Myeloid Sarcoma Involving the Breast

Solitary eosinophilic granulocytic sarcoma in a dog

A 6-year-old male golden retriever presented with swelling of the left upper eyelid of 2 months duration, which did not improve following a course of antibiotics. Routine serum biochemistry, complete blood count and diagnostic imaging identified no clinically significant abnormalities. The mass was surgically excised, and histopathologic examination was performed. Eosinophilic granulocytic sarcoma (GS) was diagnosed based on the results of histopathology and immunohistochemistry. This is the first report of GS affecting the eyelid of a dog.

Role of 18 F-FDG-PET/CT in an AML-M5a Subtype Patient with Rare Constellation of Hemophagocytic Lymphohistiocytosis & Bilateral Multiple Breast Chloromas

We report a treated case of acute myeloid leukemia (AML-M5a subtype) with monocytic differentiation (AMoL) presenting with fever and body pains. Initial 18 F-FDG-PET/CT ( 18 F-flurodeoxyglucose positron emission tomography/computed tomography) identified multiple lymph nodal, and marrow lesions. Biopsy confirmed hemophagocytic lymphohistiocytosis (HLH). Post HLH treatment, follow-up PET/CT demonstrated unsuspected FDG avid bilateral breast lesions ( n  = 5), which proved to be chloromas, that is, extranodal manifestation of AML. 18 F-FDG-PET/CT has helped not only in identifying the various sites of disease involvement but also in guiding the sites for biopsy. Finally, 18 F-FDG-PET/CT was useful in monitoring therapy response for both these coexisting pathologies, which are said to be resistant to treatment based on FLT3-ITD tyrosine kinase-3 internal tandem duplication mutation positivity and high-grade AML status. This case represents a rare constellation of different etiologies that needed to be differentiated. It also emphasizes the challenges in interpreting PET/CT findings, especially in difficult clinical scenarios. Disease distribution in HLH/presence of chloromas, etc., can mimic stage IV lymphoma in a known case of AML. So the nuclear medicine physician should be aware of the different complications in the background of AML, especially in patients with poor prognostic factors.

Case report: The first case of concurrent breast myeloid sarcoma and borderline phyllodes tumor with malignant features

Background

Myeloid sarcoma (MS) is a rare hematological malignancy characterized by the formation of a solid mass of myeloblasts outside the bone marrow, such as in the lymph nodes, skin, or bone. MS may arise de novo or concurrently with acute myeloid leukemia (AML), myeloproliferative neoplasm (MPN), or myelodysplastic syndrome (MDS). MS accounts for less than 1% of extramedullary acute myeloid leukemia cases. Phyllodes tumors (PTs) are a rare fibroepithelial breast tumor that can be benign, malignant, or borderline, and account for less than 1% of all breast cancers.

Case presentation

We present a unique case of a 50-year-old woman with both breast MS and borderline PT with malignant features, which presented a diagnostic challenge. The patient initially presented with a mass in her right breast, and the initial fine-needle biopsy revealed the presence of immature myeloperoxidase (MPO)+ myeloid cells consistent with MS. Subsequent pathological analysis of tumor tissues after neoadjuvant radiotherapy and chemotherapy showed a borderline PT with malignant features. Following excision of the tumor, the patient experienced a local recurrence, which was also surgically removed. At 8 months post-surgery, the patient remains free of recurrence under close follow-up.

Conclusion

This case highlights the importance of considering the possibility of concurrent malignancies in the differential diagnosis of complex breast masses and underscores the challenges involved in diagnosing and managing such cases. Additionally, we also emphasize the value of neoadjuvant radiotherapy and chemotherapy in MS.

Breast Recurrence of Acute Myeloid Leukemia After Bone Marrow Transplantation: A Case Report About Myeloid Sarcoma of the Breast

Myeloid sarcoma of the breast is a rare malignancy, can be seen after bone marrow transplantation. Although there are no specific features for this malignancy which is difficult to diagnose, some common features draw attention in the published case reports. Since there is no consensus on the treatment of myeloid sarcoma of the breast, we aimed to explain our own diagnosis and treatment methods in this case report.

Myeloid sarcoma of the breast: a pathology that should not be forgotten

Myeloid sarcoma (MS) is a rare neoplasm, represented by a tumoural mass composed of myeloid blasts, occurring at any anatomical site other than the bone marrow. MS is considered the tissue-based equivalent of acute myeloid leukaemia (AML), requiring the same therapeutic specification, independently from the association with previous or coexisting myeloid neoplasms. Isolated breast involvement by MS is exceedingly rare, with only exceptional cases reported in the literature. This work aims to provide a pictorial essay of the main features of breast involvement by MS. Even though it is a rare condition, we should not forget this neoplasm, and its possibility of being disguised by the AML, as it requires prompt treatment.

Challenges associated with limited-resources cancer care facility: Bilateral breast myeloid sarcoma as an example

Myeloid sarcoma (MS) is a rare myeloid malignancy. It can arise before, concurrent with, or following different malignant hematological diseases, most commonly acute myeloid leukemia (AML), myelodysplastic syndrome, or myeloproliferative neoplasms. Here we describe a 30-year-old female with AML-M1 who presented to the hematology department with bilateral breast pain and tenderness. Available diagnostic measures including ultrasound of breast and magnetic resonance imaging were used to determine the nature of these breast lumps. MS was definitively diagnosed via biopsy and the patient was treated with systemic chemotherapy. Despite her AML treatment she unfortunately died secondary to disease progression. The authors consider this case of particular educational value due to the bilateral and aggressive nature of this patient's disease in the setting of a cancer-care facility with limited resources.

KEY CLINICAL MESSAGE

In retrospect, if breast MS had been considered earlier in this patient's presentation, a referral to an outside center with matched stem cell transplantation capability may have been warranted after complete remission following first bone marrow relapse, rather than continuing chemotherapy alone.

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.

Sonographic Features of a Myeloid Sarcoma of the Breast as a Relapse of Acute Myeloid Leukemia After Stem-Cell Transplantation: A Case Report

Patient: Female, 24

Final Diagnosis: Myeloid sarcoma of the breast

Symptoms: Breast lump

Medication: —

Clinical Procedure: Core needle biopsy

Specialty: Radiology

A unique clinical presentation of de novo acute promyelocytic leukemia as a myeloid sarcoma of the breast

Myeloid sarcoma is a rare presentation of acute leukemia as a solid tumor at various extramedullary sites. It may present concurrently, before or after the onset of systemic bone marrow leukemia. Unusual clinical localization may lead to misdiagnosis, or delayed diagnosis and treatment. We describe the first case, to our knowledge, of de novo myeloid sarcoma of the breast confirmed as acute promyelocytic leukemia. Immunohistochemical analysis, flow cytometry, fluorescent in situ hybridization analysis and molecular analysis using RQ-PCR of tissue samples should be routine in determining the correct diagnosis in this setting.

Fine-needle aspiration cytology of granulocytic sarcoma presenting as a breast lump - Report of a rare case with a comprehensive literature search

Myeloid sarcoma is a neoplasm of myeloid cells that can arise before or concurrent with or may follow acute myeloid leukemia. Very rarely, it can present as an isolated breast lump. We have diagnosed a case of myeloid sarcoma by fine-needle aspiration cytology (FNAC), in a 52-year-old woman who presented with the right-sided breast lump. FNAC showed hypercellular smears with immature myeloid cells few neutrophils and many large round cells with high nuclear-cytoplasmic ratio, prominent nucleoli and a moderate amount of granular cytoplasm. The blast cells were myeloperoxidase positive and complete blood count, and peripheral blood examination were normal. We report this case for its rarity and as a note of caution to a pathologist to consider myeloid sarcoma in the differential diagnosis of breast lump to provide the correct diagnosis and avoid incorrect treatment of a curable disease.

Granulocytic Sarcoma Presenting as a Palpable Breast Lump

We report the case of a 45-year-old woman who palpated a voluminous painless lump in the superior outer quadrant of her left breast. Her past medical history revealed an acute myeloid leukemia (AML) treated and considered in remission 1 month prior to this discovery. Imaging work-up by mammogram, US, and MRI showed multiples masses suspect of malignancy in both breasts. US-guided needle biopsy was performed in the palpable mass and in one of the multiple lesions located in the right breast. Histologic findings were compatible with a granulocytic sarcoma in both breasts, which was considered as a relapse of the AML treated a few months earlier.

Starry Sky Pattern in Hematopoietic Neoplasms: A Review of Pathophysiology and Differential Diagnosis

The starry sky pattern is a distinctive histologic feature wherein a rapidly proliferating hematolymphoid neoplasm contains scattered histiocytes with abundant pale cytoplasm in a background of monomorphic neoplastic cells. The cytoplasm of these histiocytes typically contains cellular remnants, also known as tingible bodies, incorporated through active phagocytosis. Although common and widely recognized, relatively little is known about the pathophysiological underpinnings of the starry sky pattern. Its resemblance to a similar pattern seen in the germinal centers of secondary follicles suggests a possible starting point for understanding the molecular basis of the starry sky pattern and potential routes for its exploitation for therapeutic purposes. In this review, we discuss the historical, pathophysiological, and clinical implications of the starry sky pattern.

Ultrasound Findings in a Case of Myeloid Sarcoma of the Breast

Myeloid sarcoma is a rare, solid extramedullary tumor originating from immature granulocytic cells or monocytes. Breast involvement without an aleukemic or myeloproliferative disorder is very infrequent. A 21-year-old female patient was admitted with bilateral palpable breast masses for four months. The patient had given birth approximately one year ago. The ultrasonographic examination revealed multiple, oval shaped—some of them with microlubulated margins—hypoechoic, solid masses of which, the largest mass measured 4.5 × 2.5 cm, evaluated as BI-RADS 4. The histopthological examination suggested hematolymphoid neoplasm. In the differential diagnosis of solid breast lesions, myeloid sarcoma should be kept in mind even without hematological findings. Early diagnosis of this tumor is important for the effectiveness of the medical treatment.

Granulocytic sarcoma of the breast: A case report

Granulocytic sarcoma (GS) is an unusual type of tumor composed of immature cells outside the bone marrow. The disease exhibits a correlation with acute myeloid leukemia and other myeloproliferative disorders. Although it can invade a number of areas of the body, the involvement of the breast is uncommon. The present study reports the case of a 58-year-old female with a mildly tender lump in the left breast that had been apparent for one year. Available diagnostic techniques, including ultrasound, magnetic resonance imaging and mammography, were systematically used to determine a diagnosis of GS, and lumpectomy and systemic chemotherapy were performed. The patient was satisfied with the result of no local recurrence at the one year follow-up examination. The present study discusses the clinical and pathological characteristics of the present case of GC.

Allogeneic Hematopoietic Stem Cell Transplantation as Treatment for Primary Granulocytic Sarcoma of the Breast

Primary granulocytic sarcoma (GS) is an uncommon, extramedullary proliferation of myeloid cells, occurring in the absence of antecedent myeloproliferative disorder. Breast involvement is uncommon. A diagnosis of GS portends a poor prognosis. Even with intensive chemotherapy for AML, progression to overt leukemia can be delayed for 2-3 years. We, report a 29-year-old man who presented with a painless, left breast lump. A modified radical mastectomy followed by histopathological and immunohistochemical testing confirmed a granulocytic sarcoma. There was no evidence of a concurrent leukemia. Intensive chemotherapy for acute myelogenous leukemia was instituted. Allogenic hematopoietic stem cell transplantation was successfully given. The patient remains in complete remission at follow-up. We highlight the importance of timely diagnosis of this uncommon entity with institution of intensive therapy. Early use of allogenic bone marrow transplantation in the treatment of primary GS may be warranted.

Radiotherapy for granulocytic sarcoma of the breast-Case report and review of the literature

Granulocytic sarcomas are rare tumors that can present in innumerous locations; thus there is very little clinical experience with these cases. Therefore there is no consensus on which is the best treatment for patients with this malignancy. The authors present a case of a female with a granulocytic sarcoma of the breast and review the literature for the role of radiotherapy in the management of this clinical entity.

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.

Breast leukemia: an update

BACKGROUND

Breast leukemia is extremely rare. The published data on this manifestation include predominantly case reports and do not provide any statistical information.

PURPOSE

To identify clinical signs and radiological features of breast leukemia.

MATERIAL AND METHODS

PubMed and Medline databases between 1980 and 2010 were screened using 'breast leukemia' and 'leukemia of the breast' as keywords. Secondary references were also reviewed. By this search, a total of 139 patients were identified from the literature.

RESULTS

In most patients (n = 85, 61.2%) acute myeloid leukemia was diagnosed. Acute lymphatic leukemia occurred in 35 patients (25.2%). Isolated BL before bone marrow infiltration was seen in 24 patients (17.3%). Involvement of the breast during the course of leukemia was diagnosed in 25 cases (18%). Intramammary leukemic relapse after therapy/stem cell transplantation occurred in 59 patients (42.4%). In 71 cases (51.1%) the lesions were solitary and in 57 (41%) multiple. The number of lesions was not reported in 11 patients (7.9%). There was no significant difference between the number of lesions in ML and LL. Clinically, 73% of the patients presented with palpable breast masses. Most of them were painless. Mammography was performed in 39 patients, allowing the identification of the following three mammographic patterns: breast masses (28 patients, 72%), architectural distortion (5 patients, 13%), no abnormalities (6 patients, 15%). On ultrasound, most identified masses were homogeneously hypoechoic with microlobulated or indistinct margins. On MRI, on T2-weighted images breast lesions were hyperintense. After venous administration of contrast medium, BL showed marked inhomogeneous contrast enhancement. Treatment of BL is the same as for other localizations and is based on chemotherapy and/or radiotherapy.

CONCLUSION

In the present study the clinical and radiological features of BL are described. They are non-specific. However, BL should be considered in the differential diagnosis of breast disorders, especially in patients with leukemia.

Cyto-morphological features of extramedullary acute megakaryoblastic leukemia on fine needle aspiration and cerebrospinal fluid cytology: A case report

Extramedullary deposits may be the presenting feature of acute myeloid leukemia. An early and accurate diagnosis on cytology will aid in correct patient management. This is especially true for patients with acute megakaryoblastic leukemia (AML M7), where bone marrow aspiration may yield only a dry tap. While cytomorphological features of myeloid sarcoma of other types are well recognized due to its rarity, there are only two case reports discussing the morphological details of megakaryoblastic differentiation on aspiration cytology. We present the case of a 25-year-old patient with extramedullary involvement of lymph node and cerebrospinal fluid by AML M7, describing in detail, the morphological features on aspiration as well as exfoliative cytology.

FDG PET/CT manifestations of hematopoietic malignancies of the breast

Hematopoietic malignancies that can be encountered in the breast include lymphoma, leukemia, and multiple myeloma/plasmacytoma. These are readily imaged via [18]F-fluorodeoxyglucose position emission tomography (PET)/computed tomography (CT) and can manifest as unilateral, bilateral, single, multiple, round/oval masses, or diffuse. These malignancies can occasionally mimic primary breast cancers. Conversely, benign conditions, such as the lactating breast can resemble hematopoietic malignancies of the breast. Although uncommon, familiarity with hematopoietic malignancies of the breast is important for proper interpretation of PET/CT. In this pictorial review, the PET/CT imaging features of patients with hematopoietic malignancies of the breast will be described, including pathology-proven cases of acute myelogenous leukemia, diffuse B-cell lymphoma, follicular lymphoma, acute myeloid leukemia with neutropenic granulocytic) sarcoma, and plasmacytoma. In addition, potential pitfalls will be discussed.

PAX-5: a valuable immunohistochemical marker in the differential diagnosis of lymphoid neoplasms

OBJECTIVE

Undifferentiated tumors and hematolymphoid neoplasms can be diagnostically challenging due to potential overlap of morphologic features and variant antigen expression. PAX-5, a transcription factor expressed throughout B-cell maturation, is detected in most B-cell neoplasms including those that lack expression of mature B-cell markers, such as classical Hodgkin lymphoma (cHL), B-lymphoblastic leukemia and B-cell lymphomas following rituximab therapy. The lack of PAX-5 expression in most CD30-positive non-hematopoietic malignancies (embryonal carcinoma and seminoma) and T-cell lymphomas, such as anaplastic large cell lymphoma (ALCL), suggests that the absence of PAX-5 may be used to confirm non-B-cell lineage. The goal of this study was to retrospectively assess PAX-5 immunoreactivity in diagnostic samples of hematolymphoid and other non-hematopoietic malignancies.

DESIGN

Diagnostic lymph node, decalcified core bone marrow biopsies and tissue sections from 111 archived paraffin-embedded tissue blocks and a tissue lymphoma microarray were immunostained using a monoclonal antibody to PAX-5. The corresponding hematoxylin and eosin stained tissue sections and additional immunostains were simultaneously evaluated. PAX-5 immunoreactivity in neoplastic cells was scored as positive or negative. This study was exempted by the Institutional Review Board for Human Research.

RESULTS

Nuclear PAX-5 immunoreactivity was detected in 88% (36/41) of Hodgkin lymphoma, all cases of diffuse large B-cell lymphoma (n=72), small B-cell lymphomas (n=5), B-lymphoblastic leukemia/lymphoma and mixed phenotype acute leukemia with B-cell lineage (n=5). PAX-5 was not detected in ALCL (n=22), T-cell lymphoblastic leukemia/lymphoma, mixed phenotype acute leukemia with T-cell lineage (n=5), acute myeloid leukemia (n=4), carcinoid tumors with typical morphology (n=5), melanoma (n=3), and undifferentiated/metastatic tumors (n=8). Non-neoplastic bone marrow sections showed scattered nuclear staining in small B-cell lymphocytes/hematogones. The detection of PAX-5 immunoreactivity resulted in the reclassification of two cases of ALCL to cHL.

CONCLUSION

Overall, our results demonstrate that including PAX-5 in a panel with other immunomarkers helps establish B-cell lineage and increases diagnostic yield.

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.

Diagnosis of myeloid sarcoma involving salivary glands by fine-needle aspiration cytology and flow cytometry: report of four cases

Myeloid sarcoma involving salivary glands is extremely rare. Here, we report four cases of this rare occurrence, diagnosed by fine-needle aspiration biopsy. All of four patients had previous diagnoses of myeloid neoplasms. They presented with a solitary mass in the parotid or submandibular salivary gland. The cytological evaluation of the aspirates revealed scattered salivary gland acini admixed with dispersed atypical cells. In three cases, the atypical cells appeared to be heterogeneous, intermediate to large in size, and have folded nuclei with fine chromatin. In another case the atypical cells were monotonous and had round nuclei with fine chromatin. The myeloid lineage of the atypical cells was demonstrated by flow cytometric analysis. High clinical suspicion, careful cytological evaluation, and concurrent ancillary studies are essential for establishing a diagnosis of myeloid sarcoma.

Granulocytic sarcoma - a rare presentation of a breast lump

This report describes a woman who presented with a breast lump, which was initially misdiagnosed as lymphoma, but later turned out to be granulocytic sarcoma of the breast.

Myeloid sarcomas: a histologic, immunohistochemical, and cytogenetic study

Context. -

Myeloid sarcoma (MS) is a neoplasm of immature granulocytes, monocytes, or both involving any extramedullary site. The correct diagnosis of MS is important for adequate therapy, which is often delayed because of a high misdiagnosis rate.

Objective. -

To evaluate the lineage differentiation of neoplastic cells in MS by immunohistochemistry, and to correlate the results with clinicopathologic findings and cytogenetic studies.

Design. -

Histologic and immunohistochemical examinations were performed on formalin-fixed paraffin-embedded tissue samples from 13 cases of MS. They were classified according to the World Health Organization criteria. Chromosomal analysis data were available in 11 cases. Clinical, pathological, and cytogenetic findings were analyzed.

Results. -

The study included six male and seven female patients with an age range of 25 to 72 years (mean, 49.3 years) and a male to female ratio of 1:1.2. MS de novo occurred in 4/13 (31%) of cases examined. The most sensitive immunohistochemical markers were CD43 and lysozyme present in all cases with MS (13/13, 100%). All de novo MS showed a normal karyotype, monoblastic differentiation, and lack of CD34. The most common chromosomal abnormalities in MS associated with a hematopoietic disorder were trisomy 8 and inv(16) (2/11, 18%).

Conclusion. -

An immunohistochemical panel including CD43, lysozyme, myeloperoxidase (MPO), CD68 (or CD163), CD117, CD3 and CD20 can successfully identify the vast majority of MS variants in formalin-fixed paraffin-embedded tissue sections. The present report expands the spectrum of our knowledge showing that de novo MS has frequent monoblastic differentiation and frequently carries a normal karyotype.

Diagnostic uses of Pax5 immunohistochemistry

Pax5, or B-cell-specific activator protein, is a nuclear protein in the paired-box containing (PAX) family of transcription factors involved in control of organ development and tissue differentiation. Pax5 is mostly expressed in B lymphocytes and B-cell lymphomas, although recent data have shown expression in the developing central nervous system, some neuroendocrine tumors, and occasional myeloid leukemias. Pax5 immunohistochemistry shows robust nuclear staining, and has become a valuable tool in the diagnosis and subclassification of lymphomas. Pax5 staining is positive in most Hodgkin and B-cell non-Hodgkin lymphomas, and also precursor B-cell lymphoblastic neoplasms. Plasma cell neoplasms, multiple myeloma, and plasmablastic lymphomas typically are negative. T-cell lymphomas are, to date, consistently negative. Recently, Pax5 expression has been described in the majority of small cell carcinomas and Merkel cell carcinomas. Rare cases of Pax5 expression in other carcinomas have been reported. With these exceptions, Pax5 immunohistochemistry is fairly specific for B-cell lineage and is a valuable addition to the armamentarium of markers available for lymphoma subtyping.

Ectopic expression of PAX5 promotes maintenance of biphenotypic myeloid progenitors coexpressing myeloid and B-cell lineage-associated genes

The transcription factor PAX5 is a critical regulator of B-cell commitment and development. Although normally not expressed in myeloid progenitors, PAX5 has recently been shown to be frequently expressed in myeloid malignancies and to suppress expression of myeloid differentiation genes, compatible with an effect on the differentiation or maintenance of myeloid progenitors. However, previous studies in which PAX5 was ectopically expressed in normal myeloid progenitors in vivo and in vitro provided conflicting results as to the effect of PAX5 on myeloid development. Herein, we demonstrate that on ectopic expression of PAX5 in bone marrow multipotent stem/progenitor cells, cells with a biphenotypic B220+GR-1/MAC-1+ phenotype are produced. These remain cytokine-dependent, but unlike control-transduced cells they sustain long-term generation of myeloid progenitors in vitro and remain capable of myeloid differentiation. Notably, PAX5+B220+GR-1/MAC-1+ myeloid progenitors coexpress, at the single-cell level, myeloid genes and otherwise B-cell–specific PAX5 target genes. These findings establish that ectopic expression of PAX5 introduces extensive self-renewal properties in otherwise short-lived myeloid progenitors. Along with the established ectopic expression of PAX5 in acute myeloid leukemia, this motivates a careful investigation of the potential involvement of ectopic PAX5 expression in myeloid and biphenotypic leukemias.

Myeloid sarcoma of the urinary bladder and epididymis as a primary manifestation of acute myeloid leukemia with inv(16)

Myeloid sarcoma (MS) of the lower urinary tract is rare. We describe a 47-year-old man with hematuria, who was subsequently found to have MS involving bladder and epididymis. The neoplasm was composed predominantly of blasts that expressed CD68, CD117, myeloperoxidase, and lysozyme, with occasional immature eosinophils. Although blood and bone marrow examinations showed no morphologic evidence of leukemia, conventional cytogenetic studies of marrow demonstrated inv(16)(p13q22) in 4 of 20 metaphases; fluorescence in situ hybridization of the bladder neoplasm also showed inv(16). Following chemotherapy, the patient has been in complete remission for 32 months. In our literature review, we identified 7 cases of MS involving bladder, only 3 without evidence of an associated myeloid neoplasm in marrow, none with cytogenetic data. A high index of suspicion is required to establish the diagnosis of MS involving bladder. Cytogenetic analysis is useful for both demonstrating minimal marrow disease and classifying MS in paraffin-embedded tissue sections.

Myeloid sarcoma of appendix mimicking acute appendicitis

CONTEXT

Myeloid sarcoma is a neoplasm of immature myeloid cells involving an extramedullary anatomic site that is usually, although not always, associated with acute myeloid leukemia. Any extramedullary site can be involved by myeloid sarcoma, but involvement of the cecal appendix is uncommon, and symptoms mimicking acute appendicitis as a result of appendiceal involvement are rare.

OBJECTIVE

To describe the clinicopathologic features of 2 patients with myeloid sarcoma involving the appendix who presented with right lower quadrant pain suggestive of acute appendicitis and prompting appendectomy.

DESIGN

Clinical information for both patients was obtained from the medical record. Routine hematoxylin-eosin-stained slides, naphthol-ASD-chloroacetate stain, and immunohistochemical stains for myeloid, B-cell, and T-cell antigens were prepared.

RESULTS

Peripheral blood and bone marrow were infiltrated by coexistent acute myeloid leukemia in case 1 but were negative for leukemia in case 2. In case 2, the patient had a history of acute myeloid leukemia that had been treated by an allogenic bone marrow transplant 7 months earlier. Histologic examination of the appendix revealed poorly differentiated myeloid sarcoma in both cases. Each neoplasm was positive for chloroacetate esterase, myeloperoxidase, lysozyme, and CD43 and was negative for CD3 and CD20.

CONCLUSIONS

Myeloid sarcoma involving the appendix can rarely cause pain or other symptoms mimicking acute appendicitis. A high index of suspicion combined with the use of cytochemical and immunohistochemical studies are helpful in establishing the diagnosis.