c-Kit (CD117) reactivity in extramedullary myeloid tumor/granulocytic sarcoma

Myeloid sarcoma: An overview

Myeloid Sarcoma (MS) is a high grade, hematological malignancy defined as an extramedullary tumor mass of myeloid blasts with or without maturation that effaces tissue architecture. It is a highly heterogenous condition that represents a variety of myeloid neoplasms. This heterogeneity of MS, together with its rarity, have greatly hampered our understanding of the condition. Diagnosis requires tumor biopsy, which should be accompanied by bone marrow evaluation for medullary disease. It is presently recommended that MS be treated similar to AML. Additionally, ablative radiotherapy and novel targeted therapies may also be beneficial. Genetic profiling has identified recurrent genetic abnormalities including gene mutations associated with MS, supporting its etiology similar to AML. However, the mechanisms by which MS homes to specific organs is unclear. This review provides an overview of pathogenesis, pathological and genetic findings, treatment, and prognosis. Improving the management and outcomes of MS patients requires a better understanding of its pathogenesis and its response to various therapeutic approaches.

Pediatric Myeloid Sarcoma, More than Just a Chloroma: A Review of Clinical Presentations, Significance, and Biology

Myeloid sarcomas (MS), commonly referred to as chloromas, are extramedullary tumors of acute myeloid leukemia (AML) with varying incidence and influence on outcomes. Pediatric MS has both a higher incidence and unique clinical presentation, cytogenetic profile, and set of risk factors compared to adult patients. Optimal treatment remains undefined, yet allogeneic hematopoietic stem cell transplantation (allo-HSCT) and epigenetic reprogramming in children are potential therapies. Importantly, the biology of MS development is poorly understood; however, cell-cell interactions, epigenetic dysregulation, cytokine signaling, and angiogenesis all appear to play key roles. This review describes pediatric-specific MS literature and the current state of knowledge about the biological determinants that drive MS development. While the significance of MS remains controversial, the pediatric experience provides an opportunity to investigate mechanisms of disease development to improve patient outcomes. This brings the hope of better understanding MS as a distinct disease entity deserving directed therapeutic approaches.

Myeloid diseases in the lung and pleura

Myeloid diseases detected as primary or secondary lesions in the lung and pleura are rare. Clinical presentations and radiographic results may vary significantly depending on the nature of the diseases. The most common diseases associated with lung and pleura involvement are myeloid sarcoma/acute myeloid leukemia (AML) and extramedullary hematopoiesis (EMH). AML typically represents localized involvement by systemic acute leukemia, while EMH is frequently secondary to underlying benign hematolymphoid disorders or myeloproliferative neoplasms. This review provides an overview of the pathogenesis, clinical presentations, radiologic/imaging studies, pathologic and genetic findings, and treatment/outcomes associated with myeloid diseases in the lung and pleura.

Myeloid Sarcomas Causing Unilateral Cranial Nerve Palsies in a Patient with Relapsed Acute Myeloblastic Leukemia

Myeloid sarcomas (MS) are a rare manifestation of myeloid malignancies and can often be misdiagnosed, leading to a delay in treatment. The objective of this clinical case is to highlight the challenges of the clinical presentation and to emphasize the importance of this manifestation ensuring timely diagnosis and therapy. Here, we present a 43-year-old man who was diagnosed with acute myeloblastic leukemia (AML) after being evaluated for unintentional weight loss, subcutaneous nodules, thrombocytopenia, and anemia. The patient underwent chemotherapy with complete remission and presented 4 months later with dysphagia and cranial nerve palsies. Appropriate imaging and biopsy led to a diagnosis of myeloid sarcoma, and a decision was made to begin reinduction chemotherapy for AML achieving a second complete remission although his neurological deficits did not improve. Our case illustrates the protean presentation of myeloid sarcomas; clinicians should have a high suspicion for MS and remain vigilant when unexplained signs and symptoms arise in the background of a myeloid malignancy although challenges still remain when presentation is de novo. Advancements in understanding the pathophysiology of MS have been performed but remain not completely understood. High clinical suspicion, appropriate imaging, biopsy techniques, and expertise are paramount for timely diagnosis and treatment.

Clinical characteristics and management of primary granulocytic sarcoma of the breast: A case report

RATIONALE

Primary granulocytic sarcoma of the breast is a rare and poor-prognosis malignancy. Clinicians do not have sufficient knowledge of this disease and often misdirect it as other soft tissue sarcomas or inflammation.

PATIENT CONCERNS

A 42-year-old female presented with a self-discovered asymptomatic growing and palpable right breast mass that had been present for 4 months.

DIAGNOSES

The patient was diagnosed as primary myeloid sarcoma.

INTERVENTIONS

The patient received modified radical mastectomy in the right breast and sentinel lymph node biopsy. Pathological diagnosis is primary granulocytic sarcoma. Then the patient accepted acute myeloid leukemia-induction chemotherapy.

OUTCOMES

The follow-up of this patient has no evidence of disease progression or spread during 1 year.

LESSONS

Granulocytic sarcoma in the breast tissue is rare. But it still should be considered in the differential diagnosis of any tumor in the breast. The present study discusses comprehensively the clinical and pathological characteristics to improve the understanding of myeloid sarcoma.

Testicular Myeloid Sarcoma: A Systematic Review of the Literature

Myeloid sarcoma usually involves lymph nodes, and head and neck regions. Uncommon sites like testis and ovary are rarely involved and pose a diagnostic challenge. Nonspecific findings, difficulty in retrieving biopsy specimens, and associated infertility are few of the hurdles faced during diagnosis and treatment of testicular myeloid sarcoma. Our review is an attempt to study myeloid sarcoma involving testis.

Peritoneal Myeloid Sarcoma in a Patient Treated for a Testicular Seminoma

BACKGROUND Myeloid sarcoma is a rare extramedullary soft tissue neoplasm composed of myeloblastic cells, usually associated to hematologic tumor disorders and a poor prognosis. Its diagnosis is very difficult as radiological images are not specific. Histology and immunohistochemistry are necessary for an accurate diagnosis. CASE REPORT We report the case of 46-year-old, Caucasian, non-smoker male, treated in 2014 by orchiectomy and systemic chemotherapy for a stage IIB testicular seminoma. Considering the rapid increase of lactate dehydrogenase (LDH) levels without any evident medical reason, a computed tomography/positron emission tomography (CT/PET) scan was performed and revealing a diffuse, nodular, peritoneal tumor infiltration associated with multiple mesenteric and mediastinal adenopathies. Laparoscopy confirmed a diffuse tumor infiltration of the peritoneum. Histology and immunohistochemistry were consisted with the diagnosis of a myeloid monoblastic sarcoma. Cytology of bone marrow documented an monocytic acute myeloid leukemia. The patient started a systemic induction chemotherapy with high dose cytarabine and idarubicin that was complicated by an infectious pneumonia and colitis, and a grade IV thrombocytopenia leading to a brain subdural hemorrhage and quickly to patient's death. CONCLUSIONS We describe a rare, peritoneal, myeloid sarcoma in a young patient who had been treated by systemic chemotherapy for testicular seminoma 4 years earlier. The patient was clinically asymptomatic and presented only elevated LDH levels without any evident clinical reason. Considering the persistence of this biochemical abnormality, more investigations were performed leading to a diagnosis of peritoneal myeloid sarcoma associated with monocytic acute myeloid leukemia, probably secondary to the past chemotherapy.

Granulocytic Sarcomas: Difficulties in Diagnosis

Granulocytic sarcoma is an uncommon tumor composed of myeloid blasts and/or immature myeloid cells in an extramedullary site which is usually associated with acute or chronic myeloid leukemia. The tumor may also be the initial manifestation of leukemia. The histomorphological diagnosis of granulocytic sarcoma can be challenging to pathologists, especially in the absence of a known hematological disorder. In this case, differentiation of granulocytic sarcoma from malignant lymphomas and other small round cell tumors is very critical. Seven cases of granulocytic sarcoma are reported in this paper. One patient had granulocytic sarcomas at two different sites. Hematoxylin-eosin-stained sections were reexamined. Blastic, poorly differentiated, and well differentiated histopathological variants were found in two, five and one cases, respectively. Immunohistochemical studies were performed on formalin-fixed tissue from all cases using a avidin-biotin-peroxidase complex technique. The panel included antibodies against LCA, CD43, CD34, c-kit, myeloperoxidase, CD68 KP1, CD15, and CD99. All cases stained positively with LCA, CD43, CD34, myeloperoxidase, and CD68. Five cases were positive for c-kit, three cases were positive for CD15, and two cases were positive for CD99. An immunohistochemical panel including at least myeloperoxidase, CD68 and CD34 can be used for detection of myeloid differentiation. It is also important that granulocytic sarcoma be considered in the differential diagnosis of CD99-positive round cell tumors.

Do Not Forget the Glycophorin A: An Unusual Case of Myeloid Sarcoma

Acute erythroid leukemia is rare, with isolated reports on presentation as an extramedullary tumor mass (myeloid sarcoma). We describe a case of pure erythroid leukemia presenting as an orbital mass in a 1-year, 9-month-old girl. This is only the second case described in a child. Tissue biopsy of the tumor mass showed medium-sized cells that were glycophorin A positive and negative with conventional myeloid markers. Flow cytometry, bone marrow aspirate, and trephine confirmed the diagnosis of pure erythroid leukemia.

Evaluation of tyrosine-kinase receptor c-kit mutations, mRNA and protein expression in canine lymphoma: might c-kit represent a therapeutic target?

c-kit plays an important role in proliferation, survival and differentiation of hematopoietic progenitor cells. In human hematopoietic malignancies, c-kit is mostly expressed by progenitor cell neoplasms and seldom by mature cell neoplasms. Aim of this study was to evaluate c-kit expression in canine lymphoma. Twenty-five B-cell lymphomas and 21 T-cell lymphomas were enrolled in the study. c-kit mRNA and protein expression was measured in lymph node fine needle aspirates by quantitative real-time RT-PCR, flow cytometry and immunocytochemistry, while the occurrence of KIT mutations on exons 8-11 and 17 was investigated by direct cDNA sequencing. KIT mRNA was amplifiable but below the limit of quantification in 76% of B-cell lymphomas and 33% of T-cell lymphomas. Remaining samples showed a very low expression of KIT, except for some high grade (HG) T-cell lymphomas where a comparatively higher mRNA amount was observed. Transcriptional data were confirmed at the protein level. No gain-of-function mutations were observed. Among canine lymphomas, T-cell lymphoma typically shows an aggressive biological behavior, partly being attributable to the lack of efficacious treatment options, and the evidence of c-kit expression in HG T-cell lymphomas might represent the rationale for its routinely diagnostic evaluation and the use of tyrosine kinase inhibitors in future clinical trials.

Granulocytic sarcoma of the male breast in acute myeloblastic leukemia with concurrent deletion of 5q and trisomy 8

We describe a unique case of Granulocytic Sarcoma (GS) in a male, who presented to us with a painless right breast mass without any prior history of Leukemia. GS is an extramedullary tumor of myeloproliferative precursors and may involve multiple sites of the body, but involvement of male breast is extremely rare. In the absence of clinical history or hematological abnormality, GS may be misdiagnosed, depending on the degree of myeloid differentiation present within the tumor. Often it is misdiagnosed as lymphoma. Diagnosis is made by finding eosinophilic myelocytes, myeloperoxidase, chloroacetate esterase staining, and lysozyme immunostain. Chemotherapy regimens similar to acute myeloid leukemia are recommended to treat GS. Recognition of this rare entity is important because early, aggressive chemotherapy can induce regression of the tumor and improve patient longevity.

Aleukemic granulocytic sarcoma presenting at multiple sites: ovary, breast and soft tissue

An 18 year old female presented with the history of pain in abdomen, breast engorgement, swelling over both legs and breathlessness for three month. On clinical examination diagnosis of fibroadenoma breast was made. Ultrasonography of abdomen showed bilateral ovarian mass. Bilateral salpingo-ophrectomy was done and specimen was sent for histological examination. Two lobulated solid masses of tissues the larger one measuring 13×8×5 cm and smaller one measuring 10×7×5 cm in size received. Microscopic examination showed monomorphic population of discohesive, hyperchromatic small round cells had high N:C ratio, coarse chromatin, conspicuous nucleoli and scant to moderate amount of basophilic cytoplasm, lying in sheets and separated by fibrous strands and diffusely infiltrating the ovarian stroma. Fine needle aspiration from breast lump and leg swelling showed predominant population of blast cells. Myeloperoxidase was strongly positive and diagnosis of granulocytic sarcoma was confirmed.

Post-tonsillectomy pulmonary complication in a patient with tonsillar myeloid sarcoma

Myeloid sarcoma in a patient with myelodysplastic syndrome (MDS) manifesting as a non-healing tonsillar ulcer is an extremely rare occurrence. We report the case of a 57-year-old male smoker with a non-healing tonsillar ulcer who underwent tonsillectomy to rule out tonsillar carcinoma after failed antibiotic therapy. On postoperative day 2, he presented with a temperature of 40°C and white blood cell count of 34700/μL. Antibiotic therapy was begun; however, he died 1 day later due to pulmonary infection and septic shock. Though extremely rare, tonsillar involvement of MDS should be considered in the differential diagnosis of a non-healing tonsillar lesion. When definitive diagnosis requires a tissue sample, punch biopsy may be preferable to tonsillectomy in a patient who may be immunocompromised, and appropriate prophylactic antibiotics should be administered.

Cytophagic and S-100 protein immunoreactive myeloid leukemia cutis

Myeloid leukemia cutis (LC) is the cutaneous involvement by neoplastic leukocytes of the myeloid series. Myeloid LC may occur de novo or concurrently with acute myeloid leukemias, chronic myeloid leukemias, other myeloproliferative disorders or myelodysplastic syndromes. We describe an unusual case of cytophagic S-100 protein immunoreactive leukemia cutis presenting in an 87-year-old woman without prior history of myeloid leukemia or other hematologic disorders. We outline key histologic and immunohistochemical features that aide in the diagnosis of LC. The presence of cytophagocytosis on histologic examination, a phenomenon more commonly associated with lymphoid rather than myeloid malignancies, provided a clue to the possibility of a malignant process. The atypical myeloid infiltrate showed S-100 protein positivity, an unusual finding that may be seen in LC. Although not commonly reported in LC, the presence of S-100 protein positivity and cytophagocytosis should not lead to the premature exclusion of LC as a possible diagnosis until a thorough clinical, histologic and immunohistochemical evaluation is performed. In addition, the presence of cytophagocytosis has been shown to have prognostic significance for patients with myeloid leukemia.

Granulocytic sarcoma of the breast without development of bone marrow involvement: a case report

A 29-year-old woman presented with a breast tumor with a primary diagnosis of MALT lymphoma. A repeat biopsy revealed a hematological neoplasm with diffuse, Indian file, and targetoid patterns. The cells were intermediate size with eosinophilic granules; the immunophenotyping showed monocytic differentiation, and no lymphoepithelial lesion was observed. The diagnosis was granulocytic sarcoma. Three different bone marrow biopsies were negative for neoplastic infiltration. After treatment, she developed secondary pancytopenia which contributed to her death 16 months after primary diagnosis. Granulocytic sarcoma of the breast is uncommon. A complete panel of immunohistochemistry is necessary to perform this diagnosis.

Granulocytic sarcoma: 32 cases and review of the literature

Thirty-two cases of granulocytic sarcoma (GS) are reported in this paper. Age range was from 16 - 70 years. GS was accompanied by AML in 13 cases, ALL (My+) in one case, CML in 11 cases and MDS in two cases. GS was diagnosed simultaneously with leukemia in five cases and preceded the leukemia in eight. Lymph node and soft tissue were the most commonly detected localizations. Seven cases had first been diagnosed as NHL. Histopathologically blastic, immature and mature variants were found in 11, nine and 11 cases respectively and overall survival was shortest in the blastic type. Myeloperoxidase and lysozyme were found to be positive in 30 and 24 cases respectively. Therapy was radiation in five cases and surgery in three. Systemic chemotherapy was given to the cases. The clinical outcome of the patients after the diagnosis of GS was poor. GS is a unique entity; prognosis is poor but it is important to detect the signaling pathways associated with migration of myeloid cells to the extra-medullary tissues. The critical factors for detecting this interesting tumor are to be aware of this disease, cooperation between clinician and pathologist and the application of special stains to detect the myeloid origin.

Benign extramedullary myeloid proliferations

Extramedullary proliferations of bone marrow elements are infrequently encountered in routine pathology practice. On occasion, they can present diagnostic difficulties when seen in unusual or unanticipated sites. This review serves to cover aspects of underlying embryogenesis of myeloid elements, as well as sites and circumstance of benign proliferations of myeloid elements along with their occasional confusion with neoplastic myeloid proliferations. Benign proliferations associated with hematologic disorders and hematopoietic growth factors are discussed. Immunohistochemical evaluation of myeloid proliferations is considered as well.

Gastrointestinal stromal tumors: differential diagnosis

Availability of KIT tyrosine kinase inhibitors for specific treatment of GISTs has magnified the importance of accurate differential diagnosis of GIST from other tumors occurring in the GI tract and abdomen. The general problems in this distinction include histological mimicry of other mesenchymal tumors with GIST, occasional KIT-negativity of GIST, and KIT-positivity of non-GISTs. Up to 5% to 10% gastric GISTs and <2% of intestinal GISTs can be KIT-negative. The identification of these tumors as GISTs is based on knowledge of the spectrum of GIST morphology, and can be supported by molecular diagnosis of KIT and PDGFRA mutations (the latter pertain to gastric tumors). True smooth muscle tumors (rare in GI tract except in esophagus and colon) can be separated from GISTs by the eosinophilic tinctorial quality of tumor cells, positivity for smooth muscle markers, and negativity for KIT. Desmoids can form large GIST-like masses, but are composed of spindled or stellate-shaped cells in a densely collagenous stroma. Negativity for KIT and nuclear positivity for beta-catenin are differentiating features. GI schwannomas, melanoma, and rare primary clear cell sarcoma are S100-positive, usually with characteristic histology. The latter two can be KIT-positive. KIT-positive non-GISTs include some sarcomas, especially angiosarcoma and Ewing sarcoma, extramedullary myeloid tumor, seminoma, and a few carcinomas, notably small cell carcinoma of lung. Spurious KIT-positivity, seen with some polyclonal KIT antibodies, has been a source of confusion leading to probable false-positive results in fibroblastic tumors and occasional other sarcomas, such as leiomyosarcomas. Integration of histological features with carefully standardized immunohistochemistry, supported by KIT and PDGFRA mutation analysis, is the cornerstone of state-of-the art differential diagnosis of GIST. To comprehensively capture all GISTs, KIT immunostains should be performed on all unclassified epithelioid and mesenchymal tumors of the abdomen. This is a US government work. There are no restrictions on its use.

Myeloid sarcoma presenting with bilateral proptosis and kidney infiltration

The authors describe a male infant with a history of transient pancytopenia who developed progressive bilateral proptosis associated with diffuse infiltration of the kidney and normal bone marrow. The histopathological examination of the kidney revealed diffuse infiltration of cells of myeloid origin with monocytic differentiation. Although orbital involvement by myeloid sarcoma, with or without concurrent acute myeloid leukemia, is well known, there are distinctive features in this patient that are not reported in the literature, namely bilateral proptosis and simultaneous presence of bilateral kidney infiltration, which enabled diagnosis.

Disseminated extramedullary myeloid tumor of the gallbladder without involvement of the bone marrow

Extramedullary myeloid tumors (myeloid sarcomas) are rare neoplasms that are composed of myeloid precursors. They usually arise concurrently with a diagnosis of acute myeloid leukemia, chronic myeloid leukemia, or other myeloproliferative disorders. They may also indicate relapsing disease in a patient with a prior history of leukemia or myeloproliferative disorder. We present our findings of a 63-year-old female diagnosed with extramedullary myeloid tumor first presenting in the gallbladder. She subsequently developed respiratory failure; pre- and postmortem bone marrow studies were negative for leukemia by morphology, flow cytometry, and karyotypic analysis. However, the myeloid neoplasm was disseminated throughout most of her remaining organs. Immunohistochemical stains of the cells indicated a neoplasm of myelomonocytic derivation (CD4, CD43, CD45, CD68, myeloperoxidase, and lysozyme positive). To our knowledge, this is the first report of an extramedullary myeloid neoplasm of the gallbladder with disseminated disease without involvement of the bone marrow.

Myeloid sarcoma: clinico-pathologic, phenotypic and cytogenetic analysis of 92 adult patients

Myeloid sarcoma (MS) is a rare neoplasm whose knowledge is largely based on case reports and/or technically dated contributions. Ninety-two MSs in adulthood with clinical data available were evaluated both morphologically and immunohistochemically. Seventy-four cases were also studied by fluorescent in situ hybridization on tissue sections and/or conventional karyotyping on bone marrow or peripheral blood. Histologically, 50% of the tumors were of the blastic type, 43.5% either monoblastic or myelomonocytic and 6.5% corresponded to different histotypes. CD68/KP1 was the most commonly expressed marker (100%), followed by myeloperoxidase (83.6%), CD117 (80.4%), CD99 (54.3%), CD68/PG-M1 (51%), CD34 (43.4%), terminal-deoxy-nucleotidyl-transferase (31.5%), CD56 (13%), CD61/linker for activation of T cells (2.2%), CD30 (2.2%) and CD4 (1.1%). Foci of plasmacytoid monocyte differentiation were observed in intestinal cases carrying inv16. Chromosomal aberrations were detected in about 54% of cases: monosomy 7(10.8%), trisomy 8(10.4%) and mixed lineage leukemia-splitting (8.5%) were the commonest abnormalities, whereas t(8;21) was rare (2.2%). The behavior was dramatic irrespective of presentation, age, sex, phenotype and cytogenetics. Most if not all, long survivors received bone-marrow transplantation. The present report expands the spectrum of our knowledge showing that MS has frequent monoblastic/myelomonocytic differentiation, displays distinctive phenotypic profile, carries chromosomal aberrations other than t(8;21), and requires supra-maximal therapy.

Myeloid sarcoma of the extrahepatic bile ducts presenting as obstructive jaundice

We report a rare case of myeloid sarcoma (MS) of the extrahepatic bile ducts presenting as obstructive jaundice in a patient without leukemia at time of diagnosis. A 75-year-old female presented with a one-month history of abdominal pain and jaundice. Computerized tomography scan of the abdomen showed stenosis of the extrahepatic bile ducts. Endoscopic retrograde cholangiography disclosed an irregular narrowing of the common biliary duct, suggestive of a cholangiocarcinoma, and resection was performed. Histologic examination showed diffuse transmural infiltration of malignant cells. These cells exhibited medium-sized round nuclei with central nucleoli and eosinophilic cytoplasm, and were strongly positive for myeloperoxidase, CD68, lysozyme, CD45, CD117 (c-kit protein) and CD43. Eight months following surgery the patient presented with multiple cutaneous nodules and bone marrow trephine biopsy showed acute myelomonocytic leukemia. A literature search identified two previously reported cases of MS of the extrahepatic biliary duct. MS should be taken into consideration in the differential diagnosis of a patient with obstructive jaundice. Immunohistochemistry is essential for a correct diagnosis.

KIT (CD117): a review on expression in normal and neoplastic tissues, and mutations and their clinicopathologic correlation

CD117 (KIT) is a type III receptor tyrosine kinase operating in cell signal transduction in several cell types. Normally KIT is activated (phosphorylated) by binding of its ligand, the stem cell factor. This leads to a phosphorylation cascade ultimately activating various transcription factors in different cell types. Such activation regulates apoptosis, cell differentiation, proliferation, chemotaxis, and cell adhesion. KIT-dependent cell types include mast cells, some hematopoietic stem cells, germ cells, melanocytes, and Cajal cells of the gastrointestinal tract, and neoplasms of these cells are examples of KIT-positive tumors. Other KIT-positive normal cells include epithelial cells in skin adnexa, breast, and subsets of cerebellar neurons. KIT positivity has been variably reported in sarcomas such as angiosarcoma, Ewing sarcoma, synovial sarcoma, leiomyosarcoma, and MFH; results of the last three are controversial. The variations in published data may result from incomplete specificity of some polyclonal antibodies, possibly contributed by too high dilutions. Also, KIT is expressed in pulmonary and other small cell carcinomas, adenoid cystic carcinoma, renal chromophobe carcinoma, thymic, and some ovarian and few breast carcinomas. A good KIT antibody reacts with known KIT positive cells, and smooth muscle cells and fibroblasts are negative. KIT deficiency due to hereditary nonsense/missense mutations leads to disruption of KIT-dependent functions such as erythropoiesis, skin pigmentation, fertility, and gastrointestinal motility. Conversely, pathologic activation of KIT through gain-of-function mutations leads to neoplasia of KIT-dependent and KIT-positive cell types at least in three different systems: mast cells/myeloid cells--mastocytosis/acute myeloid leukemia, germ cells--seminoma, and Cajal cells--gastrointestinal stromal tumors (GISTs). KIT tyrosine kinase inhibitors such as imatinib mesylate are the generally accepted treatment of metastatic GISTs, and their availability has prompted an active search for other treatment targets among KIT-positive tumors such as myeloid leukemias and small cell carcinoma of the lung, with variable and often nonconvincing results.

CD117 expression in diffuse large B-cell lymphomas: fact or fiction?

CD117 (KIT) is expressed in a variety of hematopoietic neoplasms but there are a paucity of data regarding its expression in diffuse large B-cell lymphomas (DLBCL). The purpose of the present paper was to describe the authors' experience of two CD117+ DLBCL (one of follicle center-cell origin and one nasal Epstein-Barr virus (EBV)- plasmablastic lymphoma associated with lytic bone lesions), as determined by tissue immunohistochemistry and flow cytometry. The CD117 expression in DLBCL was further evaluated using tissue microarrays and seven additional plasmablastic lymphomas, using two commercially available anti-CD117 antibodies (Ab-1, Oncogene and A4502, DakoCytomation). Membranous +/- cytoplasmic staining was seen with Ab-1 in 24/65 (37%) DLBCL, including 21/56 microarray DLBCL, two index cases, and 1/7 additional plasmablastic lymphomas, with persistent staining in 13% of microarray DLBCL despite preincubation with KIT peptide. However, A4502 had only membranous staining of the index cases and one additional EBV- plasmablastic lymphoma with medullary disease. The present study suggests that (i) CD117 expression can be detected sporadically in DLBCL of follicle center-cell origin and a subset of plasmablastic lymphomas; (ii) staining for CD117 might help in identifying EBV- plasmablastic lymphomas associated with bone marrow involvement; and (iii) CD117 antibodies should be carefully validated prior to use, because non-specific staining, as observed with Ab-1, could lead to false-positive results.

Granulocytic sarcoma of the spine in a child without bone marrow involvement: a case report and literature review

We report a 2-year-old Japanese boy without bone marrow involvement who developed a primary granulocytic sarcoma in his spinal canal. Tumour cells were positive for myeloperoxidase, MIC2, CD56 and, CD68 on formalin-fixed, paraffin-embedded tissue sections and CD13, CD33, CD45, and CD64 on acetone-fixed fresh frozen sections. Nine months after the initiation of treatment, the tumour had significantly regressed and the patient was able to walk with help.

CONCLUSION

Our patient is the youngest case of granulocytic sarcoma of the spine without bone marrow involvement. Immunohistochemical methods are very helpful in establishing a diagnosis of granulocytic sarcoma.

Granulocytic sarcoma presenting as bilateral adrenal masses

Granulocytic sarcoma (GS) is a collection of immature myeloid cells contained outside the bone marrow often seen in association with acute myeloid leukemia or as a sign of leukemic transformation in myeloproliferative disorders. Rarely, GS is an isolated finding unaccompanied by another hematological disorder. GS can occur at a variety of sites, most commonly involving the bone, soft tissue, lymph nodes, or skin. We report GS presenting as bilateral adrenal masses in a patient without an antecedent hematologic illness.

Myeloid sarcoma occurring in the maxillary gingiva: a case without leukemic manifestations

Myeloid sarcoma (MS) is a localized extramedullary mass of immature granulocytic cells that usually occurs in patients with acute myeloid leukemia (AML) or myeloproliferative disorders. It may rarely precede peripheral blood or bone marrow involvement, presenting a diagnostic challenge. Although MS may be found in any location, an intraoral occurrence is rare. In this report we describe a rare case of a patient with nonleukemic MS of the maxillary gingiva. The histologic specimen was first interpreted as non-Hodgkin's lymphoma. The correct diagnosis was reached after extensive immunohistologic studies. The malignant cells were myeloperoxidase positive, lysozyme positive, CD45+, CD68+, CD3-, CD10-, CD19-, CD20-, CD30-, CD34-, CD56-, CD79a-, S100-, and chloroacetate esterase negative. Induction therapy with FLAND (fludarabine, Ara-C, mitoxantrone, and dexamethasone) was started, but the patient did not achieve a remission. Some weeks later, the patient presented pleural effusion and paralysis of the seventh cranial nerve on the left side. She died a few days later. The present case indicates the importance of a correct initial diagnosis for adequate therapy, which is often delayed because of a high misdiagnosis rate. If the MS is treated without intensive chemotherapy for AML as soon as possible, the prognosis will be poor.

Extramedullary myeloid tumour (EMMT) of the gallbladder

This report describes a rare case of an extramedullary myeloid tumour (EMMT) of the gallbladder in a patient without leukaemia. A 33 year old man visited a local hospital because of jaundice. Abdominal computed tomography revealed a tumorous mass measuring 6.0 x 4.5 cm and involving the entire gallbladder. A percutaneous needle biopsy was attempted, but because adenocarcinoma could not be completely ruled out, the use of undue force was considered dangerous. Under a preoperative diagnosis of gallbladder carcinoma, a hepatopancreatoduodenectomy was performed. The tumour cells exhibited various amounts of eosinophilic cytoplasm, had medium sized round nuclei with indentation and grooving, and were strongly immunoreactive for myeloperoxidase, CD43, and c-kit protein (CD117). After surgery, the patient underwent combination chemotherapy as prescribed for cases of acute myeloblastic leukaemia. The patient did not develop acute leukaemia during a follow up period of four years. In conclusion, a correct diagnosis of EMMT can be made using appropriate immunohistochemical staining.

[A-leukemic caecal myeloid sarcoma: a difficult diagnosis]

Myeloid sarcoma is a malignant neoplasia composed of abnormal myeloid or monocytic cells, often localized in bones, but also rarely in extra-medullary sites such as lymph nodes, skin and soft tissue. We report a case of caecal myeloid sarcoma, diagnosed in a 60 year old woman who complained from abdominal pain and weight loss, in absence of any medullary disorder. Initially misdiagnosed as a B lymphoma because of a weak positivity for CD79a, the diagnosis of primitive caecal myeloid sarcoma was eventually established after further investigations showing a positivity for lysozyme and myeloperoxidase. This report of such a rare clinical and pathological presentation of a myeloid sarcoma underlines a difficult differential diagnosis for which adequate immunohistochemistry, including lysozyme and myeloperoxydase is mandatory.

Myeloid Sarcoma Involving the Breast

Context.—Myeloid sarcoma is a neoplasm of myeloid cells that can arise before, concurrent with, or following acute myeloid leukemia. Rarely, it can also occur as an isolated mass.

Objective.—To describe the clinicopathologic features of 6 patients with myeloid sarcoma involving the breast.

Design.—Clinical information for all 6 patients was obtained from the medical record. Routine hematoxylin-eosin–stained slides; naphthol AS-D chloroacetate stain; and immunohistochemical stains for myeloid, B-cell, and T-cell antigens were prepared.

Results.—There were 6 women with a median age of 52 years (range, 31–73 years). Two patients presented with isolated tumors of the breast, with no history or subsequent development of acute myeloid leukemia. In 3 patients, the breast tumors represented relapse of acute myeloid leukemia. One patient who presented initially with myeloid sarcoma involving the breast, skin, and spleen was lost to follow-up. Histologically, these tumors were classified as well differentiated (n = 3), poorly differentiated (n = 2), and blastic (n = 1). Naphthol AS-D chloroacetate esterase was positive in all 3 cases assessed. Immunohistochemistry showed that myeloperoxidase (n = 5) and CD43 (n = 3) were positive, and CD3 (n = 5) and CD20 (n = 5) were negative in all cases assessed. Lysozyme was positive in 4 (80%) of 5; CD117 was positive in 2 (67%) of 3; and single cases were positive for CD45 (1/3), TdT (1/2), CD79a, and the PAX5 gene product.

Conclusions.—Myeloid sarcoma involving the breast is uncommon. In the literature, as in this study, these tumors most often represent relapse or the initial presentation of acute myeloid leukemia. However, 2 of the cases we report presented with isolated masses, without a history or subsequent development of acute myeloid leukemia at last follow-up. Immunohistochemical studies are extremely helpful for recognizing isolated myeloid sarcoma.

Chloroma of the Testis After Allogeneic Peripheral Blood Stem Cell Transplantation: A Case Report

Chloroma, or granulocytic sarcoma, is a rare extramedullary solid hematologic cancer that affects many sites, usually in concert with acute myeloid leukemia. It is infrequently associated with other myeloproliferative disorders or chronic myelogenous leukemia. Chloroma of the testis after allogeneic bone marrow transplantation is particularly sparsely represented in the literature. It is often incorrectly diagnosed as malignant lymphoma, especially large-cell lymphoma, owing to the similarity of the histologic morphology, scanty eosinophilic myelocytes, and no or overlooked history of leukemia. Although erroneous diagnosis is decreasing with the advent of ancillary studies, the diagnosis of chloroma continues to be a nightmare for pathologists. It is thus suggested that an appropriate panel of marker studies be performed in conjunction with clinical correlation and circumspection to avoid reaching a misleading conclusion and improper treatment of patients. We report an interesting case of a 35-year-old male with a clinical history of chronic myelogenous leukemia post allogeneic peripheral blood stem cell transplantation and complete molecular remission, who was found to have chloroma of the left testis.

Extramedullary hematopoietic proliferations, extraosseous plasmacytomas, and ectopic splenic implants (splenosis)

Hematopoietic proliferations are well known to present ectopically outside the bone marrow, either in benign or malignant form. As such, they present a distinct problem with respect to morphologic interpretation because of their uncommonality in extramedullary sites and their capacity to simulate other lesions histologically. This review considers extramedullary myeloid tumors ("granulocytic sarcoma," "erythroblastic sarcoma," "megakaryocytic sarcoma"), tumefactive extramedullary hematopoiesis, and the peculiar condition known as "splenosis," with consideration of their clinical, microscopic, and cytohistochemical chararacteristics.

Immunohistochemistry in gynecological pathology

Although the majority of diagnoses in gynecological pathology are established on examination of routine hematoxylin and eosin stained sections, additional tests are occasionally required. Immunohistochemistry is widely used to provide additional diagnostic information in problematic cases. This review touches on some of the basics of the procedure, presents an example immunohistochemical panel, and discusses some of the most common immunohistochemical markers used in diagnostic gynecological pathology. Differential diagnostic problems and relevant immunohistochemical stains for the vulva, vagina, cervix, uterus, and ovary are also addressed.

CD117 (KIT receptor) expression in Merkel cell carcinoma

The KIT receptor tyrosine kinase (CD117 antigen) is found in a variety of normal tissue cell types and in several malignant tumors, including acute myeloid leukemia. We recently encountered two tumors initially suspected as acute myeloid leukemia cutis and expressing CD117 that showed punctate positivity for cytokeratin 20 diagnostic for Merkel cell carcinoma. We evaluated 20 additional cases of MCC and found that 21 of 22 tumors (95%) expressed CD117. Intensity of CD117 expression did not appear to correlate with aggressive behavior. While the function of the KIT receptor in MCC is not known, its pathogenic role in other malignant neoplasms suggests the possibility of a similar role in MCC.