding. We describe our experience with 9 cases in which osteoarticular manifestations were the sole or 1 of the few major complications of the disease. All 9 patients were male, from 9 to 49 years of age (mean, 36.6 yr). Six were farmers. Evidence of visceral infection was present in 6 patients, in all of whom the lungs were considered the primary site of disease. The osteoarticular lesions were symptomatic in all cases, with the duration of symptoms ranging from 1 week to 2 years. The lesions were centered in bone in 2 cases: they manifested radiographically as circumscribed areas of lysis with or without a rim of sclerosis. The disease was centered in joints in 7 cases; the associated radiographic changes included evidence of joint effusion, periarticular bony erosions, and narrowing of the joint space. Biopsy of the involved skeletal site revealed compact or loose granulomas containing variable numbers of fungi. Although follow-up information was not available for all patients, those treated with TMP-SMX (and 1 patient who also received amphotericin B) and who were followed had prompt resolution of their signs and symptoms. Our findings substantiate some of what is known about the epidemiology of bone and joint involvement in chronic paracoccidioidomycosis. Our patients exhibited features of skeletal infection that have not been emphasized previously, however, including 1) frequent involvement of large joints or long bones of the extremities, 2) presentation with relatively rapidly developing musculoskeletal symptoms, and 3) manifestation as a solitary joint or bone lesion with or without concurrent clinically detectable pulmonary disease. Bone and joint paracoccidioidomycosis should be considered in the differential diagnosis in patients who have skeletal lesions with or without pulmonary involvement and have either lived in or traveled through endemic areas. Early diagnosis and treatment with antifungal medications can achieve an excellent outcome with limited local sequelae.

Matrix metalloproteinase digestion of aggrecan in human cartilage tumours.

Substantial experimental and clinical evidence suggests that the catabolism of extracellular matrix components is a prerequisite for invasive and metastatic behaviour of solid tumours. Chondrosarcomas are malignant cartilaginous tumours that most commonly arise in bone, and the large aggregating proteoglycan aggrecan is a major component of the extracellular matrix of these tumours. Matrix metalloproteinases (MMPs) have been implicated in tumour invasiveness. The purpose of this study was to determine whether MMPs play a role in aggrecan catabolism in cartilage tumours. In order to detect aggrecan digestion products resulting from in vivo cleavage at the MMP site, protein extracts from human articular cartilage and from various cartilage tumours were analysed by Western blot using an antibody to the FVDIPEN neoepitope generated by MMP cleavage. Examination of cartilage extracts revealed a trend of increasing aggrecan digestion at the MMP site with age. One hyaline chondrosarcoma and three osteochondromas lacked detectable aggrecan fragments with the carboxy terminal FVDIPEN neoepitope. Two osteochondromas gave weak signals. However, all chondrosarcomas with degenerating extracellular matrix or with a myxoid component exhibited strong FVDIPEN immunoreactivity. These results demonstrate that, in contrast to the benign cartilage tumour osteochondroma, human chondrosarcomas contain abundant aggrecan degradation products resulting from cleavage in vivo at the MMP site in the interglobular domain. These data support the concept that MMPs participate in the degradation of extracellular matrix in chondrosarcoma, allowing the neoplastic chondrocytes to escape local confinement, migrate, and invade neighbouring and remote tissues.

Dermatofibrosarcoma protuberans treated with radiation therapy.

Dermatofibrosarcoma Protuberans is an uncommon soft tissue tumor that is locally aggressive, prone to recur locally following excision, and has a low propensity for metastasis. Ten patients have received radiation (both external beam and interstitial implant) as part of, or as their only treatment, at Massachusetts General Hospital from 1979-1987. Three patients received radiation alone (66.7-75 Gy) for gross palpable disease. One patient has slowly regressing nodules at 33 months; the other two had complete regression and are free of disease at 24 and 26 months posttreatment. Seven patients received radiation in conjunction with surgery. One received both preoperative and postoperative radiation and six received postoperative radiation (60-67 Gy) for microscopic residual disease following resection. Six of these seven patients are free of disease 16 to 105 months following treatment. One patient, with diffuse microscopic tumor infiltration of the scalp, had a local recurrence within the radiation field 16 months following 64.4 Gy. There has been no significant treatment related morbidity. Even though the present experience is limited and the follow-up brief, it does suggest that radiation can be considered a viable therapeutic option in the patient who has a lesion that is not resectable.

Adult soft tissue sarcomas of the head and neck treated by radiation and surgery or radiation alone: patterns of failure and prognostic factors.

PURPOSE: To analyze our experience treating soft tissue sarcomas of the head and neck in adults, and to identify patterns of failure and prognostic factors. METHODS AND MATERIALS: The records of 57 patients with Stage M0 disease treated by radiation with or without surgery between 1972 and 1993 were reviewed. Median follow-up time was 4.3 years (range, 1.1-16.8 years). A group of potential prognostic factors was evaluated, including age at diagnosis, sex, initial tumor presentation (primary vs. recurrent), grade, T-stage, direct tumor extension, tumor depth, duration of treatment, and radiation dose. RESULTS: The subset of angiosarcomas (11 out of 57 patients) had a considerably adverse effect on treatment outcome for the total group of sarcomas, with actuarial 5-year overall survival (OS), locoregional control (LRC), and freedom from distant metastasis (FDM) rates being 31%, 24%, and 42%, respectively. In contrast, for the remaining 46 patients with other histopathological tumor types, OS, LRC, and FDM rates were significantly higher (74%, 69%, and 83%, respectively). For this group of patients, significant prognostic factors identified by uni- and multivariate analysis included tumor grade as a predictor of OS and T-stage as a predictor of LRC (p < or = 0.050). Those patients who experienced a locoregional recurrence were at a significantly increased risk of dying (p = 0.004 in a multivariate model). All 17 patients without direct tumor extension to neurovascular structures, bone, contiguous organs, or skin remained free from distant failure. In contrast, 27% of 29 patients with direct extension had developed distant metastases at 5 years. In multivariate analysis, the absence of direct extension was a positive predictor of FDM (p = 0.007) and of OS (p = 0.034). CONCLUSIONS: 1) Angiosarcomas of the head and neck have a considerably poorer prognosis than other soft tissue sarcomas of this site. 2) In addition to tumor grade and size, direct tumor extension may be a useful additional staging parameter. 3) High rates of locoregional failure in the head and neck area, a potential cause of morbidity and death, indicate a need for improved treatment strategies.

Fibromatoses: from postsurgical surveillance to combined surgery and radiation therapy.

The results of management of two groups of patients with musculoaponeurotic (desmoid tumors) and plantar fibromatoses seen at Massachusetts General Hospital (MGH) during the period 1970-1985 are examined: (a) 26 patients who had had surgical resection for their primary fibromatosis but whose surgical margins were positive and who received no further treatment; and (b) 24 patients who were treated for their primary or recurrent fibromatosis by radiation alone or combined with surgery. For the 26 patients who were only observed, despite the positive surgical margins, 9 have recurred; the actuarial continuous local control rate at 5 years was 68% (a median follow-up of 70 months). Five patients had gross disease left after surgery and all of them failed. Seventeen of 21 patients who had grossly complete resection have local control; the four failures have been salvaged. This result supports the rationale for a no treatment but a thorough and close follow-up policy for patients with positive margins after grossly complete resection of a primary desmoid or fascial fibromatosis. There is no risk of metastasis in these patients and hence the effort toward a conservative policy which defers radiation merits interest and further study. Of the second group, 23 patients were treated for gross disease and one patient for microscopic disease after surgical resection. All of the 10 patients who were treated for primary desmoid tumor have local control. Among the 14 recurrent desmoid tumors there have been five local failures, after treatment by radiation alone or radiation + surgery. Three patients treated by radiation alone are currently scored as incompletely regressed tumors. Accordingly 16 of the 24 patients are scored as local controls without evidence of disease and 19 of the 24 are scored as local control (complete response or partial but stable response).

Individualizing management of aggressive fibromatoses.

PURPOSE: To examine prognostic indicators in aggressive fibromatoses that may be used to optimize case-specific management strategy. METHODS AND MATERIALS: One hundred and seven fibromatoses presenting between 1971 and 1992 were analyzed. The following treatment modalities were utilized: (a) surgery alone for 51 tumors; (b) radiation alone for 15 tumors; and (c) radiation and surgery (combined modality) for 41 tumors. Outcome analysis was based on 5-year actuarial local control rates. RESULTS: Control rates among surgery, radiation therapy, and combined modality groups were 69%, 93%, and 72%. Multivariate analysis identified age < 18 years, recurrent disease, positive surgical margins, and treatment with surgery alone as predictors for failure. Patients treated with surgery alone had control rates of 50% (3 of 6) for gross residual, 56% for microscopically positive margins, and 77% for negative margins. Radiation and surgery resulted in rates of 59% for gross residual, 78% for microscopically positive margins, and 100% (6 of 6) for negative margins. For recurrent vs. primary tumors, control was achieved in 48% vs. 77%, 90% vs. 100% (5 of 5), and 67% vs. 79% in the Surgery, Radiation, and Combined modality Groups, respectively. Patients presenting with multiple disease sites tended to have aggressive disease. A radiation dose-control relation to > 60 Gy was seen in patients with unresected or gross residual disease. Of the patients, 23 with disease involving the plantar region had a control rate of 62%, with significantly worse outcomes in children. CONCLUSIONS: These results are consistent with those found in the relevant literature. They support primary resection with negative margins when feasible. Radiation is a highly effective alternative in situations where surgery would result in major functional or cosmetic defects. When negative surgical margins are not achieved in recurrent tumors, radiation is recommended. Perioperative radiation should be considered in other high-risk groups (recurrent disease, positive margins, and plantar tumors in young patients). Doses of 60-65 Gy for gross disease and 50-60 Gy for microscopic residual are recommended. Observation may be considered for primary tumors with disease remaining in situ when they are located such that progression would not cause significant morbidity. Although plantar lesions in children may represent a group at high risk for recurrence or aggressive behavior, the greater potential for radiation-induced morbidity in this group must also temper its use. Given the inconsistent nature and treatment response of this tumor, it is fundamental that treatment recommendations should be made based on the risk:benefit analysis for the individual patient, dependent on tumor characteristics and location, as well as patient characteristics and preferences.

Multiple cutaneous neuromuscular choristomas. Report of a case and a review of the literature.

We report a case of two neuromuscular choristomas occurring in separate cutaneous locations in a healthy 3-month-old infant. Both lesions had an identical histologic appearance and were composed of mature skeletal muscle cells admixed with nerve fibers. In all previous reports, neuromuscular choristoma has arisen in association with a major nerve, and most lesions have been solitary. The two separate cutaneous choristomas in this case suggest that this lesion may arise from the neuroectodermal-derived Schwann cell.

Retroperitoneal xanthogranuloma in a patient with Erdheim-Chester disease.

A case of Erdheim-Chester disease with retroperitoneal and renal sinus xanthogranuloma that occurred in a 50-year-old woman is presented. The 12 previously reported cases of Erdheim-Chester disease associated with retroperitoneal xanthogranuloma are reviewed and compared with 13 sporadic cases of retroperitoneal xanthogranuloma. Retroperitoneal xanthogranuloma is distinguished from inflammatory malignant fibrous histiocytoma by its lack of neutrophils, inconspicuous vascularity, lack of nuclear atypia, and abundant collagen. It is distinguished from inflammatory fibrosarcoma by its numerous foamy histiocytes, relative lack of plasma cells, and lack of nuclear atypia; it is distinguished from retroperitoneal fibrosis principally by its many foamy histiocytes, lack of plasma cells, and lack of vasculitis.

Multiple enchondromas associated with spindle-cell hemangioendotheliomas. An overlooked variant of Maffucci's syndrome.

Maffucci's syndrome is classically defined as the association of multiple enchondromas and hemangiomas. Spindle-cell hemangioendothelioma (SCH), a recently described vascular tumor of purported low malignant potential, has both cavernous hemangioma and Kaposi-like features. We report six patients with Maffucci's syndrome in whom all vascular lesions were SCH. The enchondromas involved the small and long tubular bones of the extremities in all of these patients; flat bones were also involved in three patients. The SCH usually arose in the extremities, distal to the knees and elbows. Five of the six patients had multiple and separate nodules of SCH, and in four patients there was recurrent or persistent SCH within 6 months to 4 years after initial removal. One patient also had a vascular tumor in the spleen mainly with features of a low-grade angiosarcoma with separate SCH-like foci. None of the SCH have metastasized within a follow-up period averaging 20 years. Five patients are alive 14 to 31 years after presentation. One patient died from metastatic dedifferentiated chondrosarcoma. The patient with the low-grade splenic angiosarcoma is alive approximately 2 years after diagnosis. Reappraisal of the older literature suggests that some of the vascular tumors occurring in Maffucci's syndrome, previously diagnosed as hemangiomas, may in fact be SCH. The apparent association between Maffucci's syndrome and SCH, the presence of SCH in other congenital syndromes, and the young patient age and multicentric distribution of SCH unassociated with Maffucci's syndrome raise the possibility that SCH may be a manifestation of a congenital mesodermal disorder with a genetic background related to Maffucci's syndrome. Although the behavior of SCH appears to be one of a locally recurrent or persistent multicentric lesion that does not metastasize, the association of SCH-like foci in a low-grade angiosarcoma of the spleen raises the possibility that SCH may rarely be associated with a higher grade lesion. Therefore, SCH, at least in the setting of Maffucci's syndrome, should be carefully monitored.

Subchondral acute inflammation in severe arthritis: a sterile osteomyelitis?

Although arthritis is often associated with synovial inflammation, the osseous changes in inflammatory and degenerative arthritis are principally reactive, and typically lack an acute inflammatory component. We have recently encountered several osteoarticular specimens removed at the time of large joint arthroplasty that have shown a distinctive pattern of subchondral acute inflammation (SCAI) resembling acute bacterial osteomyelitis. These microscopic findings heretofore have not been recognized as a component of the histopathology of arthritis. To determine the frequency of SCAI, we examined slides (mean four per case) from 164 hip arthroplasties performed at one of our institutions in a single year. A total of 10 cases of SCAI, including the 4 original examples (2 humeral head specimens, 2 femoral head specimens) and 6 identified from the slide review are described in this report. Eight patients were female and two were male (ages 54-86 years, mean 70, median 70). All had severe degenerative joint disease, six had rheumatoid arthritis, and three had osteonecrosis. In none was there a clinical or intraoperative suspicion of infection. Cultures of joint fluid or bone were not performed. In all cases, the inflammation was subchondral (within 1.0 cm of the joint surface), and it was frequently associated with subchondral cysts. In osteonecrotic foci, the suppurative inflammation was diffuse within the marrow space, whereas in viable bone it was nodular and vaguely granulomatous. Special stains for organisms were negative. None of the patients was treated with long-term IV antibiotics. There has been no septic loosening of the prostheses at follow-up intervals ranging from 5 to 36 months (mean: 17 months). Our observations, to the best of our knowledge, are novel. Although we cannot definitively exclude bacterial infection as a cause of SCAI, the histologic and clinical features suggest that SCAI likely represents a noninfectious sterile form of inflammation. Subchondral acute inflammation is possibly secondary to synovial fluid insudation into subchondral cancellous bone in the setting of severe osteoarthritis and/or rheumatoid arthritis.

Intramuscular myxoma: a clinicopathologic study of 51 cases with emphasis on hypercellular and hypervascular variants.

Intramuscular myxoma (IM) is a benign soft-tissue tumor that presents as a deeply seated mass confined to skeletal muscle. Surgical excision is virtually always curative. Recurrence, even after incomplete resection, is exceptional. Intramuscular myxoma is classically described as hypocellular and hypovascular, and is composed of cytologically bland stellate and bipolar fibroblasts separated by abundant extracellular myxoid matrix. What is underemphasized, however, is that IMs often show areas of increased cellularity and vascularity that can lead to a mistaken diagnosis of sarcoma, especially myxofibrosarcoma, low-grade fibromyxoid sarcoma, and myxoid liposarcoma. In this report, we describe the clinicopathologic features of 51 IMs with special emphasis on those that exhibit these "hypercellular regions." The patients included 35 women and 16 men who ranged in age from 27 to 89 (mean 52) years. The tumors measured from 2 to 15 (average 5.6) cm and all had a gelatinous, lobulated cut surface. Histologically, they all demonstrated classic hypocellular, hypovascular regions. Thirty-eight tumors contained areas of relative increased cellularity that occupied from 10 to 80% of the tumor. These foci had increased numbers of cells, more prominent vascularity, and often increased collagen content. The hypercellular regions were not associated with cytologic atypia of the constituent cells, mitotic activity, or necrosis. Follow-up information was available for 32 patients and ranged from 3 to 108 (average 30) months. No tumor recurred or metastasized. Areas of hypercellularity are common in IMs. Their recognition is important to avoid an erroneous diagnosis of sarcoma.

Gastrointestinal stromal tumor versus intra-abdominal fibromatosis of the bowel wall: a clinically important differential diagnosis.

Intra-abdominal fibromatosis (IAF) is an uncommon benign neoplasm that usually occurs in the mesentery or retroperitoneum and may, on occasion, mimic a gastrointestinal stromal tumor (GIST). Differentiating between these two entities is important clinically because IAF is a benign tumor whereas GISTs frequently have malignant potential. In this study, the authors identified 13 cases of IAF with prominent involvement of the bowel wall as well as 35 GISTs of the small intestine, colon, or mesentery and analyzed their clinical, gross, histologic, immunophenotypic, and ultrastructural characteristics to identify important distinguishing features. Patients with IAF were younger (mean, 34 yrs) than patients with GIST (mean, 54 yrs). Both types of tumors tended to be large, but GISTs were soft and lobulated with hemorrhage, necrosis, or cystification whereas IAFs were firm, tan, and homogeneous. Histologic features characteristic of GIST included the presence of spindle or epithelioid cells with variable architecture, mitotic activity (range, <1-95 mitoses/50 high-power fields [hpf]; mean, 15 mitoses/50 hpf), nuclear atypia, and myxoid or hyalinized stroma. Necrosis and hemorrhage were seen in 16 and 25 tumors, respectively. In contrast, IAFs were composed of broad, sweeping fascicles of monotonous spindle cells with mitotic activity (range, <3-11 mitoses/50 hpf; mean, 4 mitoses/50 hpf), bland nuclear features, and finely collagenous stroma. Necrosis, hemorrhage, and myxoid degeneration were not seen. Immunohistochemical studies performed on a limited number of GISTs and IAFs demonstrated that cells expressed vimentin (100% GIST and IAF), CD117 (88% GIST and 75% IAF), CD34 (42% GIST and 0% IAF), smooth muscle actin (63% GIST and 75% IAF), muscle actin (75% GIST and 75% IAF), desmin (8% GIST and 50% IAF), and S-100 protein (16% GIST and 0% IAF). Ultrastructural analysis of 21 GISTs revealed incomplete smooth muscle differentiation in some tumors whereas IAFs were shown to have complete myofibroblastic/fibroblastic differentiation. Information regarding clinical outcome was available on 29 patients and revealed that three patients with histologically benign GISTs were alive with no evidence of disease at 5 months to 6 years (mean, 3.5 yrs) and one patient with a histologically benign tumor died of disease after 7 years. Of patients with histologically malignant GIST, one died of surgical complications, 10 were alive without disease at I to 13 years (mean, 5.4 yrs), four were alive with disease at 4 months to 15 years (mean, 3.8 yrs), three had disseminated disease at operation, and seven were dead of disease at 10 months to 3 years (mean, 2.2 yrs). Follow up of eight patients with IAF demonstrated that five were alive without disease at 4 months to 15 years (mean, 5.3 yrs) and three had recurrences at 1 (two patients) and 2 years (one patient). In summary, IAFs can have many features (large size, infiltration of adjacent structures, mitotic activity) that can cause diagnostic confusion with GISTs and, importantly, the degree of mitotic activity present in IAFs may overlap that seen in malignant GISTs. These entities can be distinguished primarily by their light microscopic and ultrastructural features but there is a notable overlap in their immunohistochemical profiles. The distinction between these neoplasms is important because there are important clinical implications for the patient.

Primary lymphoma of peripheral nerve: report of four cases.

Lymphoma presenting as a solitary tumor of peripheral nerve is exceedingly rare, with only six previously reported cases. The authors describe an additional four cases of primary lymphoma of peripheral nerve involving the sciatic nerve (two cases), the radial nerve, and the sympathetic chain and spinal nerve. The patients were two men and two women with an average age of 55.5 years. All tumors were high-grade B-cell lymphomas. Two patients experienced relapse of disease with involvement of other nervous system sites and died of lymphoma. One patient is alive with stable local disease at 57 months. The fourth patient is alive with no evidence of disease at 54 months. Expression of neural cell adhesion molecule (CD56) has been reported to correlate with an increased incidence of central nervous system involvement in peripheral T-cell lymphoma; all their cases were CD56 negative. Recent reports indicate a high proportion of primary brain lymphomas show loss of CDKN2A/p16 gene expression. Therefore, CDKN2A/p16 was evaluated in their patients both by polymerase chain reaction and by immunohistochemistry for the p16 protein. The authors found homozygous deletion of the CDKN2A/p16 gene in one of three patients studied, confirmed immunohistochemically by absent staining for p16. The fourth patient showed absent staining for p16, suggesting inactivation of the gene in this case as well. The two patients with p16 loss both died of lymphoma, whereas the two patients with normal p16 expression are alive. Primary lymphoma of peripheral nerve is a rare neoplasm, usually of large B-cell type, has a variable prognosis, and appears to have less consistent loss of p16 expression than primary central nervous system lymphoma.

Chordoma periphericum: a case report.

The authors describe a tumor that had the histologic and ultrastructural features and immunohistochemical profile of an axial chordoma, but arose in the distal ulna. A skeletal survey failed to show any other site of involvement. The tumor was resected, and the patient remains free of disease 2 1/2 years later. Rare tumors with the histologic features of chordoma have been reported in appendicular locations. Chordoma periphericum, a tumor that has the potential to metastasize, needs to be distinguished from parachordoma because no classic parachordoma has been reported to disseminate.

Lipomatous hemangiopericytoma. A histologic, ultrastructural and immunohistochemical study of a unique variant of hemangiopericytoma.

We report three cases of a unique, previously undescribed soft tissue tumor composed of mature adipocytes and hemangiopericytomatous areas, for which we propose the term lipomatous hemangiopericytoma. The tumors occurred in adults and were located in the sinonasal area, the soft tissue of the shoulder, and the retroperitoneum. The tumors ranged in size from 4 to 10 cm in greatest diameter and grossly were solid and ranged from tan to yellow. Histologically, they were composed of a variable admixture of benign lipomatous and hemangiopericytomatous components. Immunohistochemically, they stained with antibodies to vimentin and not to alpha-smooth-muscle actin, muscle-specific actin, desmin, S-100 protein, glial fibrillary acidic protein, epithelial membrane antigen, or keratin. Ultrastructurally, the cells constituting the hemangiopericytomatous areas had the features of pericytes, and no lipoblasts or transitional forms between lipocytes and pericytes were found. The histologic differential diagnosis of this neoplasm includes spindle-cell lipoma, angiolipoma, liposarcomas, tumors showing smooth muscle and adipocytic differentiation, and hemangiopericytoma infiltrating fat. Because of the small number of cases and the limited follow-up, we cannot be certain of their biologic behavior, although we expect that they are benign. Lipomatous hemangiopericytoma represents a distinctive pathologic entity that should be recognized and studied further.