Gastrointestinal stromal tumor of the uterus: a case report with genetic analyses of c-kit and PDGFRA genes. Int J Gynecol Pathol. 2009;28:29-34. [PMID: 19047911 DOI: 10.1097/pgp.0b013e3181808000]

Follicular Dendritic Cell Sarcoma of Uterine Corpus: Report of 2 Cases

Follicular dendritic cell sarcoma is a rare dendritic/histiocytic tumor of intermediate malignant potential, which often involves extranodal sites, most commonly the gastrointestinal tract and mediastinum with only 5 cases reported in the female genital tract. We present the clinical and pathologic features of 2 such examples arising in the uterine corpus. Both patients (63 and 72-yr old) presented with postmenopausal bleeding and underwent an endometrial biopsy diagnostic of follicular dendritic cell sarcoma that was followed by hysterectomy. The tumors were polypoid, 3.5 and 5.0 cm, and were confined to the endometrium. Microscopically, ovoid to round to spindled tumor cells with pale eosinophilic cytoplasm and vesicular nuclei were arranged predominantly in sheets with an accompanying lymphocyte-rich inflammatory infiltrate. The tumor cells were positive for CD35, CD23, D2-40 in both tumors and additionally positive for CD21 in 1 tumor, all highlighting cell bodies and processes. Patients were alive without evidence of disease at 1 and 4 years with no adjuvant treatment. These cases highlight the importance of entertaining a broad differential diagnosis in lesions with epithelioid and/or spindled morphology involving the uterus.

Human ductal plate and its derivatives express antigens of cholangiocellular, hepatocellular, hepatic stellate/progenitor cell, stem cell, and neuroendocrine lineages, and proliferative antigens

Molecular mechanisms of human ductal plate (DP) development and differentiation (DD) are unclear. The author immunohistochemically investigated expressions of cholangiocellular antigens (CEA, CA19-9, EMA, MUC1, MUC2, MUC5AC, MUC6, mucins, CK7, and CK19), hepatocellular antigens (HepPar1, AFP, CK8, and CK18), hepatic stellate/progenitor cell (HSC) antigens or stem cell (SC) antigens (C-erbB2, CD56, chromogranin, synaptophysin, bcl2, NSE, NCAM, KIT, and PDGFRA), and proliferating antigen (Ki67) in 32 human fetal livers (HFL). The DD of human intrahepatic bile duct (IBD) could be categorized into four stages: DP, remodeling DP, remodeled DP, and immature IBD. All the molecules examined were expressed in the DP and DP derivatives. These results suggest that human DP or DP derivatives have capacities to differentiate into cholangiocellular, hepatocellular, HSC, SC, and neuroendocrine lineages. The data also suggest that NCAM, KIT/SC factor-signaling, NSE, HGF/MET signaling, PDGFa/PDGFRA signaling, chromogranin, synaptophysin, and CD56 play important roles in DD of DP and biliary cells of HFL. DP, DP derivatives, and IBD in HFL have proliferative capacity.

Coexisting and possible primary extra-gastrointestinal stromal tumors of the pancreas and liver: A single case report

Gastrointestinal stromal tumors (GIST) are mesenchymal neoplasms of the gastrointestinal tract (GI) that are defined, in part, by the expression of CD117, a c-Kit proto-oncogene protein. GISTs emerge outside of the GI at a very low frequency, typically in a single organ or location. GISTs that occasionally emerge outside of the GI are classified as extra-gastrointestinal stromal tumors (EGIST). The present study reports an extremely rare case of EGIST detected in the pancreas and the liver. The pancreatic and liver tumors were 4.5×2.5 cm and 2.0×1.5 cm in size, respectively. Both tumors consisted of CD117-positive spindle cells with a similar mitotic rate of 1–2 per 50 high power fields. The pancreatic and the hepatic EGISTs were at a low risk of malignancy, and both tumors were proposed to be primary stromal tumors. To the best of our knowledge, this is the first report of likely primary EGIST identified in the pancreas and liver of the same patient.

Primary extragastrointestinal stromal tumor of the pleura: A case report

Gastrointestinal stromal tumors (GISTs) are the most common type of mesenchymal tumor of the gastrointestinal tract. The stomach and small intestine are the most common sites of occurrence. GISTs are mesenchymal neoplasms originating from the interstitial cells of Cajal (ICCs), and are characterized by positivity for cluster of differentiation (CD) 117, also known as proto-oncogene c-Kit. While the majority of GISTs develop in the alimentary tract, in rare cases they may also be found in extragastrointestinal tissues. This type of GIST is known as an extragastrointestinal stromal tumor (EGIST). Despite the fact that EGISTs have been reported in the mesentery, omentum and retroperitoneum, primary intrathoracic EGISTs, arising from the pleura or lungs, are rare. The patient presented in the current study was a 40-year-old man, who presented with a cough and pyrexia, with pleural effusion on the left side. Multiple nodules throughout the parietal pleura were identified by thoracoscopy and a diagnosis of primary GIST of pleura was established, since they were positive for CD117 and discovered on GIST-1 and there was no evidence of gastrointestinal tumors. Subsequently, the patient was administered with imatinib and had no signs of disease recurrence 2 years later.

The potential role of telocytes in Tissue Engineering and Regenerative Medicine

Research and ideas for potential applications in the field of Tissue Engineering (TE) and Regenerative Medicine (RM) have been constantly increasing over recent years, basically driven by the fundamental human dream of repairing and regenerating lost tissue and organ functions. The basic idea of TE is to combine cells with putative stem cell properties with extracellular matrix components, growth factors and supporting matrices to achieve independently growing tissue. As a side effect, in the past years, more insights have been gained into cell-cell interaction and how to manipulate cell behavior. However, to date the ideal cell source has still to be found. Apart from commonly known various stem cell sources, telocytes (TC) have recently attracted increasing attention because they might play a potential role for TE and RM. It becomes increasingly evident that TC provide a regenerative potential and act in cellular communication through their network-forming telopodes. While TE in vitro experiments can be the first step, the key for elucidating their regenerative role will be the investigation of the interaction of TC with the surrounding tissue. For later clinical applications further steps have to include an upscaling process of vascularization of engineered tissue. Arteriovenous loop models to vascularize such constructs provide an ideal platform for preclinical testing of future therapeutic concepts in RM. The following review article should give an overview of what is known so far about the potential role of TC in TE and RM.

Immunohistochemistry of Telocytes in the Uterus and Fallopian Tubes

The seminal work of Popescu and colleagues first demonstrated the existence of a new cell type - the telocytes. We were among the first who reported the presence of such cells in the female genital tract and performed TEM examinations, as well as immunohistochemical staining in the attempt to find a specific marker. Telocytes from rat and from the human uterus and from human fallopian tube were extensively investigated initially by comparison with interstitial cells of Cajal. Progress in telocyte research led to the identification of different subtypes suggestive for a heterogeneous telocyte population which can even coexist in the same location. As a consequence, the functions of TCs are still elusive and can be considered a versatile phenomenon that depends on a variety of conditions, including signal reception and transmission of information via extracellular vesicles or by direct intercellular contact.

Primary gastrointestinal stromal tumor of the liver treated with sequential therapy

A 67-year-old female presented with a primary hepatic gastrointestinal stromal tumor that was detected by computed tomography and diagnosed based on histopathological and genetic analyses. The tumor was microscopically composed of spindle cells and epithelioid cells, and immunohistochemistry results showed positive staining for CD117 and CD34 expression. A genetic analysis revealed a heterozygous point mutation and deletion in exon 11 of c-KIT. After an R0 resection, imatinib mesylate was administered for 1 year until its use was discontinued due to severe side effects. Two years after the original operation, the tumor recurred in the residual liver and was completely resected again. Imatinib mesylate was administered for 2 years until it was replaced by sunitinib malate because of disease progression. The patient has survived for 53 mo after undergoing a sequential therapy consisting of surgical excision, imatinib and sunitinib.

Histopathological study using computer database of 10 000 consecutive gastric specimens: (1) benign conditions

Using a computer database, the author investigated the histopathology of 10 000 consecutive gastric specimens, taken in the last 12 years (2002–2013) at the pathology laboratory of a Japanese hospital. Re-observation of the already examined histological sections was done when the histological diagnosis and findings on the computer data base were not very obvious. The gastric specimens were identified as 8579 benign conditions and 1421 malignant lesions. The 8579 benign conditions were comprised almost normal stomach in 74 cases (0.9%), chronic gastritis in 4374 (51.0%), benign gastric peptic ulcer in 2195 (25.6%), foveolar hyperplastic polyp in 1004 (11.7%), fundic gland polyp in 421 (4.9%), adenoma in 487 (5.6%), heterotopic pancreas in 9 (0.1%), pancreatic acinar metaplasia (PAM) in 8 (0.1%), and amyloidosis in 7 (0.1%). Chronic gastritis showed lymphocytic infiltration and frequently showed erosions and intestinal metaplasia. Gastric peptic ulcer showed exudate, necrosis, active inflammation, and regenerative atypia of the epithelium. Foveolar hyperplastic polyp revealed 23 malignant changes and frequently showed dysplastic glands and intestinal metaplasia. Fundic gland polyp demonstrated cystic dilations of fundic gland ducts. Gastric adenoma showed adenomatous proliferation in the superficial mucosa and cystic dilation of the epithelium under the adenoma. Heterotopic pancreas was located in the submucosa and consisted of acinar cells, ducts, and occasionally islets. PAM was a tiny lesion in the mucosa and consisted of only pancreatic acinar cells. Amyloidosis was primary amyloidosis with positive reaction with Congo-red stain.

Histopathological study using computer database of 10 000 consecutive gastric specimens: (2) malignant lesions

Using a computer database, the author investigated the histopathology of 10 000 consecutive gastric specimens collected in the last 12 years 2002–2013 at his pathology laboratory in a relatively large hospital in Japan. Examination of histological sections was done when appropriate. The gastric specimens were made up of 8579 benign conditions and 1421 malignant lesions. The latter comprised gastric carcinoma in 1342 cases (94.4%), gastrointestinal stromal tumor (GIST) in 34 (2.4%), mucosal-associated lymphoid tissue (MALT) lymphoma in 25 (1.8%), non-Hodgkin's malignant lymphoma in 19 (1.3%), and metastatic carcinoma in 1 case (0.1%). Of the 1342 cases of gastric carcinoma, the histological type was as follows: tubular adenocarcinoma in 755 cases, papillary adenocarcinoma in 176, mucinous adenocarcinoma in 147, signet ring cell carcinoma in 145, poorly differentiated adenocarcinoma in 114, adenosquamous carcinoma in 4, and metastatic small cell carcinoma from the lung in 1. In surgically resected cases, the number of early gastric carcinomas was 258 and of advanced carcinoma, 521 cases. In GIST (n = 34), there were 2 cases of the epithelioid type and 32 of the spindle cell type. The size of GIST ranged from 1–15 cm, with a mean of 5.6 cm. KIT (CD117) was positive in 34/34 cases, CD34 in 31/34, desmin 2/34, and S100 4/34. A genetic analysis was performed in 6 cases of GIST, all of which showed point mutation of KIT and/or PDGFRA genes. In MALT lymphoma (n = 25), centrocyte-like cells and lymphoepithelial lesions were seen in every case. Helicobactor pylori infection was noted in 92%. In non-Hodgkin's lymphoma (n = 19), 17 cases were of diffuse large B-cell lymphoma, and 1 was peripheral T-cell lymphoma, while 1 was NK-cell lymphoma.

Telocytes revisited

Telocytes (TCs) are a novel interstitial (stromal) cell type described in many tissues and organs (www.telocytes.com). A TC is characterized by a small cell body (9–15 μm) and a variable number (one to five) of extremely long and thin telopodes (Tps), with alternating regions of podomers (∼80 nm) and podoms (250–300 nm). Tps are interconnected by homo- and heterocellular junctions and form three-dimensional networks. Moreover, Tps release three types of extracellular vesicles: exosomes, ectosomes, and multivesicular cargos, which are involved in paracrine signaling. Different techniques have been used to characterize TCs, from classical methods (light microscopy, electron microscopy) to modern ‘omics’. It is considered that electron microscopy is essential for their identification, and CD34/PDGFRα double immunohistochemistry can orientate the diagnosis. Functional evidence is accumulating that TCs may be intimately involved in the maintenance of tissue homeostasis and renewal by short- and long-distance intercellular communication. This review focuses on the most recent findings regarding TC features and locations and the principal hypotheses about their functions in normal and diseased organs. TC involvement in regenerative medicine is also considered.

Decidualization of uterine adenomyoma in a pregnant woman: a case report with immunohistochemical study

BACKGROUND

Decidualization of uterine adenomyoma has not been reported, to the best of the author's knowledge.

AIM

To report a case of uterine adenomyoma with decidualization.

CASE REPORT

A 43-year-old pregnant woman with "myoma" underwent cesarean operation and "myomectomy" at 37 gestation weeks. The operation was successful, and the baby and mother were healthy. Grossly, the "myoma" measured 12 × 10 × 10 cm, and the consistency was firm. Microscopically, the tumor was adenomyoma consisting of smooth muscle bundles and endometrial islands. Characteristically, the endometrial stroma showed marked decidualization. An immunohistochemical study showed that the decidual cells were positive for pancytokeratin AE1/3, pancytokeratin CAM5.2, cytokeratin (CK)7, CK18, vimentin, CA125, CD10, estrogen receptor (ER), progesterone receptor (PgR), and Ki-67 (labeling 1 %). They were negative for CK34βE12, CK5/6, CK8, CK14, CK19, CK20, EMA, p63, desmin, α-smooth muscle actin, S100 protein, CK34, CD68, and p53. These results show that marked decidualization occurs in adenomyoma during pregnancy, and that the decidual cells are positive for pancytokeratin AE1/3, pancytokeratin CAM5.2, CK7, CK18, vimentin, CA125, CD10, ER, and PgR.

CONCLUSION

A rare case of uterine adenomyoma with decidualization is reported.

Human fetal ductal plate revisited. I. ductal plate expresses NCAM, KIT, MET, PDGFRA, and neuroendocrine antigens (NSE, chromogranin, synaptophysin, and CD56)

BACKGROUND

The molecular mechanisms of ductal plate (DP) development and differentiation (DD) in human fetal livers (HFLs) are unclear.

MATERIALS AND METHODS

The author immunohistochemically investigated expressions of NCAM, KIT, KIT, PDGFRA, and neuroendocrine antigens in 32 HFLs.

RESULTS

The processes of human intrahepatic bile duct (IBD) DD could be categorized into four stages: DP, remodeling DP, remodeled DP, and mature IBD. NCAM was always expressed in DP and remodeling DP, but not in remodeled DP and mature IBD. The biliary elements were positive for cytokeratin (CK)7, 8, 18, and 19. The hepatoblasts were positive for CK8 and CD18, but negative for CK7 and CK19; however, periportal hepatoblasts showed biliary-type CKs (CK7 and CK19). NCAM was always expressed in DP and remodeling DP, but not in remodeled DP and mature IBD. KIT was occasionally (12/32 cases) expressed in DP and remodeling DP, but not in remodeled DP and mature IBD. NCAM expression was also seen in some hepatoblasts and hematopoietic cells and neurons. KIT was also expressed in some hepatoblasts, hematopoietic cells, and mast cells. MET and PDGFRA were strongly expressed in DP, remodeling DP, remodeled DP, and mature IBD. MET and PDGFRA were also strongly expressed in hepatoblasts and hematopoietic cells. MET and PDGFRA were not expressed in portal mesenchyme, portal veins, sinusoids, and hepatic veins. DP showed immunoreactive chromogranin, synaptophysin, neuron-specific enolase (NSE), and CD56. Expressions of chromogranin and CD56 were infrequently seen in remodeling DP. No expressions of these four neuroendocrine antigens were seen in remodeled DP and mature IBD. The nerve fibers were consistently positive for chromogranin, synaptophysin, NSE, and CD56 in the portal mesenchyme in the stages of remodeling DP, remodeled DP, and mature IBDs.

CONCLUSIONS

The data suggest that NCAM, KIT/stem cell factor-signaling, NSE, hepatocyte growth factor/MET signaling, PDGFα/PDGFRA signaling, chromogranin, synaptophysin, and CD56 play important roles in DD of biliary cells of HFL. They also suggest that the DP cells having neuroendocrine molecules give rise to hepatic stem/progenitor cells.

Imaging findings of primary malignant gastrointestinal stromal tumor of the liver

A primary gastrointestinal stromal tumor (GIST) arising in the liver is extremely rare. In our case of GIST, CT and MRI showed a well-defined, weakly enhancing mass with a cystic component in the left lateral segment of the liver that showed homogeneous and avid (18)F-fluorodeoxyglucose ((18)F-FDG) accumulation on positron emission tomography/computed tomography (PET/CT). We herein present a rare case of primary malignant GIST of the liver presenting with peritoneal seeding on CT, gadoxetic acid-enhanced MRI and (18)F-FDG PET/CT.

Primary gastrointestinal stromal tumor of the liver: report of a case

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. They can occur anywhere in the gastrointestinal tract, and rarely outside the digestive tract. We herein report a case of primary gastrointestinal stromal tumor that was resected from the liver of a 56-year-old male, which is the sixth description of a primary hepatic gastrointestinal stromal tumor. The tumor was shown to be completely limited within the liver by radiological, intraoperative and pathological examinations. The pathological results demonstrated an intermediate risk gastrointestinal stromal tumor, and immunohistochemical expression of CD117 was positive. Although rare, we suggested that GISTs should be considered in the differential diagnosis of hepatic nodules, and that not all hepatic gastrointestinal stromal tumors should automatically be considered to be metastases from a primary gastrointestinal site.

DOG1 immunoreactivity in uterine leiomyosarcomas

AIMS

DOG1 is a recently described marker of gastrointestinal stromal tumour (GIST) which is considered to be extremely sensitive and, among mesenchymal neoplasms, quite specific for this tumour type. Following the identification of DOG1 immunoreactivity in a uterine leiomyosarcoma, we wished to ascertain how prevalent DOG1 immunoreactivity was in this tumour type.

METHODS

We stained a series of uterine leiomyosarcomas (n=26) with DOG1 and with CD117 (c-kit), another marker of GIST. Staining with both markers was classified as negative, focal (<50% tumour cells positive) or diffuse (≥50% tumour cells positive).

RESULTS

DOG1 immunoreactivity was present in seven of 26 (27%) leiomyosarcomas. Staining was focal in five cases and diffuse in two. CD117 was positive in three of 26 (11.5%) cases, two focal and one diffuse. Two cases were positive with DOG1 and CD117. One of five uterine leiomyomas was focally positive with DOG1, and one extrauterine pelvic leiomyoma was diffusely positive with this marker.

CONCLUSIONS

Since GISTs have rarely been described as primary uterine neoplasms, the presence of DOG1 immunoreactivity in a uterine leiomyosarcoma may result in diagnostic confusion, and a panel of markers is necessary for diagnosis. Uterine leiomyosarcomas should be added to the list of mesenchymal neoplasms which may be DOG1 positive.

Projected focal nodular hyperplasia of the liver with pronounced atypical ductular reaction resembling ductal plate and expressing KIT

A 26-year-old woman was found to have a left abdominal tumor in the space among the hepatic left lobe, stomach and spleen. A laparoscopic examination revealed that the tumor was a projected liver tumor, and resection of the tumor was performed. Grossly, the tumor was not encapsulated and measured 4 cm × 4 cm × 5 cm. Microscopically, the tumor was composed of mature hepatocytes, fibrous septae, abnormal vessels and ductular reaction (DR). A pathological diagnosis of projected focal nodular hyperplasia (FNH) was made. Characteristically, the cells of the DR showed atypical features such as small cells and hyperchromatic nuclei. The DR assumed the features of ductal plate-like structures and immunohistochemically expressed KIT, suggesting that the cells of DR are stem cells and that when the stem cells proliferate they take a form of ductal plate-like structures, similar to fetal bile duct development. Immunohistochemically, the cells of DR were positive for cytokeratin (CK) AE1/3, CK CAM5.2, CK7, CK8, CK18, CK19, carcinoembryonic antigen (CEA), CA19-9, Ki-67 (labeling = 3%) and KIT, but negative for CK20, p53, TTF-1, CDX2, MUC1, MUC2, MUC5AC and MUC6. The hepatocytes were positive for CK CAM5.2, CK8, CK18 and Ki-67 (labeling = 4%), but negative for CK AE1/3, CK7, CK19, CK20, CEA, CA19-9, p53, KIT, TTF-1, CDX2, MUC1, MUC2, MUC5AC and MUC6. In conclusion, the author reported a projected FNH. The DR of the FNH showed atypical features such as small cells and hyperchromatic nuclei. The DR assumed features of ductal plate-like structures. KIT was positive in the DR in the FNH, suggesting that the cells of DR are liver stem cells, and proliferation of these cells take features of ductal plate-like structures, similar to embryonic biliary development. MUC apomucins are negative in the DR.

Gastrointestinal stromal tumors: a review of case reports, diagnosis, treatment, and future directions

Gastrointestinal stromal tumor (GIST) is a nonepithelial, mesenchymal tumor first described by Mazur and Clark in 1983. Since then, its molecular biology has been studied in great detail. Special interest in the role of tyrosine kinase in its regulation has been the target by different drug research. Mutation in c-kit exons 9, 11, 13, 17 and PDGFRA mutation in exons 12, 14, 18 are responsible for activation of gene signaling system resulting in uncontrolled phosphorylation and tissue growth. However, 5 to 15% of GISTs does not harbor these mutations, which raises additional questions in another alternate signaling pathway mutation yet to be discovered. Diagnosis of GISTs relies heavily on KIT/CD117 immunohistochemical staining, which can detect most GISTs except for a few 3% to 5% that harbors PDGFRA mutation. Newer staining against PKC theta and DOG-1 genes showed promising results but are not readily available. Clinical manifestation of GISTs is broad and highly dependent on tumor size. Surgery still remains the first-line treatment for GISTs. The advancement of molecular biology has revolutionized the availability of newer drugs, Imatinib and Sunitinib. Together with its advancement is the occurrence of Imatinib/Sunitinib drug resistance. With this, newer monoclonal antibody drugs are being developed and are undergoing clinical trials to hopefully improve survival in patients with GISTs.

Esophageal combined carcinomas: Immunohoistochemical and molecular genetic studies

Primary esophageal combined carcinoma is very rare. The authors herein report 2 cases. Case 1 was a combined squamous cell carcinoma and small cell carcinoma, and case 2 was a combined squamous cell carcinoma, adenocarcinoma, and small cell carcinoma. Case 1 was a 67-year-old man with complaints of dysphagia. Endoscopic examination revealed an ulcerated tumor in the middle esophagus, and 6 biopsies were obtained. All 6 biopsies revealed a mixture of squamous cell carcinoma and small cell carcinoma. Both elements were positive for cytokeratin, epithelial membrane antigen, and p53 protein, and had high Ki-67 labeling. The small cell carcinoma element was positive for synaptophysin, CD56, KIT, and platelet-derived growth factor-α (PDGFRA), while the squamous cell carcinoma element was not. Genetically, no mutations of KIT and PDGFRA were recognized. The patient died of systemic carcinomatosis 15 mo after presentation. Case 2 was a 74-year-old man presenting with dysplasia. Endoscopy revealed a polypoid tumor in the distal esophagus. Seven biopsies were taken, and 6 showed a mixture of squamous cell carcinoma, small cell carcinoma, and adenocarcinoma. The 3 elements were positive for cytokeratins, epithelial membrane antigen, and p53 protein, and had high Ki-67 labeling. The adenocarcinoma element was positive for mucins. The small cell carcinoma element was positive for CD56, synaptophysin, KIT, and PDGFRA, but the other elements were not. Mutations of KIT and PDGFRA were not recognized. The patient died of systemic carcinomatosis 7 mo after presentation. These combined carcinomas may arise from enterochromaffin cells or totipotential stem cell in the esophagus or transdifferentiation of one element to another. A review of the literature was performed.

Malignant melanoma of the conjunctiva: a case report with examination of KIT and PDGFRA

Although many clinicopathological studies of malignant melanoma of the conjunctiva have been reported, there have been no studies of the expression and gene mutations of KIT and PDGFRA in melanoma of the conjunctiva. A 69-year-old Japanese woman consulted our hospital because of black mass (0.7 × 0.7 × 0.6 cm) in the conjunctiva. A biopsy was taken. The biopsy showed malignant epithelioid cells with melanin deposition. Immunohistochemically, the tumor was positive for S100 protein, HMB45, p53, Ki-67 (labeling=30%), KIT and PDGFRA. The tumor was negative for pancytokeratins (AE1/3 and CAM5.2). A genetic analysis using PCR-direct sequencing revealed no mutations of KIT gene (exons 9, 11, 13, and 17) and PDGFRA gene (exons 12 and 18). The pathological diagnosis was conjunctival melanoma. Despite chemotherapy, the patient developed multiple metastases of melanoma, and died of melanoma 7 years after the biopsy. In conclusion, the author reported a case of melanoma of conjunctive expressing KIT and PDGFRA proteins without gene mutations of KIT and PDGFRA.

Malignant melanoma of the nasal cavity: a case report with examination of KIT and platelet derived growth factor receptor-α(PDGFRA)

Although several clinicopathological studies of malignant melanoma of the nasal cavity have been reported, there are no studies of the expression and gene mutation of KIT and platelet derived growth factor receptor-α (PDGFRA) in melanoma of the nasal cavity. A 92-year-old Japanese woman consulted to our hospital because of right nasal obstruction and epistaxis. Physical examination and imaging modalities showed a tumor of the right nasal cavity. A biopsy was taken, and it showed malignant epithelioid cells with melanin deposition. Immunohistochemically, the tumor was positive for S100 protein, HMB45, p53, Ki-67 (labeling=20%), KIT and PDGFRA. The tumor was negative for cytokeratins (AE1/3 and CAM5.2). A genetic analysis using PCR-direct sequencing revealed no mutation of KIT gene (exons 9, 11, 13, and 17) or the PDGFRA gene (exons 12 and 18). The pathological diagnosis was primary malignant melanoma of the nasal cavity. The tumor was reduced in size by local resection and chemotherapy (Darthmose regimen: dacarbazine, carmustine, cisplatine, and tamoxifen), and the patient is now alive and free from metastasis 9 months after the first manifestation. In conclusion, the author reported a case of melanoma of the nasal cavity expressing KIT and PDGFRA without gene mutations of KIT and PDGFRA.

Application of ultrasonography in the diagnosis and treatment of gastric stromal tumors

Gastric stromal tumors are common mesenchymal tumors of the gastrointestinal tract. Common clinical manifestations include abdominal pain, bowel obstruction, gastrointestinal bleeding, and abdominal mass. Gastric stromal tumors show a histological feature of spontaneous differentiation. Ultrasound examination plays an important role in the diagnosis and treatment of gastric stromal tumors. Here we review the application of ultrasonography in the diagnosis and treatment of gastric stromal tumors.

Sinonasal-type hemangiopericytoma of the nasal cavity and paranasal sinus

Sinonasal-type hemangiopericytoma is a very rare disease. A 64-year-old man was admitted to our hospital because of nasal obstruction. Nasal endoscopy showed a polyp in the right nasal cavity. Imaging modalities including CT and MRI revealed polypoid tumors in the right nasal cavity and right sphenoid sinus. Excision of the tumors was performed. Macroscopically, the nasal tumor was reddish and focally cystic, and the tumor of the sphenoid sinus was reddish and solid. Microscopically, round and polygonal cells were seen to proliferate monotonously in a medullary fashion. Each tumor cell had a vesicular nucleus and amphophilic cytoplasm. The cellularity was high and mitotic figures were recognized in 6 per 10 high-power fields. Many thin-walled vessels were embedded within the tumor. No collagenization was recognized. A silver stain showed that fine argyrophilic fibers encased individual cells and a few cell nests. Mild invasion into the surrounding tissue was recognized in focal areas. The tumor showed focal cystic and hemorrhagic changes. Immunohistochemically, the tumor cells were positive for vimentin, bcl-2 and factor XIIIa, and negative for cytokeratins, epithelial membrane antigen, CD34, desmin, α-smooth muscle antigen, myoglobin, myogenin, CD31, KIT, p53 protein, CD99, and factor VIII-related antigen. Ki-67 labeling was 17%. The pathological diagnosis was low-grade malignant sinonasal-type hemangiopericytoma. The patient was followed up, but no recurrence has been seen 4 years after the operation.

Heterotopic Pancreatic Tissue of the Stomach: Report of Three Cases and Consideration of Its Histogenesis

Heterotopic pancreatic tissue of the stomach is a rare condition. The author herein reports three cases of heterotopic pancreatic of the stomach. The three cases were found in the 8,154 gastric specimens (biopsy 6,122 cases, gastrectomy 2,032 cases) of our pathology laboratory; the frequency was 0.04%. The first case was a 57-year-old woman who presented with epigastralgia. Endoscopic examination revealed a submucosal tumor in the body of the stomach. Partial gastrectomy was performed. Histologically, the lesion measured 25 × 20 × 25 mm and was submucosal heterotopic pancreatic tissue with hemorrhage and cystic changes. It was composed of acinar cells, ducts, and islets (Heinrich type I). The second case was a 57-year-old man without symptoms. Endoscopic examination revealed a submucosal tumor, and biopsy was taken. The biopsy showed heterotopic pancreatic tissue in the mucosa. It consisted of acinar cells and ducts (Heinrich type II). The third case was a 54-year-old woman without symptoms. Endoscopic examination showed chronic gastritis, and biopsy was obtained. The biopsy revealed heterotopic pancreatic tissue in the mucosa. It consisted of acinar cells and ducts (Heinrich type II). The first case appears to be a true heterotopic pancreas of congenital abnormality. The second and third cases seem to be heterotopic pancreatic tissues of congenital anomaly of the gastric mucosa. The histogenesis of heterotopic pancreatic tissue is discussed.

Spindle Cell Carcinoma of the Common Bile Duct: Case Report with Immunohistochemical Analysis

The author reports a very rare case of spindle cell carcinoma of the common bile duct with an emphasis on immunohistochemical features. A 65-year-old man was admitted to our hospital because of jaundice. Imaging modalities revealed a tumor of the common bile duct, and bile cytology demonstrated malignant cells. A pancreatico-duodenectomy was performed. Grossly, an elevated tumor (15 × 10 × 3 mm) was present in the middle portion of the common bile duct. Microscopically, the tumor consisted of well-differentiated adenocarcinoma (20% in area) and spindle cell carcinoma (80% in area). There were gradual transitions between the two. The tumor cells invaded into the serosa. Immunohistochemically, the spindle cell carcinoma element was positive for four types of pancytokeratins, cytokeratin 7 (CK7), CK8, CK18, CK19, CK20, epithelial membrane antigen, vimentin, p53 protein, Ki-67 (labeling = 52%), and CEA. It was negative for high-molecular-weight CK, CK5/6, CK14, p63, neuron-specific enolase chromogranin, synaptophysin, CD56, CA19-9, CD34, desmin, S100 protein, myoglobin, a-smooth muscle antigen, CD34, CD68 and KIT. The adenocarcinoma element showed similar immunoreactivity except for negative vimentin, and positive CA19-9. The present case is the first report of spindle cell carcinoma of the common bile duct demonstrating an extensive immunohistochemistry. The spindle cell carcinoma in the present case may be derived from sarcomatous transformation of the adenocarcinoma element. CK20 newly emerges in the development of spindle cell carcinoma of the common bile duct.

Spindle cell carcinoma of the nasal cavity

We report an extremely rare case of spindle cell carcinoma of the sinonasal cavity. A 75-year-old man was admitted to our hospital because of right nasal obstruction. Nasal endoscopy showed a polypoid tumor measuring 3 × 3 cm at the nasal septum in the right nasal cavity, and an excisional biopsy was performed. Computed tomography (CT) demonstrated the nasal tumor extended to the maxillary sinus. Histologically, the tumor consisted of malignant spindle cells with hyperchromatic nuclei. Mitotic figures and necrosis were recognized. In some areas, edematous changes were recognized. No apparent differentiation was noted. The tumor cells were free of keratinization and intercellular bridge formations; therefore, there were no squamous cell components. Immunohistochemically, the tumor cells were positive for pancytokeratin, cytokeratin (CK)5/6, CK18, CK19, high molecular weight CK, p63, and vimentin. The tumor cells were negative for epithelial membrane antigen, CK7, CK14, p53 protein, S100 protein, HMB45, chromogranin, synaptophysin, CD34, CD56, glial fibrillary acidic protein, neuron-specific enolase, neurofilaments, α-smooth muscle actin, neuroblastoma, myoglobin, carcinoembryonic antigen (CEA), carbohydrate antigen (CA)19-9, CD3, CD20, CD30, CD45RO, and CD45. A pathological diagnosis of spindle cell carcinoma of sinonasal lesion was made. The patient underwent resection of right maxilla followed by chemotherapy and radiation and was alive without metastasis 5 years after initial presentation.

Monolobar hepatobiliary fibropolycystic disease

We herein report a case of monolobar hepatobiliary fibropolycystic disease. A 75-year-old woman presented with heartburn. Imaging modalities including US, CT, and MRI revealed marked atrophy and multiple biliary cysts of the hepatic left lobe. The hepatic right lobe was normal. ERCP and bile duct endoscopy revealed anomalous pancreaticobiliary union, choledochal dilation, dilation of left intrahepatic bile ducts, and small choledochal non-invasive adenocarcinoma. Polycystic kidney diseases were absent. The patient underwent pancreatico-duodenectomy and extended hepatic left lobectomy. Grossly, the hepatic left lobe was markedly atrophic, and studded with numerous biliary cysts. The left intrahepatic bile ducts were dilated (Caroli's disease) and the common bile duct showed type I choledochal dilation. The right hepatic lobe was normal. Histologically, the hepatic left lobe was replaced by fibroelastosis. The intrahepatic bile ducts showed ductal plate malformation such as irregular contours, invaginations, and protrusions. The numerous biliary cysts also showed ductal plate malformation. There were numerous persistent ductal plates and microhamartomas. Many hyalinized destructive biliary cysts and ductal plates were recognized. The liver parenchyma was scant and free of hepatocellular malformations. The portal veins showed old obliterative portal thrombosis. The right hepatic lobe was normal. Immunohistochemically, the biliary cells were positive for cytokeratin 7, 8, 18 and 19, and MUC6 and CD10, but negative for MUC2 and MUC5AC. The biliary cysts, persistent ductal plate, and microhamartomas were positive for fetal apomucin antigen MUC1.

Low incidence of KIT gene mutations and no PDGFRA gene mutations in primary cutaneous melanoma: an immunohistochemical and molecular genetic study of Japanese cases

BACKGROUND

Although several studies have reported the incidence of KIT and PDGFRA gene mutations in cutaneous melanomas of Caucasians, only one report is available for Mongoloids, including Japanese. In Japan, melanoma is an uncommon neoplasm compared with countries with Caucasian populations.

METHODS

In this study, protein expression and gene mutations of these two genes were investigated by immunohistochemistry and PCR-direct sequencing in 12 primary cutaneous invasive melanomas of Japanese patients. Acral melanoma was detected in 2 cases, chronically sun-damaged skin melanoma in 3 cases, and non-chronically sun-damaged skin melanoma in 7 cases. Genetic analysis was performed in exons 9, 11, 13, and 17 of the KIT gene and in exons 12 and 18 of the PDGFRA gene.

RESULTS

Point mutations of the KIT gene were recognized in only one (8%) case, codon 559 of exon 11 (GTT → GCT). This is a melanoma of the sole (acral melanoma). No mutations of the PDGFRA gene were recognized. At the protein level, 11 case (92%) showed membranous expression of KIT; the expression did not correlate with melanoma depth. KIT expression was stronger in the peripheral in situ or minimal invasive areas than the central invasive areas. Membranous PDGFRA expression was found in all cases (100%).

CONCLUSION

In this study, only 8% of melanomas had the KIT mutation in this Japanese population. The finding of a mutation in one of two acral melanomas suggests that KIT inhibitors, for example imatinib, which are already used in clinics for treatment of GIST, can also be used for melanoma.

Minute myopericytoma of the neck: a case report with literature review and differential diagnosis

Reports of cutaneous myopericytoma (MPC) are very rare. The author herein reports a case of minute MPC of the neck. A 56-year-old woman noticed a painful small tumor in the neck, and consulted to our hospital. Dermatologists's diagnosis is a hyperplastic lymph node. Excision of the tumor was performed. Grossly, the tumor was a sold white tumor measuring 3 × 3 × 3 mm. Microscopically, it consisted of many vascular channels and perivascular cell proliferation encased by a fibrous capsule. The vascular proliferation showed a hemangiopericytoma (HPC)-like pattern such as staghorn-like vessels. Fibrosis was not present. The HPC-like cells had vesicular nuclei and polygonal cytoplasm. No atypia is recognized. The HPC-like cells focally showed vague nodular proliferation around the vessels. Immunohistocheically, the tumor cells were negative for cytokeratin, and positive for vimentin. The vasculatures were positive for factor VIII-related antigen, CD34, and CD31. The HPC-like tumor cells were positive for α-smooth muscle actin and h-caldesmon, but negative for desmin, S100 protein, melanosome, bcl-2, CD99, and KIT. The Ki-67 labeling was 8% and p53 was negative. The pathologic diagnosis was MPC of the neck skin. The patient is now alive without recurrence 4 years after the excision. A review of the literature revealed 73 cases of MPC from 6 papers. MPC is male predominance, and the patients ages ranges from 13 to 87 years with the median of 47 years. The most common location was lower extremities followed in order by upper extremities, head and neck, and trunk. One MPC occurred within the vasculature, and 3 cases of MPC developed in the scar or trauma lesions. The prognosis after excision is good, but a very minority showed local recurrence. A differential diagnosis was also made.

Large cell neuroendocrine carcinoma with sarcomatous changes of the endometrium: a case report with immunohistochemical studies and molecular genetic study of KIT and PDGFRA

The author herein reports a very rare case of large cell neuroendocrine carcinoma (LCNEC) with sarcomatous changes of the endometrium. A 40-year-old woman was admitted to our hospital because of abnormal uterine bleeding. Gynecologic examination and imaging modalities revealed a polypoid tumor of the uterine corpus. Uterine curettage biopsy revealed a sarcomatous undifferentiated carcinoma. Simple hysterectomy, salpingo-oophorectomy, extensive lymph node dissection, and omentectomy were performed. The patient was diagnosed as having FIGO stage Ib (T1N0M0) carcinoma, and adjuvant chemotherapy was performed. The patient is now alive 16 months after the operation. Pathologically, a polypoid tumor measuring 3x2x2 cm(3) was found in the uterine corpus. Histologically, the tumor consisted of relatively large-sized carcinoma cells without differentiation. The tumor cells have abundant cytoplasm and prominent nucleoli. It was composed of a spindle cell component (40%) and an epithelioid component (60%). A gradual transition between the two was recognized. Immunohistochemically, both elements showed the same immunophenotypes. The carcinoma cells were positive for cytokeratin, vimentin, CA125, CD34, estrogen receptor, progesterone receptor, p53 protein, Ki-67 antigen (80%), synaptophysin, CD56, KIT, and PDGFRA. They were negative for epithelial membrane antigen, CEA, desmin, S100 protein, melanosome, alpha-smooth muscle actin, chromogranin, and neuron-specific enolase. A molecular genetic analysis revealed no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The final diagnosis was LCNEC with sarcomatous changes.

Primary gastrointestinal stromal tumor of the liver with PDGFRA gene mutation

Gastrointestinal stromal tumor is a mesenchymal tumor with KIT or PDGFRA gene mutation, occurring primarily in the stomach and intestine and rarely outside the digestive tract. KIT-negative tumors with epithelioid cell morphology and PDGFRA mutation represent a minor subset of gastrointestinal stromal tumor. Here, we describe a case of gastrointestinal stromal tumor in the liver of a 70-year-old man. The tumor was shown to be completely limited within the liver by radiologic, intraoperative, and pathologic examinations. Histopathologically, the tumor showed epithelioid cell-type morphology and immunohistochemical expression of CD34 and protein kinase C theta but was negative for cytokeratin, EMA, S-100, and HMB-45. KIT protein expression was very faint, and we judged it as negative. Mutation analysis revealed the presence of PDGFRA gene mutation (V561D) at exon 12. These findings are essentially the same as those typically seen in ordinary KIT-negative epithelioid cell-type gastrointestinal stromal tumor of the digestive tract. Although KIT-negative gastrointestinal stromal tumor occurring outside the gastrointestinal tract is very rare, this entity should be considered as a potential primary hepatic neoplasm.

Advances in pathological diagnosis of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. The pathogenesis of GIST may be associated with the mutations of oncogenic c-kit or platelet-derived growth factor receptor alpha (PDGFRA). The pathological diagnosis of GIST needs a combined approach of macropathology, histopathology, immunohistochemistry and gene testing. Preoperative diagnosis is very important for patients with GIST, especially for those needing individualized treatment. In this article, we will review the recent advances in pathological diagnosis of GIST and the consensus criteria for risk stratification of GIST. Besides, we will also summarize the molecular biological parameters used for evaluation of the biological behavior of GIST.

Cellular Fibromatous Neoplasms of the Ovary

Many ovarian tumors composed primarily of fibroblastic cells are fibromas of usual type, and generally do not pose diagnostic difficulty. These tumors can be diagnosed accurately in most instances based on morphology without needing immunohistochemistry. Approximately 10% of fibromatous neoplasms, however, exhibit increased cellularity and mitotic activity, and, in the presence of the former or both features, are classified as cellular fibroma or mitotically active cellular fibroma. Distinguishing these entities from fibrosarcoma, an exceptionally uncommon ovarian malignancy, is important. This article reviews fibromatous ovarian tumors, emphasizing cellular fibromas and their differential diagnosis.

Smooth Muscle Tumors of the Female Genital Tract

Smooth muscle tumors are the most common among mesenchymal tumors in the female genital tract. The vast majority of these neoplasms are clinically benign and easy to diagnose. In contrast, leiomyosarcomas are highly aggressive tumors that may pose considerable diagnostic problems when they display unusual (myxoid or epithelioid) morphology, ambiguous histologic features for malignancy, or an unusual anatomic distribution. Diagnostic criteria for these problematic tumors vary depending on the site and type of histologic differentiation, and are based on a combination of 3 major criteria: (1) moderate to severe cytologic atypia; (2) increased mitotic index; and (3) tumor cell necrosis. Certain benign smooth muscle proliferations may show worrisome histologic features or unusual growth patterns, causing concern for leiomyosarcoma. Furthermore, other tumors, including perivascular epithelioid tumors, may mimic leiomyosarcoma. Careful attention to the clinical and anatomic setting, cytologic and architectural features, and immunohistochemical characteristics are helpful in distinguishing these entities. This article discusses conventional smooth muscle tumors as well as unusual subtypes, with emphasis on the diagnostic criteria and problems in differential diagnosis that arise at each site within the female genital tract.

Immunohistochemical Markers of Value in the Diagnosis of Mesenchymal Lesions of the Female Genital Tract

Pure mesenchymal tumors may occur anywhere in the female genital tract, but they are most common in the uterine corpus, leiomyoma being by far the most prevalent. These tumors, and other uncommon mesenchymal lesions within the uterine corpus and elsewhere in the female genital tract, may result in several diagnostic problems. Morphology remains paramount and, in most cases, an unequivocal diagnosis can be made based on examination of the hematoxylin and eosin stained sections, combined with an appreciation of the clinical and gross pathologic features. In difficult cases, immunohistochemistry can significantly contribute to the final diagnosis. In this article, the immunohistochemistry of neoplastic and nonneoplastic mesenchymal lesions of the female genital tract is discussed site by site, concentrating on markers that are of value in diagnosis and in differential diagnosis. The immunophenotype of mixed epithelial and mesenchymal neoplasms and pure epithelial neoplasms with a component of spindle cells is discussed, where appropriate, because these can enter into the differential diagnosis of a pure mesenchymal lesion.

Primary small cell carcinoma of the pleura: a case report with immunohistochemical and molecular genetic analyses of KIT and PDGFRA genes

An extremely rare case of primary small cell carcinoma of the pleura with an emphasis on KIT and platelet-derived growth factor receptor-α (PDGFRA) genes is reported here. A 67-year-old man underwent left testicular orchiectomy because of a testicular tumor. The tumor was immunohistochemically shown to be diffuse large B-cell lymphoma. The patient was treated with chemotherapy and radiation and followed up in our hospital. Eight years after the orchiectomy, the patient (75 years old) developed left pleural tumor and pleural effusion, and a biopsy was performed. The biopsy revealed a medullary malignant tumor consisting of small round and spindle cells. The following three possibilities were considered: recurrent lymphoma, mesothelioma, and small cell carcinoma. Immunohistochemically, the tumor cells were positive for cytokeratin, synaptophysin, CD56, KIT, and PDGFRA, but negative for CEA, cytokeratin 5/6, neuron-specific enolase, chromogranin, CD45, CD3, CD20, CD45RO, CD15, CD30, calretinin, WT-1, B72.3, D2-40, and TTF-1. Therefore, a diagnosis of pleural small cell carcinoma was made. A molecular genetic analysis using PCR-direct sequencing identified no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The patient was treated with chemotherapy (cisplatin) and radiation (50 Gray). The present case is the first reported case of primary small cell carcinoma of the pleura with an examination of KIT and PDGFRA expressions and KIT and PDGFRA gene mutations.

Adenosquamous carcinoma in a congenital choledochal cyst associated with pancreatico-biliary maljunction

Congenital choledochal cyst is occasionally complicated by carcinomatous transformation, mostly adenocarcinoma. Adenosquamous carcinoma arising in a congenital choledochal cyst is very rare. The author herein reports an adenosquamous carcinoma arising in congenital choledochal cyst associated with pancreatico-biliary maljunction. A 34-year-old man with congenital choledochal cyst and recurrent cholangitis had been followed up, and was admitted to hospital to undergo testing for cancer. Imaging modalities including computed tomography, magnetic resonance imaging and endoscopic retrograde cholangiography showed an elevated lesion in the choledochal cyst. Because clinical cytology of bile indicated malignant cells, pancreatico-duodenectomy, cholecystectomy, and resection of the choledochal cyst were performed. Grossly, the choledochal cyst was type I, and its size was 8 x 10 cm. Anomalous pancreatico-biliary ductal union was recognized. An elevated lesion was recognized in the choledochal cyst. Histologically, the lesion was composed of a squamous cell carcinoma element and an adenocarcinoma element; a gradual transition was recognized between the two. The squamous cell carcinoma element contained microcytic cells with mucins. On immunohistochemistry the adenocarcinoma element and microcytic cells were positive for CEA, but the squamous cell carcinoma element was negative for CEA. Both elements were positive for CA19-9. Ki-67 labeling was 53% in the adenocarcinoma element and 48% in the squamous cell carcinoma element. p53 protein was negative in both elements. At the time of writing, the patient was alive after 25 months without recurrence or metastasis. The present case is the second case of adenosquamous carcinoma arising in congenital choledochal cyst in the English-language literature.

Pulmonary alveolar microlithiasis with cor pulmonale: an autopsy case demonstrating a marked decrease in pulmonary vascular beds

Pulmonary alveolar microlithiasis (PAM) is a very rare autosomal recessive disorder in which microliths are formed in the alveolar space. PAM is infrequently complicated by pulmonary hypertension, the cause of which is unclear. The author in this paper found that the pulmonary hypertension was caused by a marked decrease in pulmonary vascular beds. Here, an autopsy case of PAM with a marked cor pulmonale is reported. A 14-year-old woman was found to have an abnormal pulmonary shadow, but the cause was unclear. At 24 years, she was diagnosed with a diffuse pulmonary abnormal shadow. At 42 years, she was diagnosed with PAM by imaging techniques. Her condition gradually worsened and she had to be treated with oxygen. She died of respiratory failure at 54 years. An autopsy revealed severe PAM and marked cor pulmonale. The heart weighed 360 g and right ventricular thickness was 10 mm (normal, 2-3 mm). Microscopically, the alveolar space was diffusely filled with microliths, and heart failure cells were recognized. Bone formations were scattered. The alveolar walls showed fibrous thickening, and pulmonary arteries showed atherosclerosis. The right ventricle showed marked cardiac hypertrophy. Chronic severe liver congestion was noted. A morphometric analysis using CD34-stained specimens showed a marked decrease (one tenth) in pulmonary capillary beds (capillary number: 8.6 +/- 3.1 per image), compared with normal lungs obtained from two other autopsies (85.3 +/- 9.4 and 96.2 +/- 10,3). It was concluded that the cor pulmonale and pulmonary hypertension in the present case were caused by the marked decrease of the pulmonary arterial vascular beds. More research is required regarding the etiology and treatment of PAM.

Amelanotic malignant melanoma of the esophagus: Report of two cases with immunohistochemical and molecular genetic study of KIT and PDGFRA

The author reports herein two cases of amelanotic malignant melanoma of the esophagus. Case 1 is an 87-year-old woman who was admitted to our hospital because of nausea and vomiting. Endoscopic examination revealed an ulcerated tumor of the distal esophagus, and a biopsy was taken. The biopsy showed malignant polygonal and spindle cells. No melanin pigment was recognized. Immunohistochemically, the tumor cells were positive for melanosome (HMB45), S100 protein, KIT and Platelet derived growth factor receptor-α (PDGFRA). The patient was treated by chemotherapy and radiation, but died of systemic metastasis 12 mo after the presentation. Case 2 is a 56-year-old man presenting with dysphagia. Endoscopic examination revealed a polypoid tumor in the middle esophagus, and a biopsy was obtained. The biopsy showed malignant spindle cells without melanin pigment. Immunohistochemically, the tumor cells were positively labeled for melanosome, S100 protein, KIT and PDGFRA. The patient refused operation, and was treated by palliative chemotherapy and radiation. He died of metastasis 7 mo after the admission. In both cases, molecular genetic analyses of KIT gene (exons 9, 11, 13 and 17) and PDGFRA gene (exons 12 and 18) were performed by the PCR direct sequencing method, which showed no mutations of KIT and PDGFRA genes. This is the first report of esophageal malignant melanoma with an examination of the expression of KIT and PDGFRA and the mutational status of KIT and PDGFRA genes.