Tumour-induced Osteomalacia Secondary to Intracranial Tumours - Report of 2 Cases.

Tumor induced osteomalacia (TIO) is a paraneoplastic syndrome which is mostly caused by a phosphaturic mesenchymal tumour mixed connective tissue variant (PMTMCT). These tumours do not have any specific site predilection but their presence in cranial compartment is very rare. Two cases of TIO secondary to phosphaturic mesenchymal tumour at the skull base are described ahead, one of which was in the posterior fossa and the other in middle cranial fossa. Early diagnosis and complete excision of PMT is essential in preventing morbidity secondary to osteomalacia. This case report stands distinct in highlighting a rare site of a phosphaturic mesenchymal tumour and the need to keep a high index of suspicion in cases of TIO especially wherein localization of the tumour is unsuccessful.

Malignant phosphaturic mesenchymal tumor with pulmonary metastasis: A case report.

RATIONALE: Phosphaturic mesenchymal tumor (PMT) is a new tumor entity of soft tissue and bone tumor recently accepted by the World Health Organization, which typically causes the paraneoplastic syndrome of tumor-induced osteomalacia (TIO). The majority of PMTs follow a benign clinical course and local recurrence occurs in < 10% of cases, malignant PMTs with distant organ metastasis are extremely uncommon. PATIENT CONCERNS: We reported a 41-year-old woman who was diagnosed with PMT 10 years ago with a repeated recurrence and pulmonary metastasis. DIAGNOSES: Based on clinical manifestations, MRI scan, serum biochemical indicators evaluation, followed by histopathological examination, the patient was diagnosed as malignant PMT with pulmonary metastasis. INTERVENTIONS: The patient was treated with calcium, phosphorus, and vitamin D after surgical resection and measured the serum ion concentrations every 3 months. OUTCOMES: The patient had a favorable outcome for 10 months without recurrence. LESSONS: PMTs lack of characteristic histological morphology, some recurrence cases may appear benign morphologically; the malignant PMTs are easily overlooked. Patients with PMT should be carefully evaluated and monitored, in order to early identify its malignant potential.

Phosphaturic mesenchymal tumor, nonphosphaturic variant, causing fatal pulmonary metastasis.

Phosphaturic mesenchymal tumors of the mixed connective tissue type (PMT-MCTs) are rare neoplasms, most of which are benign and cause tumor-induced osteomalacia because of overproduction of a phosphaturic hormone, fibroblast growth factor 23 (FGF23). This entity may have been unrecognized or misdiagnosed as other mesenchymal tumors, such as giant cell tumor, hemangiopericytoma, and osteosarcoma. Ten percent of these tumors, without phosphaturia, were diagnosed only by their histologic features. We report here the first case of malignant PMT-MCT, nonphosphaturic variant, resulting in fatal multiple lung metastases. Chondromyxoid matrix with "grungy" calcification, multinucleated giant cell proliferation, and expression of FGF23 mRNA (reverse transcription-polymerase chain reaction) and fibroblast growth factor 23 protein (immunohistochemistry) were seen in the primary and recurrent tumors of the right foot. The lung metastases showed flocculent calcification and FGF23 protein expression as well as giant cell proliferation. This unique case highlights the need for careful histologic assessment of PMT-MCTs, especially the nonphosphaturic variant, and the need for recognition of its rare malignant behavior.

Malignant mesenchymoma of the heart base in a dog with infiltration of the pericardium and metastasis to the lung.

A 9-year-old male rottweiler was presented with abdominal distension, ascites and respiratory distress and marked bulging in the perineal region. At necropsy examination the animal had profuse ascites and hydropericardium and a multinodular mass in the right auricle of the heart infiltrating the epicardium and pericardium and metastasizing to the caudal lobe of the left lung. Microscopically and immunohistochemically the tumour was composed of neoplastic cells with muscular, cartilaginous and adipose differentiation. A diagnosis of malignant mesenchymoma with leiomyosarcomatous (≈ 50%), rhabdomyosarcomatous (≈ 30%), chondrosarcomatous (25%) and liposarcomatous (5%) components was made. Metastatic malignant mesenchymoma has not been reported previously at this site in the dog.

DOG1 antibody in the differential diagnosis of gastrointestinal stromal tumors: a study of 1840 cases.

Gastrointestinal stromal tumors (GISTs), KIT or platelet derived growth factor receptor alpha (PDGFRA) signaling driven mesenchymal tumors of the gastrointestinal (GI)-tract and abdomen, require a precise diagnosis so that the patients may benefit from the newly introduced tyrosine kinase inhibitor drugs. The limitations of the current main tools, KIT immunohistochemistry and KIT/PDGFRA mutation analysis, include lack of KIT expression and mutations in some GISTs. In this study we examined 1168 GISTs of different sites and histologic subtypes, and 672 other tumors and normal tissues for discovered on GIST-1 (DOG1) clone K9, a newly introduced immunohistochemical marker, a chloride channel protein. All GISTs and selected non-GISTs were independently evaluated for KIT. In the GI tract, Cajal cells and gastric surface epithelia were DOG1-positive. The overall sensitivity of DOG1 and KIT in GISTs was nearly identical: 94.4% and 94.7%, and results in GISTs were generally concordant. Gastric spindle cell GISTs was nearly uniformly positive for both markers, whereas DOG1 performed slightly better in gastric epithelioid GISTs that included PDGFRA mutant GISTs. In the intestinal GISTs, KIT was slightly more sensitive than DOG1. Negativity for both DOG1 and KIT was observed in 2.6% of GISTs of GI tract. KIT or PDGFRA mutations were detected in 11/24 DOG1-negative GISTs supporting the diagnosis of GIST. DOG1 expression was also generally present in extragastrointestinal and metastatic GISTs. DOG1 was highly specific for GIST, but exceptional DOG1-positive other mesenchymal tumors included uterine type retroperitoneal leiomyomas, peritoneal leiomyomatosis, and synovial sarcomas (positive in 5/42, 4/17, and 6/37 cases). Leiomyomas colonized by DOG1-positive Cajal cells should not be confused with GISTs. DOG1 positivity was relatively common in esophageal squamous cell and gastric carcinomas, whereas it was rare in colorectal carcinomas. DOG1 should be added into the diagnostic panel evaluating GI and other abdominal tumors, but limitations in its sensitivity and specificity should be recognized.

KIT codon 558 insertions in gastrointestinal stromal tumors. Analysis of 17 rare KIT mutants.

Gastrointestinal stromal tumors are the most common mesenchymal neoplasms of gastrointestinal tract often driven by oncogenic KIT exon 11 mutations. Although deletions and substitutions are most frequent KIT exon 11 mutations, duplications and insertions have been reported as well. In contrast to duplications, which cluster in 3'KIT exon 11, insertions affect 5'KIT, particularly codon 558. Clinicopathologic profile of gastrointestinal stromal tumors with insertions in codon 558 is not known. In this study, 17 gastrointestinal stromal tumors with codon 558 insertions are reported. Fifteen (88.2%) KIT codon 558 insertions consisted of 1694_1695insTCC leading to Lys558delinsAsnPro. However, 2 variant mutants Lys558delinsAsnGln and Lys558delinsAsnAsn were also identified. Based on analysis of inserted and flanking sequences, the insertions contain inverted DNA sequences of the opposite strand. Therefore, these insertions may develop due to a DNA strand switch during replication by DNA polymerases and by the effects of several different DNA repair processes. Patient median age was 61 years, and male-to-female ratio was 1:1.8. gastrointestinal stromal tumors were diagnosed in stomach (n = 4), small intestine (n = 7), and rectum (n = 3). Three tumors were disseminated and primary location could not be established. Fourteen tumors had spindle cell morphology, and epithelioid cell features were seen in 2 intestinal and 1 disseminated gastrointestinal stromal tumor. Based on size and mitotic activity, 2 (50%) of 4 gastric and 3 (48.9%) of 7 small intestinal gastrointestinal stromal tumors had more than 50% risk of metastases according to previous studies of gastrointestinal stromal tumor prognosis. All 3 rectal gastrointestinal stromal tumors were malignant. Metastases were verified in 8 (66.7%) of 12 patients with known clinical and follow-up data. In summary, KIT codon 558 insertions are rare mutations accounting for less than 1% of all KIT mutants. Gastrointestinal stromal tumors with these mutations appear to have predilection to female patients and intestinal location. Moreover, KIT codon 558 insertions might indicate an increased risk of malignant behavior for gastric gastrointestinal stromal tumors.

Syndromic presentation of a pleuropulmonary blastoma associated with congenital cystic adenomatoid malformation. A case report.

Pleuropulmonary blastoma (PPB) is a rare malignant mesenchymal pediatric tumor with a well-recognized association with congenital cystic adenomatoid malformation (CCAM). Recently, it has been described in a patient with CCAM, multiple jejunal polyps, and cystic nephroma. We describe a similar case of a unique presentation of PPB, arising in association with CCAM and with a history of intussception caused by multiple small bowel polyps.

Gastrointestinal stromal tumors of the jejunum and ileum: a clinicopathologic, immunohistochemical, and molecular genetic study of 906 cases before imatinib with long-term follow-up.

Gastrointestinal (GI) stromal tumors (GISTs), the specific KIT- or PDFGRA-signaling driven mesenchymal tumors, are the most common mesenchymal tumors of the GI tract. This study analyzed 1091 tumors originally classified as smooth muscle tumors of the small intestine (including jejunum or ileum and excluding duodenum), and found that 906 (83%) of these were GISTs. The GIST patients had 55:45 male-to-female ratio with a median age of 59 years (range, 13-94 years). Only 0.6% of tumors occurred before the age of 21 years and 13.6% before the age of 40 years. The tumors varied from 0.3 to 40 cm (median, 7.0 cm) and most commonly presented with GI bleeding or acute abdomen; 18% were incidentally detected. Histologically, the tumors were relatively monotypic with spindle cell (86%), epithelioid (5%), or mixed patterns (9%). Skeinoid fibers were present in 44% of cases, and their presence was associated with a favorable course. Most epithelioid tumors were malignant, and this morphology sometimes emerged from less cellular and less mitotically active spindle cell tumors, suggesting that it represented a transformation. KIT was immunohistochemically detected in 98%, CD34 in 40%, smooth muscle actin in 34%, desmin in 0.2%, and S-100 protein in 14% of the tumors tested. Outcome was strongly dependent on tumor size and mitotic activity, with an overall 39% tumor-related mortality, twice that for gastric GISTs. Only <3% of tumors <5 cm and < or = 5 mitoses/50 HPF metastasized, whereas 86% of tumors >10 cm and >5 mitoses/50 HPF metastasized. In stark contrast to corresponding gastric tumors, tumors >10 cm with mitotic activity < or = 5/50 HPF and those < or = 5 cm with mitoses >5/50 HPF had a high metastatic rate (>50%); tumors >5 cm < or = 10 cm with low mitotic rate had a 24% metastatic rate. The median survival times of patients with low mitotic rate tumors who died of disease decreased by increasing tumor size. KIT exon 11 mutations were detected in 90 cases, exon 9 mutation in 17 cases, and exon 17 mutation in 1 case; the presence of mutation or mutation type was not prognostically significant. There were no PDGFRA exon 12 or 8 mutations. Systematic data on prognosis of small intestinal GISTs of various size and mitotic activity categories can be helpful in management and surveillance of patients with these tumors.

Secondary localisation of an intra-thoracic benign mesenchymoma in the fossa poplitea: a rare paediatric case.

Thymomas are tumours that rarely occur in children, are almost invariably benign, and are usually discovered incidentally in the anterior mediastinum on chest X-rays. Whereas in adults these tumours are often associated with myasthenia gravis and other autoimmune diseases, this occurrence is very rare in the paediatric population. Multiple localisation and/or extra-thoracic recurrence of thymomas in children also appears to be exceptional with no reported cases in the English literature. We report one rare paediatric case.

PKC theta, a novel immunohistochemical marker for gastrointestinal stromal tumors (GIST), especially useful for identifying KIT-negative tumors.

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor in the digestive tract and the majority of GIST has characteristic gain-of-function mutations of the c-kit gene, which encodes the KIT receptor for stem cell factor. The present study aimed to establish the usefulness of protein kinase C theta (PKC theta) as an immunohistochemical marker for GIST in comparison with KIT immunohistochemistry. PKC theta immunohistochemistry was carried out not only on 48 cases of GIST and another 40 cases of gastrointestinal mesenchymal tumors, but also on 24 cases of various tumors known to be immunohistochemically positive for KIT. Immunohistochemically, 41 out of 48 cases (85%) of GIST were positive for PKC theta, and its expression was confirmed by Western blot analysis using six cases of surgically resected GIST. In the present study there were six GIST immunohistochemically negative for KIT, which histologically revealed a myxoid epithelioid appearance characteristic to that of GIST with platelet-derived growth factor receptor alpha mutation. All six GIST were immunohistochemically positive for PKC theta. No PKC theta immunoreactivity was observed in other gastrointestinal mesenchymal tumors and various KIT-positive tumors except for three cases (14%) of gastrointestinal schwannomas. The present study revealed that PKC theta is an immunohistochemically novel and useful marker for GIST, especially for GIST negative for KIT.

Cytological features of epithelioid mesenchymal neoplasms: a study of 21 cases.

Epithelioid mesenchymal neoplasms (EMNs) are rare tumors that share cytological, histological, and immunohistochemical features with epithelial tumors. It is important to distinguish EMNs from epithelial tumors in cytology specimens due to their different clinical management and prognosis. The cytomorphological features of histologically confirmed EMN were reviewed. Twenty-one cytological specimens of EMN were evaluated and characterized by polygonal cells with moderate to abundant dense cytoplasm, prominent nucleoli, and pleomorphism. Additional findings included the presence of a distinct population of spindle cells, hemosiderin-containing cells, multinucleated cells, and granuloma-like structures in selected cases. Cytokeratin immunoreactivity was seen in two cases and was negative in one case. This study shows that the cytological features of EMNs and epithelial tumors overlap; nonetheless, some features are more helpful in suggesting EMN. A panel of immunocytochemical studies must include specific mesenchymal markers to avoid a misdiagnosis of carcinoma in cases of cytokeratin-positive EMN.

Evaluation of malignancy using Ki-67 labeling index for gastric stromal tumor.

BACKGROUND: Assessment of malignant potential in gastrointestinal stromal tumors (GISTs) is still problematic. The maximum tumor diameter and the mitotic index are generally used as an index of malignancy of GISTs. The Ki-67 labeling index has recently been used as an index of cell growth, and the prognosis of GISTs was reported to be significantly poor when the value of this index was 10% or higher. METHODS: Clinicopathological and immunohistological factors were analyzed in 15 patients who underwent surgical resection of gastric stromal tumors at our department between April 1997 and July 2002. The patients were divided into "metastasis/recurrence" and "benign" groups. Also, the relationship of changes in the Ki-67 labeling index to the degree of malignancy in recurrent lesions was assessed in an 84-year-old woman who underwent five reoperations because of recurrences in the peritoneum. RESULTS: Significant differences were noted between the metastasis/recurrence and benign groups in relation to the mean maximum tumor diameter (186.7 +/- 80.8 mm vs 41.3 +/- 22.9 mm), mitotic index (88.3 +/- 5.0/50 high-power fields [HPF] vs 3.0 +/- 2.9/50 HPF), and the Ki-67 labeling index (11.4 +/- 2.5% vs 0.01 +/- 0.51%). In the patient who had metastasis to the liver 3.5 years after initial operation and underwent five reoperations before death, the intervals until detection of recurrence tended to be shortened gradually. The Ki-67 labeling index varied with each operation, and tended to be higher at the time of reoperations than at the initial operation. CONCLUSION: The maximum tumor diameter, mitotic index, and Ki-67 labeling index were useful as an index of malignancy for gastric stromal tumor. The efficacy of surgical resection alone may be insufficient in patients with disseminated metastasis to the peritoneum.

Frequent occurrence of low grade cases among metastatic gastrointestinal stromal tumours.

AIM: Gastrointestinal stromal tumours (GISTs) are uncommon mesenchymal neoplasms. Some metastasise, whereas others remain asymptomatic for years, but it is difficult to distinguish between them histologically. This report analyses the characteristics of seven metastasising GISTs and compares clinicopathological parameters of the metastatic and non-metastatic groups. METHODS/RESULTS: Histology revealed typical GIST features with spindle, epithelioid, or mixed appearance. All seven cases were positive for vimentin, five for neurone specific enolase, six for c-kit, four for S-100, three for PGP-9.5, three for CD-34 and synaptophysin, but all were negative for cytokeratin, neurofilament, chromogranin A, and desmin. Four showed a focal reaction for smooth muscle actin. Three of the tumours were GI, and two each were GII and GIII. The Ki-67 index varied from 4% to 44%, the three GI cases had 4%, 10%, and 16%. Tumours from the metastatic GIST group were significantly larger than those from the non-metastatic group. CONCLUSIONS: Three cases exhibited bland, GI histological features with moderate or low proliferative activity. Among the c-kit positive metastasising stromal tumours, some were low grade, with moderate or low mitotic and Ki-67 indices, emphasising the necessity to develop a reliable grading system for GIST to predict clinical behaviour, the importance of careful analysis of "benign looking" tumours, and the key role of c-kit status in identifying patients who could benefit from treatment with STI-571. Larger tumours had a higher chance of metastasising, and only the size of the primary tumour played a role in predicting metastatic potential.

Fine-needle aspiration cytology and immunocytochemistry in the diagnosis of 24 gastrointestinal stromal tumors: a quick, reliable diagnostic method.

The diagnosis of gastrointestinal stromal tumors (GISTs) is generally established on histopathologic examination of surgical specimens. Fine-needle aspiration (FNA), performed under the guidance of ultrasound or computed tomography, is being used with increasing frequency in an attempt to diagnose primary and/or metastatic GISTs before surgery. The present study was undertaken to characterize the cytological appearance of these tumors and to assess the role of cytology, together with immunocytochemistry (ICC), in the diagnosis of GISTs. Twenty-four GISTs diagnosed by FNA cytology at our institution have been reviewed. Immunocytochemical studies with c-kit and CD34 were performed in all cases on current or archival Papanicolaou-stained smears. All cases stained with c-kit, and 19 reacted with CD34. Cytomorphology and immunocytochemical characteristics are discussed. Our results confirm the utility of FNA together with ICC in the diagnosis of primary and/or metastatic GISTs.

Complete remission of a metastatic gastrointestinal stromal tumour with the tyrosine kinase inhibitor imatinib (STI 571): effect of low dosage in an advanced tumour with exon 11 mutation.

We report a 51-year-old man with an advanced malignant metastatic gastrointestinal stromal tumour, who showed a complete response after 5 months of treatment with imatinib at a dose of 400 mg per day. An early treatment response was demonstrated in an 18fluorodeoxyglucose positron emission tomography scan after 1 month of therapy. Complete remission was documented histologically by negative serial biopsies of residual tumour nodes after 5 months of therapy. No serious side effects were seen with imatinib. A 21 bp, exon 11, in-frame mutation of the c-kit gene was found by DNA sequence analysis of tumour tissue.

Malignant mesenchymoma of the uterus, arising in a leiomyoma.

AIMS: To document and find evidence for the rare occurrence of malignant progression of a benign uterine leiomyoma with divergent mesenchymal differentiation. In a 54-year-old female a large pedunculated tumour was encountered which had suddenly increased in size and had apparently arisen at the site of a subserosal uterine leiomyoma first described 19 years earlier. The tumour seemed histologically diverse in its composition. The possibility of malignant progression of the benign leiomyoma with divergent mesenchymal differentiation was entertained. METHODS AND RESULTS: In the resected tumour, smooth muscle, osseous and adipose components were identified and these were assessed using recognized histological criteria of malignancy. In addition to a benign smooth muscle component, malignant leiomyosarcomatous tissue was seen in addition to a malignant osseous component and a malignant adipose component. The tumour thus met the criteria of a malignant mesenchymoma. The relationship of the different components of the tumour was analysed by immunohistochemistry and with molecular loss of heterozygosity (LOH) analysis. In the osseous and leiomyosarcomatous components a similar LOH pattern was observed. The adipose component showed a distinct LOH pattern. Retention of smooth muscle differentiation in the osseous component was demonstrated by desmin immunostaining. CONCLUSION: Malignant transformation of benign uterine leiomyoma may rarely occur. Mesenchymal stem cells underlying these tumours may show divergent mesenchymal differentiation.

Disseminated malignant ectomesenchymoma (MEM): case report and review of the literature.

Malignant ectomesenchymoma (MEM) is a rare soft tissue tumor believed to arise from a pluripotent migratory neural crest cell and composed fo both a mesenchymal element and a neuroectodermal element. The authors report the case of an 11-month-old male who presented with a local abdominal MEM and systemic metastases into lungs, liver, bones, and bone marrow. This is the first reported case of an MEM with initial bone marrow dissemination. The tumor consisted of a neuroblastoma component and a mesenchymal component with sarcomatous features. Diagnosis and therapy were complicated by the histological heterogeneity of the tumor, which also influenced the clinical appearance and course in this case. A literature search revealed 15 other evaluated cases that arose in soft tissue and had adequate clinicopathologic data. Complete surgical resection was the mainstay of treatment, and chemotherapy also appeared to be important. In all reported patients (n = 3) with initial metastases or bone marrow dissemination, as in this case, no cure could be achieved. In patients with disseminated MEM, new therapeutic approaches such as high-dose chemotherapy followed by stem cell rescue should be considered, similar to the current strategy in patients with stage VI neuroblastoma or soft tissue sarcoma.

Rhabdomyosarcoma metastasizing as a malignant ectomesenchymoma.

Rhabdomyosarcoma is a common childhood malignancy that may occasionally occur as a component of a mixed mesenchymal tumor, e.g., a triton tumor or malignant ectomesenchymoma. A case is reported of a 13-year-old boy who had resection of a paratesticular embryonal rhabdomyosarcoma with subsequent radiation and chemotherapy. Two years later, a retroperitoneal metastasis was resected. Histology showed a mixture of rhabdomyoblasts, ganglion cells, and a third population of cells with combined features of these two distinct cell types. Electron microscopy confirmed the presence of rhabdomyoblasts with characteristic bundles of myofilaments and Z-band material, and ganglion cells with prominent nuclei and nucleoli, rough endoplasmic reticulum, dense core granules, filaments, and tubules. Notably, the third cell population showed features of both rhabdomyoblasts and ganglion cells. Immunohistochemistry confirmed the mixed population of rhabdomyoblasts (positive for vimentin, desmin, negative for S-100, NSE), ganglion cells (positive for S-100 and NSE, negative for vimentin and desmin), and the third population expressing all test antigens. The features of this metastatic lesion are those of a malignant ectomesenchymoma with combined rhabdomyosarcoma and ganglioneuroma components. It is postulated that this lesion results from biphenotypic expression of tumor cells that previously expressed only rhabdomyoblastic differentiation. The role of prior chemotherapy and radiotherapy in this particular case is unclear.