Cytomorphological features of sebaceous carcinoma of the breast.

Sebaceous carcinoma of the breast is an extremely rare histological subtype of breast cancer, with fewer than 30 cases reported to date. Because of its extremely rare histological presentation, there are few case reports that highlight its cytological findings. In this case report, the cytomorphological features of a sebaceous carcinoma of the breast are described in detail. Cytomorphological analysis revealed atypical cells presenting predominantly as loose clusters. No tubular or papillary structures were evident in the clusters and no mucin production was observed. The diagnosis of sebaceous carcinoma of the breast requires prominent sebaceous differentiation of cells. In Papanicolaou-stained smears, the differentiated tumor cells were found within the yellowish clusters. When these yellowish clusters were observed at high magnification and shifted out of focus, the sebaceous differentiation of tumor cells could be recognized. This finding is an advantage of observing Papanicolaou-stained specimens. Like previous reports, some individual cells showing sebaceous differentiation were also observed. In cases where many yellowish clusters appear, close observation of the interior of the clusters can confirm the presence of sebaceous differentiation of tumor cells and serve as a diagnostic clue for the cytological diagnosis of sebaceous carcinoma of the breast.

Predominance of T-bet-positive Th1 cells in infiltrating T-lymphocytes in most of active arteritis lesions of giant cell arteritis.

Immunological mechanisms through the activation of CD4-positive T-cells have been assumed to be involved in the pathogenesis of giant cell arteritis (GCA). Many studies employing frozen tissues of temporal artery biopsy, peripheral blood lymphocytes, and plasma of GCA patients have revealed the contribution of interferon-γ and interleukin-17 in both protein and mRNA levels. However, the analyses using formalin-fixed and paraffin-embedded (FFPE) tissue specimens, in which the correlation between histopathologic pictures and immunological circumstances would be elucidated, have been limited. Here, we performed the immunohistochemical analyses of infiltrating small lymphocytes in GCA lesions using FFPE specimens, especially of the subsets of CD4-positive T-cells by immunohistochemistry with antibodies against T-bet, GATA-3, RORγT, and Foxp3, which is the differentiation-specific transcription factor for Th1, Th2, Th17, and Treg cells, respectively. In these slides, the nuclear-positive staining is much more clearly and easily identifiable than the cytoplasmic staining for cytokines. The results indicate the predominance of T-bet-positive Th1 cells in infiltrating T-cells in most of active arteritis lesions of GCA. Furthermore, our data suggest the possible immunosuppressive microenvironment induced by T-reg cells and M2-type macrophages in the arteritis lesions throughout the course of GCA inflammation.

Jejunal gastrointestinal stromal tumor that developed in a patient with neurofibromatosis type 1: a case report.

BACKGROUND: Neurofibromatosis type 1 (NF1) is known to be associated with the frequent occurrence of unique gastrointestinal stromal tumors (GISTs), preferably occurring in the small intestine, with no mutations in the c-kit proto-oncogene or platelet-derived growth factor receptor-alpha (PDGFRA), with a high tendency for multifocal development, indolent nature, with low proliferation activity and favorable prognosis. CASE PRESENTATION: A woman in her forties visited her local doctor complaining of menstrual pain; a large mass was detected in her lower abdomen, and she was referred to our hospital. The patient had hundreds of skin warts and café au lait spots. The patient's mother had been diagnosed with type 1 neurofibromatosis. The patient met the diagnostic criteria for NF1 and was diagnosed with NF1. Ultrasonography showed a large heterogeneous cystic mass with various echo patterns, solid compartments and multiple septations. Magnetic resonance imaging showed a multilocular cystic mass with liquid content exhibiting various intensities, including that of blood. A small round solid mass was also observed close to the cystic tumor. Contrast-enhanced computed tomography showed that the round solid mass showed strong enhancement in the early phase, unlike the cystic tumor component. Open laparotomy revealed a multicystic exophytic tumor measuring 11.5 cm originating from the jejunal wall, 20 cm distal to the duodenojejunal flexure. A solid tumor measuring 2.1 cm was also found on the anal side of the large tumor. We resected the short segment of the jejunum, including the two lesions. Microscopic findings revealed that the cystic and solid tumors consisted of spindle-shaped tumor cells showing little atypia with a fascicular or bundle arrangement. Nuclear mitosis was scarce. Immunostaining of the tumor cells showed positive staining for KIT and DOG1 and negative staining for S100 and desmin. The NF1 patient was diagnosed with multiple GISTs accompanied by intratumoral hemorrhagic denaturation arising from the jejunum. The TNM staging was pT4N0M0, stage IIIA. CONCLUSION: We report a case of GISTs associated with NF1 that showed a jejunal origin, multifocal development and few mitotic figures. The recurrence risk, survival prognosis and need for adjuvant chemotherapy, particularly in cases where the initial GIST exhibits a very indolent pathology in NF1-related GISTs, remain to be elucidated.

Tiny Hydatidiform Mole Presenting As Pregnancy of Unknown Location.

Pregnancy of unknown location (PUL) is a condition in which a pregnancy test, such as elevation of serum or urine ß-human chorionic gonadotrophin (hCG) level, is rendered positive; however, intrauterine or extrauterine pregnancy cannot be confirmed by transvaginal sonography (TVS). Diagnostic dilation and curettage (D&C) or laparoscopy may be performed to search for the pregnancy location. We experienced a case of PUL in which D&C was performed and histological examination revealed a tiny complete hydatidiform mole within the uterine contents. A retrospective review of the clinical course of this case, such as the evaluation of serum ß-hCG levels and TVS findings, suggested that this medical entity could be explained by a tiny hydatidiform mole. In PUL, during D&C, when abnormal villi are detected, even if the lesion is tiny, a suspicion of a hydatidiform mole should be considered by the pathologists, and immunostaining and/or chromosome testing/molecular genotyping should be subsequently performed. Whether a tiny hydatidiform mole poses a risk of persistent gestational trophoblastic disease requires further study based on the accumulation of cases. D&C for PUL patients may be a useful procedure to determine such diagnoses and pick up cases.

Histological transformation to signet-ring cell carcinoma in a patient with clinically aggressive poorly differentiated adenocarcinoma of the ascending colon after response to chemotherapy plus cetuximab: a case report.

BACKGROUND: Alteration of chemosensitivity or tumor aggressiveness in response to chemotherapy has been reported, and liquid biopsy assessment during chemotherapy for colorectal cancers has confirmed the acquisition of mutations in various oncogenes. However, the occurrence of histological transformation seems to be extremely rare in colorectal cancers, and the few existing case reports of this transformation are from lung cancer and breast cancer. In this report, we describe the histological transformation of clinically aggressive scirrhous-type poorly differentiated adenocarcinoma of the ascending colon to signet-ring cell carcinoma in almost all recurrent tumors that were confirmed by autopsy after response to chemotherapy plus cetuximab. CASE PRESENTATION: A 59-year-old woman visited our hospital with whole abdominal pain and body weight loss and was diagnosed with scirrhous-type poorly differentiated adenocarcinoma of the ascending colon with aggressive lymph node metastases. The intrinsic chemosensitivity of the tumors was evident upon initiation of mFOLFOX6 plus cetuximab therapy, and right hemicolectomy was performed, and the tumor obviously remained in the peripancreatic area, paraaortic region, or other retroperitoneal areas. The ascending colon tumors mainly consisted of poorly differentiated adenocarcinoma and were not associated with signet-ring cell components except for minute clusters in a few lymphatic emboli in the main tumor. Chemotherapy was continued, and metastases were eliminated at 8 months after the operation; this response was maintained for an additional 4 months. Discontinuation of chemotherapy plus cetuximab resulted in immediate tumor recurrence and rapid expansion, and the patient died of the recurrent tumor 1 year and 2 months after the operation. Autopsy specimens revealed that almost all of the recurrent tumors exhibited transformation and consisted of signet-ring cell histology. CONCLUSION: This case might suggest that various oncogene mutations or epigenetic changes resulting from chemotherapy, especially regimens that include cetuximab, contribute to the transformation of non-signet-ring cell colorectal carcinoma to signet-ring cell carcinoma histology and can promote the aggressive clinical progression characteristic of signet-ring cell carcinoma.

Histologic and Immunohistochemical Evaluation of Infiltrating Inflammatory Cells in Kawasaki Disease Arteritis Lesions.

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology which predominantly affects medium- and small-sized muscular arteries. Histopathologic studies of KD vasculitis lesions have demonstrated characteristic T cell infiltration and an abundance of CD8 T cells; however, the contribution of cytotoxic lymphocytes to KD vasculitis lesions has not been identified. Here, we histopathologically and immunohistochemically examined infiltrating inflammatory cells, particularly cytotoxic protein-positive cells, such as granzyme B cells and TIA-1 cells, in KD vasculitis lesions. Three autopsy specimens with acute-phase KD were observed and contained 24 vasculitis lesions affecting medium-sized muscular arteries, excluding pulmonary arteries. Infiltrating neutrophils in vasculitis lesions were evaluated by hematoxylin and eosin staining, and monocytes/macrophages and lymphocytes were evaluated by immunohistochemistry. The predominant cells were CD163 monocytes/macrophages and CD3 T cells. CD8 T cells, granzyme B cells, and TIA-1 cells were also observed, but CD56 natural killer cells were rare. To the best of our knowledge, the current study is the first histopathologic report confirming the infiltration of inflammatory cells with cytotoxic proteins in vasculitis lesions in patients with KD. Cytotoxic T cells may play a role in the development of vasculitis lesions in KD patients.

The ratio of CD163-positive macrophages to Iba1-positive macrophages is low in the intima in the early stage of cutaneous arteritis.

The etiology of polyarteritis nodosa (PAN) and localized PAN, including cutaneous arteritis (CA), remains unknown; however, initial endothelial damage has been implicated. The intima of the vasculitis lesions is predominantly infiltrated by innate-like bystander-activated CD8 T cells, in addition to the macrophages. Macrophages are among the major inflammatory cells involved in innate immunity and are classified into M1 and M2 subtypes. M1-type macrophages kill pathogens and cause inflammation, while M2-type macrophages promote the repair of tissues. Macrophage subtypes infiltrating in PAN and localized PAN vasculitis lesions have not yet been investigated. Innate immune response to a triggering factor on the endothelial cell surface may initiate CA pathogenesis. Thus, many M1-type macrophages may infiltrate in the intima during early CA. We assessed this hypothesis by immunohistochemical observation of macrophage phenotypes and polarization. Twenty-seven skin biopsy specimens from patients with CA were retrieved. Based on histology, we classified CA into four phases. The phenotypes of infiltrating macrophages in CA were evaluated by immunohistochemistry using antibodies against Iba-1, a pan-macrophage marker, and CD163, an M2-type macrophage marker. Our results showed that the ratio of CD163-positive M2-type macrophages to Iba1-positive macrophages was lower in the intima in the early stage of CA than in the later stage. In the media to adventitia, there was no significant difference in the ratios between these stages. These findings indicate that innate immunity is involved in the intima in the early stage of CA, suggesting that a trigger for CA might exist in endothelial cells.

An anaplastic pleomorphic xanthoastrocytoma with periventricular extension: An autopsy case report and review of the literature.

Pleomorphic xanthoastrocytomas (PXAs) are rare low-grade astrocytic tumors that typically present as superficial nodular cystic tumors of the cerebrum attached to the leptomeninx. Histologically, they are pleomorphic, hypercellular glial neoplasms. Despite the presence of microscopic pleomorphism, patients' postoperative prognosis is generally good. Anaplastic PXAs (APXAs) have a high mitotic index and patients with APXAs have a worse prognosis than patients with PXAs. Here, we report an autopsy case of APXA initially diagnosed as PXA. After gross total resection, the tumor recurred and was diagnosed as an APXA; thereafter, the patient died. An autopsy revealed that the tumor had relapsed at the primary site and had spread to the leptomeningeal space while concurrently invading the cerebrum including the periventricular area forming multifocal lesions. The histological findings of the autopsy were similar to those for epithelioid glioblastoma (EGBM) and small cell glioblastoma (SCGBM). In particular, the periventricular area with multifocal lesions was composed of SCGBM-like cells. It has been shown that multifocal lesions are frequently identified in patients with SCGBM. This is the first histopathologically confirmed case of APXA-related tumor presenting with periventricular extension and multifocal lesion formation. The periventricular extension might be a feature of PXAs and APXAs. However, suspected periventricular spread on imaging in past cases of PXAs and APXAs might instead represent the malignant transformation of these tumors to glioblastoma-like high-grade tumors, which often show SCGBM-like histological patterns.

Acromegaly in preadolescence: A case report of a 9-year-old boy with acromegaly.

BACKGROUND: Acromegaly has been reported in adolescents and young adults, but it is unusual in preadolescence. Diagnosis and management pose different challenges in this age group. Here, we present a rare case of acromegaly in preadolescence. CASE DESCRIPTION: A 9-year-old boy presented with acromegalic features and MRI revealed a pituitary tumor. He was diagnosed as having growth hormone secreting pituitary adenoma based on the multidisciplinary assessment, and underwent gross total tumor resection through an endoscopic endonasal approach (EEA) with subsequent normalization of the hormonal parameters. CONCLUSIONS: Advances in EEA have made safe removal and cure possible even in children. However, long- term follow-up is needed in such younger patients with multidisciplinary management by neurosurgeons, endocrinologists, pediatricians, and ENT surgeons.

Immunostaining With Immunoglobulin G Subclass Antibody Cocktail for Diagnosis of Type 1 Autoimmune Pancreatitis.

BACKGROUND.: Immunoglobulin (Ig) G4-related diseases (RDs) are systemic diseases in which serum IgG4 levels are frequently elevated. They can cause diffuse or focal tumor formation, organ swelling, and tissue thickening in organs infiltrated by IgG4+ plasma cells. The diagnostic criteria for IgG4-RDs include an IgG4/IgG ratio >40%, but counting IgG+ cells can be difficult because of the weakness of IgG staining density. We hypothesized that an antibody cocktail of mixed IgG1, IgG2, IgG3, and IgG4 (AC-IgG) might give immunohistochemistry results comparable with those of IgG in IgG4-RD. METHODS.: We compared AC-IgG reactivity with IgG expression in type 1 autoimmune pancreatitis (AIP), a representative IgG4-RD. We compared immunohistochemistry results using AC-IgG and IgG-only in 10 cases of AIP. The coefficient of variation (Cv) was used to analyze differences between AC-IgG and IgG findings in AIP by 13 board-certified pathologists. RESULTS.: Although mean values for IgG+ cells did not significantly differ between AC-IgG (34.3; range = 27.4-37.1) and IgG (30.0; range = 23.0-45.6; P = .6254), Cv was lower for AC-IgG (33.4%) than for IgG (51.4%; regression equation; y[IgG] = 0.988x + 0.982; correlation coefficient = 0.907). The data showed that the results of both methods were largely consistent. CONCLUSION.: AC-IgG could replace IgG to count IgG+ cells because of its lower Cv.

Ultrastructure of CIC-DUX4 sarcoma: the first pathological report.

CIC-DUX4 sarcoma (CDS) is a recently identified subtype of small round cell sarcoma. Morphologically, CDS partially resembles Ewing sarcoma (ES) and has been classified as "ES-like sarcoma"; however, detailed clinicopathologic and molecular genetic analyses have indicated that CDS is a new independent disease. Many studies have provided light microscopic, immunohistochemical, and genetic information about CDS. However, ultrastructural findings associated with this sarcoma are lacking. The aim of this study was to investigate the ultrastructure of CDS tumors and to compare their features with those of ES. We examined two cytogenetically confirmed CDS cases. We found that, compared to typical ES, CDS presented heterogeneity: in cell density, from tightly packed to loosely unconnected areas; in cell shape, from polygonal to pleomorphic with small processes; and in nuclear shape including round, oval, polygonal, elongated, invaginated, or wrinkled formations. However, abundant glycogen in the cytoplasm and rare cell adhesion apparatus between cells are major similarities between CDS and typical ES. Neuroendocrine granules, which are seen in rare ES cases, could not be identified in these two CDS cases. Although cytogenetic differences can validate a definite diagnosis, ultrastructural features could also provide important information about the differences between CDS and ES.

Malignant peritoneal mesothelioma diagnosed 50 years post-radiotherapy for ovarian cancer in a patient with a history of multiple malignancies: An autopsy case.

As the number of long-term cancer survivors is increasing, the incidence of post-irradiation malignant mesothelioma may also increase. We herein present the case of an 85-year-old female patient with a history of several surgeries for solid tumors and radiotherapy to the pelvis, who presented with abdominal pain and diarrhea. The patient's general condition gradually worsened and she succumbed to cardiopulmonary arrest triggered by vomiting ~3 months after the onset of the abdominal symptoms. An autopsy revealed malignant intestinal obstruction caused by peritoneal mesothelioma. Irradiation is a known risk factor for malignant mesothelioma, which may develop ~10-30 years after radiotherapy. To the best of our knowledge, this is the first report of a patient with malignant mesothelioma developing ~50 years after radiotherapy. The aim of the present study was to remind physicians that malignant mesothelioma should be considered in the differential diagnosis of patients with a history of radiotherapy who present with gastrointestinal symptoms.

A fulminant case of classical Hodgkin lymphoma: A diagnostic dilemma of Epstein-Barr virus-positive large B-cell neoplasms.

We report a fulminant case of classical Hodgkin lymphoma (CHL). The patient died only approximately 2 months after the onset of subjective symptoms. Autopsy specimens revealed atypical cells resembling Hodgkin and Reed-Sternberg (HRS) cells in a rich inflammatory background in various organs. There were marked, characteristic angiodestructive lesions from infiltrating HRS-like cells and numerous macrophages. The HRS-like cells were infected with Epstein-Barr virus (EBV), immunohistochemically positive for PAX5 and CD30, and negative for CD3, CD20, and ALK. Most B-cell markers other than PAX5 were negative, and the HRS-like cells also expressed cytotoxic molecules. Monoclonal rearrangement of immunoglobulin heavy chain was detected by PCR analysis. According to the 2016 WHO classification, we diagnosed mixed cellularity CHL. However, EBV-positive diffuse large B-cell lymphoma (DLBCL), not otherwise specified and EBV-positive B-cell lymphoma, unclassifiable with features intermediate between DLBCL and CHL were considered as differential diagnoses because both tumors are aggressive EBV-positive large B-cell neoplasms with reactive inflammatory cells and sometimes contains HRS-like cells. The clinical condition of the current case was closer to these two entities than to CHL. A diagnosis of EBV-positive large B-cell neoplasms was difficult because of overlapping morphological and immunohistochemical characteristics, but should be considered for prognosis.

Cell biological profiling of reprogrammed cancer stem cell-like colon cancer cells maintained in culture.

Cancer stem cells (CSCs) are specific targets for therapeutic applications, but the rarity of CSCs within tumors makes the isolation of CSCs difficult. To overcome these problems, we generated CSCs in vitro using established reprogramming techniques. We transduced four previously established reprogramming factors, Oct3/4, Sox2, Klf4, and L-myc, into the colon cancer cell lines LoVo and OUMS-23, and investigated the biological characteristics of these lines. Tra-1-60+ cells were obtained from reprogrammed induced pluripotent stem (iPS) cell-like colonies and showed CSC properties, including colony formation, maintenance of colonies by repeated passages, and feeder cell dependency, as well as increased expressions of CSC markers such as CD133 and ALDH1. The CSC-like cells showed increased chemoresistance to 5-fluorouracil and elevated tumorigenicity upon transplantation into kidneys of immune-deficient mice. These tumors shifted to a poorly differentiated stage with many atypical cells, cytoplasmic mucin, and focal papillary components, with demonstrated dedifferentiation. The principal component analysis from DNA microarrays showed that though both cell lines moved to iPS cells after reprogramming, they were not completely identical to iPS cells. Significantly elevated gene expression of Decorin and CD90 was observed in CSC-like cells. Together, these results show that reprogramming of cancer cells produced not pluripotent stem cells but CSC-like cells, and these findings will provide biological information about genuine CSCs and help establish new CSC-targeted therapies.

Myelodysplastic syndrome in an infant with constitutional pure duplication 1q41-qter.

We report on a Japanese female infant as the fourth patient with the constitutional pure duplication 1q41-qter confirmed by chromosomal microarray and as the first who developed myelodysplastic syndrome (MDS) among those with the constitutional 1q duplication. Common clinical features of the constitutional pure duplication 1q41-qter include developmental delay, craniofacial characteristics, foot malformation, hypertrichosis, and respiratory insufficiency. The association between MDS and the duplication of the genes in the 1q41-qter region remains unknown.

First pathological report of a de novo CD5-positive diffuse large B-cell lymphoma patient presenting with Guillain-Barré syndrome-like neuropathy due to neurolymphomatosis.

Peripheral neuropathy occurs in approximately 5% of the patients with lymphoma. Two major causes of peripheral neuropathy associated with lymphoma are neurolymphomatosis and paraneoplastic neuropathy such as demyelinating neuropathy. The differential diagnosis between neurolymphomatosis and demyelinating neuropathy is difficult, because electrophysiological findings suggestive of demyelination are frequently observed even in patients with neurolymphomatosis. Here, we report a patient with de novo CD5-positive diffuse large B-cell lymphoma (DLBCL) who presented with Guillain-Barré syndrome (GBS)-like neuropathy. Demyelination due to paraneoplastic neuropathy was clinically suspected. However, autopsy demonstrated that the cause of the neuropathy was neurolymphomatosis. Clinical courses of neurolymphomatosis vary and neurolymphomatosis cases presenting with GBS-like neuropathy are reported. In addition, DLBCL is the most frequent histological type of malignant lymphoma that develops neurolymphomatosis. Furthermore, "CD5-positive" DLBCL may tend to develop neurolymphomatosis. If a patient with "CD5-positive" DLBCL develops peripheral neuropathy, neurolymphomatosis should be considered and imaging studies performed and, if possible, nerve tissue biopsy, regardless of clinical symptoms of the neuropathy. To our knowledge, this is the first report of a patient with de novo CD5-positive DLBCL with neurolymphomatosis who presented with GBS-like neuropathy.

Usefulness of gastroduodenal biopsy in the differential diagnosis of systemic AH amyloidosis from systemic AL amyloidosis.

AIMS: The aim of this study is to examine the usefulness of gastroduodenal biopsy for the detection of immunoglobulin (Ig) heavy-chain amyloid deposition. Ig heavy-chain amyloidosis (AH amyloidosis) is Ig-related amyloidosis classified together with Ig light-chain amyloidosis (AL amyloidosis). Compared with AL amyloidosis, patients with AH amyloidosis exhibit a better prognosis and they may not need an aggressive treatment. Thus, the accurate diagnosis is essential for management of Ig-related amyloidosis patients. For the definite diagnosis of AH amyloidosis, biochemical analyses are usually needed. However, these analyses are not widely available. Therefore, the characteristic deposition pattern of AH amyloidosis in routine histopathological examination of biopsy specimens, such as gastrointestinal biopsy, if present, may help in the selection of cases for further biochemical analyses. METHODS AND RESULTS: Gastroduodenal biopsy specimens obtained from three cases of biochemically confirmed AH amyloidosis and 21 cases of immunohistochemically confirmed AL amyloidosis were examined, and the following distinctive histopathological features of AH amyloidosis were pointed out: (i) AH amyloid deposition was detectable with Congo red staining in the gastroduodenal biopsy specimens; and (ii) AH amyloid deposition was observed characteristically on the capillary wall of duodenal villi (dotted line-like deposition in the villi), and this pattern was not observed in AL amyloidosis. CONCLUSION: These findings help to select cases for biochemical analyses for definite diagnosis of AH amyloidosis, and may lead to the accumulation of cases and improve our understanding of systemic AH amyloidosis.

In vasculitis of small muscular arteries, activation of vessel-infiltrating CD8 T cells seems to be antigen-independent.

The etiology of polyarteritis nodosa (PAN) and localized PAN is still unknown, although a T cell-mediated immune mechanism has been considered. CD8 T cells participate not only in the antigen-dependent adaptive immune system, but also in the antigen-independent innate immune system. Non-antigen-activated CD8 T cells express a unique phenotype: granzyme B (GrB) positive /CD25 negative /programmed death-1 (PD-1) negative. The aims of this study were to assess the participation of T cells, especially innate CD8 T cells, in the development of vasculitis. Twenty-eight consecutive cases of skin biopsy specimens with cutaneous vasculitis of small muscular arteries (CVSMA) were retrieved. The series comprises of 21 cases of cutaneous arteritis, three cases of PAN, and four cases of rheumatoid vasculitis. Cases of antineutrophil cytoplasmic antibody-associated vasculitis were excluded. The phenotypes of infiltrating lymphocytes in vasculitis lesions were evaluated by immunohistochemistry. In most cases of CVSMA, the number of CD8 T cells infiltrating the intima was higher than that of CD4 T cells, and significant numbers of GrB-positive cells, which represent activated CD8 T cells, were observed. However, GrB/CD25-double-positive cells, which correspond to antigen-activated T cells, were very few in a small number of cases. Cells positive for PD-1, which is also expressed on antigen-activated CD8 T cells, were not detected. We conclude that a T cell-mediated immune mechanism, involving cytotoxic CD8 T cells, may play a role in the development of CVSMA. Low expression of CD25 in activated CD8 T cells suggests that activation was antigen-independent.