Origin of selective inhibition of mitochondrial complex I by pyridinium-type inhibitor MP-24

Positively charged pyridiniums are unique inhibitors to probe the structural and functional properties of the ubiquinone reduction site of bovine heart mitochondrial complex I. In this study, we synthesized a series of neutral as well as pyridinium analogues of MP-24 (N-methyl-4-[2-methyl-2-(p-tert-butylbenzyl)propyl]pyridinium), a selective inhibitor of one of the two proposed binding sites of these pyridinium-type inhibitors of complex I (H. Miyoshi et al., J. Biol. Chem. 273 (1998) 17368-17374), to elucidate the origin of its selectivity. Inhibitory potencies of all neutral and pyridinium analogues with tetraphenylboron (TPB(-)), which forms an ion-pair with pyridiniums, were comparable, although the degrees of selective inhibition by pyridiniums without TPB(-) were entirely different. In contrast to MP-24, the dose-response curves of nonselective pyridiniums and all neutral analogues were not affected by incubation conditions. These results strongly suggested that the process of the inhibitor passage to the binding sites is responsible for the selective inhibition.

Ultrastructure of Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8 (HHV-8) in a primary effusion lymphoma cell line treated with tetradecanoyl phorbol acetate (TPA)

The ultrastructure of Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8 (HHV-8) has not yet been fully elucidated, although some findings have been reported using primary effusion lymphoma (PEL) cell lines, KS-1, harboring no Epstein-Barr virus (EBV) coinfection. In the present study, detailed fine structural examination of KSHV/HHV-8 was performed after stimulation of the PEL-derived cell line KS-1 with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) in vitro. While unstimulated KS-1 cells contained a small number of intranuclear virus particles associated with no extracellular mature particles, KS-1 cells stimulated with TPA produced many extracellular mature particles as well as intranuclear particles, in addition to interesting tubulo-reticular structures and aggregated tubular structures in vesicles. The induced intranuclear particles were empty, doughnut shaped, and dense cored, with outer and inner diameters of 100-110 nm and 60-70 nm, respectively. Dense-cored extracellular mature particles were 150-160 nm in diameter, and some contained doughnut-shaped cores, together with a few megaloviruses, 260 nm in outer diameter. These findings indicate that KS-1 cells treated with TPA can produce extracellular mature particles as well as intranuclear particles, which were proven to be KSHV/HHV-8.

A new human synovial sarcoma cell line, HS-SY-3, with a truncated form of hybrid SYT/SSX1 gene

Recent cytogenetical and molecular studies have indicated that synovial sarcoma harbors a t(X;18)(p11.2;q11.2) translocation, resulting in the formation of a hybrid SYT/SSX (SSX1 or SSX2) gene. We newly established a human cell line, HS-SY-3, from a synovial sarcoma. HS-SY-3 cells were shown to harbor the pathognomonic t(X;18)(p11.2;q11.2) translocation by chromosome analysis but not to exhibit the classical hybrid SYT/SSX transcripts induced by this translocation, using RT-PCR. To determine the reason for this discrepancy, we analyzed cDNA from HS-SY-3 cells, as well as the original sarcoma tissue by the rapid amplification of cDNA 3' end assay, and found that the chimaeric cDNA was 240 bp shorter than the previously established SYT/SSX1 cDNA due to truncation of the 3' side of SSX1. The HS-SY-3 cells should be useful for future functional studies of the SYT/SSX chimeric gene.

Overexpression of c-Met protein in human thyroid tumors correlated with lymph node metastasis and clinicopathologic stage

To examine the expression of c-Met protein in thyroid tumors and the correlation of c-MET protein expression with lymph node metastasis (LNM) and pathological stage, 111 papillary thyroid carcinomas (PTC), including 44 with synchronous LNM, and 117 follicular adenomas (FA) were immunohistochemically examined using dewaxed sections of formalin-fixed, paraffin-embedded tissues. Immunohistochemical results were confirmed by Western blot analysis. For PTC, positive immunostaining was observed in 107 of 111 (96.4%) cases and was diffusely present in either cytoplasm and nucleus, or only cytoplasm or only nucleus of cancer cells at varying intensities. Staining tended to be stronger in the periphery of cancer cell nests. Positive reaction was also found in 44 of 117 (37.6%) cases of FA. However, the extent and intensity of c-Met immunostaining in FA were far less than those in PTC (p < 0.0001). Forty-four PTC cases (39.6%) exhibited LNM, and the extent and intensity of c-Met expression were significantly correlated with both LNM (p < 0.0001) and pathological stage (p < 0.0001). No significant correlation of c-Met expression with age, sex or tumor size was found. Our findings suggest that PTC expresses c-Met protein much more strongly and intensively than does FA, and that strong and intense overexpression of c-Met protein may be an indicator of the presence of lymph node metastasis and advanced pathological stage of papillary thyroid carcinoma.

Pigmented squamous cell carcinoma of the scrotum associated with a lentigo

Only 13 cases of pigmented squamous cell carcinoma (SCC) have been reported in the English language literature, with most frequent development in the oral cavity and conjunctiva. However, no case of pigmented SCC of the scrotum has been reported. We report here a case of pigmented SCC that arose primarily in the scrotum of a 70-year-old man. Light microscopically, this tumour exhibited the typical features of a pigmented SCC, including not only keratinization and intercellular bridges but also colonization by plump dendritic melanocytes with marked pigmentation. These features were clearly confirmed by immunohistochemistry, including strong positivity of tumour cells for high-molecular-weight cytokeratin and of colonizing melanocytes for HMB-45. The tumour was associated with a lentiginous lesion and partly involved it. Melanocytes entrapped from the lentigo might therefore have been activated during enlargement of this tumour, resulting in melanocyte colonization. Fourteen cases of pigmented SCC, including ours, are clinicopathologically reviewed.

Endometrial stromal sarcoma with clonal complex chromosome abnormalities. Report of a case and review of the literature

Only eleven endometrial stromal sarcomas (ESS) with clonal chromosomal abnormalities have been reported in the literature. Of these, four have been reported to harbor the t(7;17) translocation. We report here an additional ESS that exhibited clonal complex chromosome abnormalities not described earlier: 38,XX,-1,del(1)(q11),-2,add(2)(p13),-3,der(4)add(4)(p12)psu dic(4;14)(q35;q11.2), add(6)(p21.3),add(7)(q22),del(7)(p11.2p13),-8,-9,add(9)(q34),- 10,add(10)(q24),-11,-11,ins(12;?) (q13;?),-14,-14,-15,ins(15;?)(q22;?),add(16)(q22),add(17)(q11.2),- 18,der(18)t(7;18)(q11.2;p11.2),-19, add(20)(p13),add(21)(p11.2),-22,add(22)(p11.2),+6mar in metaphase cells from primary short-term culture.

Method of lymphocytotoxic crossmatch test for feline renal transplantation

The optimal condition for methods of lymphocytotoxic crossmatch test for feline renal transplantation was investigated. On separation of viable lymphocytes from whole blood, the best results were obtained when Ficoll-diatrizoate with 1.078 of a specific gravity at 20 degrees C was centrifuged with 800 x g for 30 min at 4 degrees C. A nylon wool column was used to separate T and B cells from lymphocyte fraction. The ratio of T cells in nylon wool effluent cells was 95%, while the ratio of B cells in adherent cells was 41%. Lymphocytotoxic crossmatch tests were performed by using the effluent cells as T cells and the adherent cells as B cells, at 37 degrees C (warm) and 4 degrees C (cold). The ratio of B cells in adherent cells was low, however, the result was utilized as a matching test before transplantation by combining with the T cell result. The trypan blue stain method made it easier than the eosin stain method to distinguish living and dead cells. The lymphocytotoxic crossmatch tests were performed on 15 pairs of healthy cats, and only one pair showed doubtful positive against anti-B cell cold antibodies. During acute rejection after renal transplantation in two pairs which were negative on any anti-lymphocyte antibodies before the transplantation, the anti-T cell warm antibodies became positive in both pairs, and the anti-T cell cold antibodies became positive on one of the two pairs.

Further characterization of the human clear cell sarcoma cell line HS-MM demonstrating a specific t(12;22)(q13;q12) translocation and hybrid EWS/ATF-1 transcript

Only a small number of clear cell sarcoma (CCS) cell lines have been reported, including the cell line HS-MM. In the present study, this cell line, maintained for more than 4 years since establishment, was further characterized by cytogenetic studies, fluorescence in situ hybridization (FISH) analysis, and reverse transcriptase-polymerase chain reaction (RT-PCR). HS-MM cells both in vitro and in vivo exhibited pseudodiploid karyotypes with the specific t(12;22)(q13;q12) translocation. The translocation between chromosomes 12 and 22 was confirmed by FISH analysis and the hybrid EWS/ATF-1 transcript induced by this translocation was detected by RT-PCR. The HS-MM cell line will be useful for further studies of CCS.

Dermatofibrosarcoma protuberans harboring t(9;22)(q32;q12.2)

More than 20 cases of dermatofibrosarcoma protuberans (DFSP) exhibiting chromosomal abnormalities have been reported. Approximately three fourths of these tumors have harbored supernumerary ring chromosomes, which have been suggested to be specific for this tumor. However, a small number of DFSPs with translocations such as t(2;17), t(X;7), and t(17;22) have recently been reported. We report a DFSP arising in a 23-year-old woman which unexpectedly exhibited the balanced translocation, t(9;22)(q32;q12.2) as the only anomaly with G-band technique. Dual-color fluorescence in situ hybridization (FISH) confirmed these cytogenetic findings. Similar to that previously reported for DFSPs with translocations, the present tumor also lacked ring chromosomes.

Nephrogenic adenoma of the bladder in a chronic hemodialysis patient

BACKGROUND

Nephrogenic adenoma is an uncommon, benign metaplastic lesion occurring in the urothelium, usually as a response to chronic irritation or trauma. It is rarely encountered in hemodialysis patients. Endoscopically, these lesions can easily be mistaken for malignant tumors.

METHODS/RESULTS

We report on a case of nephrogenic adenoma of the bladder in a chronic hemodialysis patient that was large and mistakenly diagnosed as transitional cell carcinoma in the initial biopsy. Histopathological examination of the total cystectomy specimen demonstrated the correct diagnosis of nephrogenic adenoma.

CONCLUSION

Increased awareness by urologists and pathologists of nephrogenic adenoma may lead to its more accurate diagnosis.

Inflammatory pseudotumor of the urinary bladder with aberrant expression of cytokeratin. Report of a case with cytologic, immunocytochemical and cytogenetic findings

BACKGROUND

Cytologic descriptions of inflammatory pseudotumor of the urinary bladder are exceedingly rare. We describe here an additional case of this disease, including its cytologic features and aberrant expression of cytokeratin.

CASE

A 35-year-old male presented with gross hematuria but no history of bladder surgery. Urine cytology revealed a few atypical spindle cells suspicious for sarcoma. Histologically, the lesion consisted of spindle cells of various sizes and shapes, proliferating in irregularly running bundles, but no severe nuclear atypia or pathologic mitosis was found. Immunocytochemically, these cells were unexpectedly positive for cytokeratin as well as for vimentin and muscle actin. All metaphase cells examined revealed a normal male karyotype.

CONCLUSION

Inflammatory pseudotumor must be distinguished in particular from leiomyosarcoma and spindle cell carcinoma. To avoid an erroneous diagnosis, recognition of this entity is important, together with careful histologic examination and awareness of the possible aberrant expression of cytokeratin.

Sun-exposure- and aging-dependent p53 protein accumulation results in growth advantage for tumour cells in carcinogenesis of nonmelanocytic skin cancer

Three hundred and sixteen patients with nonmelanocytic skin cancer, including 46 cases of Bowen's disease (BOD), 134 cases of squamous cell carcinoma (SCC), and 136 cases of basal cell carcinoma (BCC), were examined immunohistochemically using monoclonal antibody DO-7 to assess p53 protein accumulation related to sun exposure and ageing, and growth and differentiation of skin cancer and its precursors. The rates of p53 immunostaining of BOD, SCC and BCC were 80.4%, 76.1% and 70.6%, respectively. p53-positive cells were present not only in cancer nests, but also in dysplastic and even morphologically normal epidermis adjoining cancers. Sun exposure was statistically correlated with the p53 immunostaining scores in morphologically normal epidermis of the three skin cancers and in cancer nests of SCC and BCC. The positivity and score of p53 protein often differed significantly among the three types of cancer, especially in regions of dysplasia. Interestingly, differentiation of SCC was correlated with individual p53 scores for dysplasia and cancer nests, especially for dysplasia. BOD, as the precursor of SCC, demonstrated the strongest p53 expression. Furthermore, 12.3% cases with p53 negative cancer nests showed p53-positive reaction in dysplasia and in morphologically normal epidermis. It seems that the accumulation of p53 protein plays a part in precancerous lesions and in the genesis of more highly differentiated types of skin cancer and affects mainly the growth of tumour cells rather than their differentiation. For BCC, however, age was significantly related to p53 expression. Our findings suggest that overexpression of p53 in normal skin and cancer nests of SCC and BCC is significantly related to sun exposure, that the expression of p53 in BCC is an age-dependent process, and that the early accumulation of p53 protein may be a useful predictor for the detection of nonmelanocytic skin cancer.

Primary ovarian angiosarcoma: a case report and literature review

Primary ovarian angiosarcoma is extremely rare. Only 16 cases have histologically been reported to date in the literature. A case of angiosarcoma arising in the right ovary of a 46-year-old female is presented. Grossly, the resected right ovary was completely replaced by a solid tumor mass, which revealed multiple necrotic and/or hemorrhagic foci. This case revealed the typical histological features of angiosarcoma with sinusoidal and solid patterns of anaplastic tumor cells. Immunohistochemically, tumor cells were strongly and diffusely positive for CD31 and CD34, in particular, along the cytoplasmic membrane of the tumor cells. Ultrastructurally, tumor cells possessed the intermediate junctions between tumor cells, discontinuous basal laminae attached to the irregularly shaped blood vessels and occasional cytoplasmic pinocytotic vesicles. These findings confirmed the case as being one of angiosarcoma of the ovary. The patient died 9 months after surgery as a result of developed multifocal brain metastases. A total of 17 cases reported as primary ovarian angiosarcoma, including this presented case, are clinicopathologically reviewed.

Osteoclast-like giant cell tumor of the pancreas with metastases to gallbladder and lymph nodes. A case report

Osteoclast-like giant cell tumor of the pancreas (OGTP) is a rare neoplasm, of which the histogenesis is still controversial. Here we report a case of OGTP involving the head of the pancreas in a 71-year-old woman with metastases to the gallbladder and lymph nodes. The primary and metastatic tumors had identical histopathological, immunohistochemical, ultrastructural and molecular biological features. Microscopically, the tumors were characterized by atypical, often pleomorphic mononuclear cells associated with the proliferation of benign-appearing osteoclast-like giant cells (OGCs). Electron microscopic observation provided ultrastructural evidence of epithelial differentiation of the mononuclear cells, including microvilli and desmosomes, which was not obtained for OGCs. On immunohistochemical study, OGCs stained for CD68 (KP-1), LCA and HAM56, whereas mononuclear cells only reacted with PCNA. These findings clearly suggest that mononuclear cells are capable of differentiation and proliferation and may have been the only true tumor cells in this neoplasm, and that OGCs may have been a paraneoplastic product of this rare tumor. On examination of DNA from dewaxed sections of the tumor, we found no p53 mutation in the tumor tissue, but found two K-ras mutations in codon 12; this pattern of mutation commonly occurs in pancreatic carcinoma, indicating a somewhat genetic relationship of OGTP to pancreatic carcinoma. Although OGTP often has a favorable prognosis, the outcome in the present case was poor due to early tumor spread, with less than two years postoperative survival.

Malignant granular cell tumor: report of a case and review of the literature

The histological, immunohistochemical and electron microscopic features of a rare malignant granular cell tumor (GCT) arising in the left radial nerve of a 54-year-old man are reported. Despite a lack of local recurrence following extirpation, the tumor metastasized to the skull five years later. Light-microscopically, both primary and metastatic tumors consisted of markedly atypical or pleomorphic neoplastic cells with abundant cytoplasm containing diastase-resistant periodic acid Schiff reaction-positive granules. These tumor cells were arranged in a sheet-like pattern with mitotic figures including atypical ones, and were frequently immunopositive for proliferating cell nuclear antigen and c-MET, the c-met proto-oncogene product. These findings reflect high-grade malignancy of the present tumor. In addition, the tumor cells were positive for S-100 protein and neuron-specific enolase. Ultrastructurally, a large number of intracytoplasmic granules featuring secondary lysosomes as well as long interdigitating cytoplasmic processes, intercellular intermediate junctions, discontinuous basal lamina-like structures, and stromal long-spacing collagen were observed. These findings indicated schwannian differentiation of the present tumor. In addition, based on a review of previously reported cases, the overall clinicopathological characteristics of malignant GCT were summarized.

Specificity of pyridinium inhibitors of the ubiquinone reduction sites in mitochondrial complex I

Dual binding sites for pyridinium-type inhibitors in bovine heart mitochondrial complex I have been proposed (Gluck, M. R., Krueger, M. J., Ramsay, R. R., Sablin, S. O., Singer, T. P., and Nicklas, W. J. (1994) J. Biol. Chem. 269, 3167-3174). The marked biphasic nature of the dose-response curve for inhibition of the enzyme by MP-6(N-methyl-4-[2-(p-tert-butylbenzyl)propyl]pyridinium) makes this compound the first selective inhibitor of the two sites (Miyoshi, H., Inoue, M., Okamoto, S., Ohshima, M., Sakamoto, K., and Iwamura, H. (1997) J. Biol. Chem. 272, 16176-16183). Modifications of the structure of MP-6 show that a tert-butyl group on the benzene ring, a methyl group attached to the pyridine nitrogen atom, para-substitution pattern in the pyridine ring, and the presence of a branched structure in the spacer moiety are important for the selective inhibition. On the basis of the structural specificity, we synthesized a selective inhibitor, MP-24 (N-methyl-4-[2-methyl-2-(p-tert-butylbenzyl)propyl]pyridinium), which elicits greater selectivity. Characterization of the inhibitory behavior of MP-24 provided further strong evidence for the dual binding sites model.

Characterization of the ubiquinone reduction site of mitochondrial complex I using bulky synthetic ubiquinones

A wide variety of alkyl derivatives of Q2 (6-geranyl-2, 3-dimethoxy-5-methyl-1,4-benzoquinone) and DB (6-n-decyl-2, 3-dimethoxy-5-methyl-1,4-benzoquinone), in which methoxy groups of the 2- and/or 3-positions of the quinone ring were replaced by other bulky alkoxy groups from ethoxy to butoxy, were prepared by novel synthetic procedures. Electron-accepting activities of the bulky quinones were investigated with bovine heart mitochondrial complex I and its counterpart of Paracoccus denitrificans(NDH-1) to elucidate structural and functional features of the quinone reduction site of the enzymes. The bulky quinone analogues served as sufficient electron acceptors from the physiological quinone reduction site of bovine complex I. Considering the very poor activities of even the ethoxy derivatives as substrates for other respiratory enzymes such as mitochondrial complexes II and III [He, D. Y., Gu, L. Q., Yu, L., and Yu, C. A. (1994) Biochemistry 33, 880-884], this result indicated that the quinone reduction site of bovine complex I is spacious enough to accommodate bulky exogenous substrates. In contrast to bovine complex I, bulky quinone analogues served as poor electron acceptors with Paracoccus NDH-1. These observations indicated that bovine complex I recognizes the substrate structure with poor specificity. The substituent effects in the 2- and 3-positions of the quinone ring on the electron-transfer activity with bovine complex I differed significantly between Q2 and DB series despite having the same total number of carbon atoms in the side chain. The inhibitory effect involving Q2 due to its geranyl side chain was markedly diminished by structural modifications of the quinone ring moiety. These findings indicate that the side chain plays a specific role in the redox reaction and that the quinone ring and side-chain moieties contribute interdependently to binding interaction. Moreover, structural dependency of the proton-pumping activity of the quinone analogues was comparable to that of the electron-transfer activity with bovine complex I, indicating that the mechanism of redox-driven proton-pumping does not differ depending upon the substrate structure.

Adult T cell leukemia/lymphoma with massive involvement of cardiac muscle and valves

An autopsy case of a 58-year-old woman with massive cardiac involvement of adult T cell leukemia/lymphoma (ATLL) is reported. She developed cardiac failure due to aortic and mitral regurgitation with cardiac infiltration of ATLL cells, and underwent replacement of both aortic and mitral valves. Studies of the cut-surfaces revealed diffuse thickening of the subendocardial wall of the left chamber with widespread whitish-brown tumor infiltrates. In the regions surrounding the replaced aortic and mitral valves there was also massive tumor cell infiltration. The tumor cells infiltrating the cardiac muscle wall were T cell in origin and exhibited Leu-3a (CD4)-positive immunoreaction. Ultrastructurally, tumor cells contained markedly indented nuclei and some were attached directly to the muscle cells. These findings suggest that this was an unusual form of ATLL with widespread involvement of the heart.

Ongoing osteolysis in patients with lymphangioma

Severe osteolysis is a rare complication of lymphangioma. It can progress despite treatment and may be fatal. Four patients presented with massive osteolysis and serious related complications. Of these, two responded well to OK-432 therapy with arrest of the osteolysis. Complete recovery from life-threatening pleural effusion has been noted in one. Of the two nonresponders, one died of progressive osteolysis of the cervical and occipital bones, the other, despite therapy, still shows progressive osteolysis of the left leg from the femur to the phalanges. A boneless leg may be the outcome.

Epithelioid sarcoma producing granulocyte colony-stimulating factor

An epithelioid sarcoma of the perineum of a 60-year-old man with widespread metastases produced leukocytosis, myeloid hyperplasia of the bone marrow, and splenomegaly. High titers of granulocyte colony-stimulating factor (G-CSF) were found in the patient's serum and primary culture medium of the tumor tissue. The tumor tissue extract contained m-RNA for G-CSF in large quantities, proving that the tumor was the source of this cytokine.

[A case of chromophobe cell renal carcinoma]

We report a case of chromophobe cell renal carcinoma. A 59-year-old female was admitted to our hospital with asymptomatic gross hematuria. Abdominal computerized tomography showed an approximately 4 cm. minimally enhancing mass in the left kidney. Angiography revealed a hypovascular tumor in the left kidney. Under the diagnosis of renal cell carcinoma, left radical nephrectomy was performed. The cut surface of the tumor was beige in color with few foci of hemorrhage and necrosis. Microscopically, the tumor was composed of the cells with voluminous reticulated cytoplasm stained lightly with routine hematoxylin and eosin. Hale's colloidal iron staining demonstrated a positive cytoplasmic reaction. Pathological diagnosis was chromophobe cell renal carcinoma. Chromophobe cell renal carcinoma is a recently established subtype of renal cell carcinoma, which has rarely been reported in Japan.

Ameloblastoma of the mandible metastasizing to the orbit with malignant transformation. A histopathological and immunohistochemical study

We report here a case of ameloblastoma of the mandible with multiple local recurrences and metastasis to the orbit. The patient was a 63-year-old Japanese woman with visual disturbance of her right eye. Diagnostic imaging revealed a mass occupying the right orbital apex with partial intracranial involvement. She had been surgically treated for mandibular ameloblastoma 27 years previously, and the tumour had recurred three times in the past 5 years. The orbital tumour and recurrent ameloblastomas were investigated histopathologically and immunohistochemically. The tumour changed in morphology as it recurred, from follicular ameloblastoma without atypia to apparent malignant tumours disclosing undifferentiated or squamoid features. On immunohistochemical analysis, staining for cytokeratin was positive in the squamoid cells but not in the undifferentiated cells. Both histopathologically and immunohistochemically, the orbital tumour was almost identical to the undifferentiated recurrent tumour. The orbital tumour was distinct from the primary site or sites of recurrence of ameloblastoma, and we concluded that the mandibular ameloblastoma underwent malignant transformation with multiple recurrences and finally metastasized to the orbit.

Multilocular thymic cysts associated with thymoma. A case report

The association of multilocular thymic cysts (MTC) with thymoma is exceedingly rare, and the pathogenesis of this combination is controversial. We describe the case of a 42-year-old man with an anterior mediastinal mass found to contain MTC and thymoma. A multilocular cystic mass, measuring 13 x 6.5 x 2 cm, was found in the right lobe of the thymus, and contained a 4.7 x 2 cm thymoma in its center. Microscopic thymomas, lipomatously involuted remaining thymic tissue, and lymphoid follicles with germinal centers were found in the walls of MTC as well as in the left thymic lobe. Non-specific chronic inflammation was also present in the walls. In addition, microcysts, which were only found at the periphery of the thymoma and covered with epithelium, might have been formed secondarily by dilatation of the perivascular spaces and of Hassall's corpuscles. These findings suggest that a chronic inflammatory process was responsible for the early formation and enlargement of this patient's MTC, and that while the cavities of the MTC expanded to various degrees, the thymoma, which originated from one of the microscopic thymomas in the walls of MTC, increased in size, and grew to involve the remaining thymic tissue.

[Hyperuricemia in hematological disorders]

Hyperuricemia is a common manifestation in various hematological disorders such as hemolytic anemias, megaloblastic anemia malignant lymphomas and leukemias. Tumor lysis syndrome (TLS) is a serious complication consists of hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcemia due to massive cell lysis, which occurs shortly after the onset of chemotherapy or radiotherapy for acute leukemias and malignant lymphomas. Acute renal failure may develop due to uric acid nephropathy. The risk factors of TLS are heavy tumor cell burden, rapid cell turn over rate and renal involvement of neoplastic cells. To prevent and control TLS, adequate intravenous hydration to keep patient's urine volume, alkalization of urine by sodium bicarbonate and inhibition of uric acid production by high dose allopurinol is recommended.

Desmoplastic malignant melanoma of the gingiva: case report and review of the literature

A rare case of desmoplastic melanoma arising from the maxillary gingiva of a 66-year-old woman is reported. This tumour metastasised to the submandibular lymph node 5 years after extirpation, and local recurrence was observed 2 years later. The gingival tumour showed the histopathological characteristics of desmoplastic melanoma and the metastasised tumour cells were immunohistochemically positive for S-100 protein, neuron specific enolase, HMB-45 highly specific for conventional melanoma, and Fontana-Masson staining. The gingival tumour, originally regarded as benign clinically, was actually a desmoplastic melanoma.