Mycobacterial spindle cell pseudotumor of lymph nodes

Histologic Features of Mycobacterial Spindle Cell Pseudotumors: A Multi-institutional Clinicopathologic Analysis of 14 Cases

Mycobacterial spindle cell pseudotumors (MSPs) are a rare and diagnostically challenging manifestation of non-tuberculous mycobacterial (NTM) infections. Proper recognition of these pseudotumors is important because they are treatable and benign. In this study, we evaluated the morphologic patterns of MSPs to improve their pathologic identification. Clinical and morphologic features of 14 MSPs were analyzed. Histologic factors evaluated included the architectural growth pattern of spindled or epithelioid macrophages, granulomas and their location within the lesion, neutrophilic microabscesses, multinucleated giant cells, necrosis, and effacement of background tissue. The composition of inflammatory infiltrates, organism density by acid-fast staining, and stromal changes were also assessed. In addition, 8 of 14 cases underwent molecular microbiology identification by a clinical amplicon-sequencing assay for non-tuberculous mycobacteria. MSP sites included 2 bowel, 10 lymph nodes, 1 liver, and 1 extremity. Cases with available clinical history (n=10) all occurred in immunocompromised patients. All demonstrated effacement of normal structures with spindled cells arranged in a storiform or fascicular architectural pattern. In addition, all cases showed lymphocytic inflammation, with prominent concurrent neutrophilic inflammation in 50% (7/14) of cases. Other morphologic findings included foamy histiocytes (64%, 9/14), peripherally situated granulomas (21%, 3/14), and neutrophilic microabscesses (21%, 3/14). All tested cases were positive for NTM by PCR methods. Mycobacterium avium was the most commonly isolated pathogen (6/8). Mycobacterial spindle cell pseudotumors show predominantly spindled morphology that may be mistaken as a neoplasm. Surgical pathologists who evaluate lymph nodes, soft tissue, and gastrointestinal tissues should be aware of this spindled tumefactive phenomenon in the setting of immunocompromised patients. Recognition of key morphologic features of neutrophilic inflammation, peripheral granulomas, or foamy histiocytes within a spindled lesion can help guide the pathologist to a correct diagnosis of an inflammatory process secondary to infection rather than a spindle cell neoplasm. Accurate diagnosis to facilitate appropriate antimicrobial and/or surgical therapy requires a comprehensive evaluation combining clinical, histopathologic, and microbiological findings.

Mycobacterial Spindle Cell Pseudotumor of the Nasal Cavity

BACKGROUND

Mycobacterial spindle cell pseudotumor (MSCP) represents an uncommon tumor-like proliferation associated with nontuberculous mycobacterial infection, i.e., M. avium intracellulare, affecting primarily the lymph nodes of immunocompromised men in their 5th decade. Involvement of the nasal cavity by MSCP is exceedingly rare with only 3 well-documented examples in the literature.

METHODS

A 74-year-old, HIV-negative, man presented with a 0.5-cm nodule of the left nasal cavity clinically presenting as a "nasal polyp." His medical history was significant for colonic adenocarcinoma, cutaneous basal cell carcinoma, and chronic lymphocytic leukemia (CLL) transforming to B-cell prolymphocytic leukemia, responsive to chemotherapy. The patient was diagnosed with prostatic adenocarcinoma treated with radiotherapy two months before the nasal lesion was detected. No lymph node enlargement, pulmonary involvement or hepatosplenomegaly were noticed. The nasal nodule was surgically excised and histopathologically examined to rule out metastatic disease or CLL relapse.

RESULTS

Microscopically, the lesion comprised a well-circumscribed, monotonous, spindle cell population in a vaguely storiform arrangement mixed with a heavy infiltrate of neutrophils and sparse lymphocytes. The spindle cells featured finely granular rich eosinophilic cytoplasm with rounded, oval to epithelioid, or elongated nuclei with vesicular chromatin and one or two distinct nucleoli. The lesional cells lacked overt cytologic atypia and showed occasional regular mitoses. The surface epithelium was intact or focally ulcerated. By immunohistochemistry, the spindle cell population stained strongly and diffusely for CD68 and was negative for AE1/AE3, SMA, CD34, and PSA. CD3 highlighted scattered lymphocytes. Ziehl-Neelsen stain disclosed numerous intracytoplasmic acid-fast bacilli. A diagnosis of MSCP was rendered. No recurrences were observed during a 24-month follow-up period.

CONCLUSION

Although exceptionally rare, MSCP should be considered in the differential diagnosis of nodular lesions of the nasal cavity that are characterized microscopically by marked spindle cell proliferation in a vague storiform pattern, admixed with a lymphocytic or mixed inflammatory infiltrate. A negative medical history for HIV infection and medication-induced immunosuppression should not preclude a diagnosis of MSCP, particularly in extranodal sites. Once the diagnosis is established, prognosis appears to be excellent for nasal MSCP following conservative surgical excision.

Diagnosis of cutaneous mycobacterial spindle cell pseudotumor in the absence of typical inflammatory cells: A case report

Mycobacterial spindle cell pseudotumor (MSP) is a non-neoplastic condition that is characterized by spindle-shaped histiocytes colonized by mycobacteria. MSP is most commonly diagnosed in the immunocompromised and, while MSP can occur throughout the body, the most common sites of MSP involvement are the lymph nodes and the skin. To diagnose MSP, histopathological analysis typically demonstrates the presence of inflammatory cells, in addition to spindle cells and the unequivocal mycobacteria, which guides the diagnosis away from potential neoplasms. If properly diagnosed and treated with appropriate antibiotic therapy, patients tend to experience almost complete resolution of their symptoms. MSP is a rare condition; to our knowledge, there have only been 11 documented cases of cutaneous MSP, including the one introduced in this report. Here, we present a unique case of a 50-year-old female on chronic immunosuppressive therapy diagnosed with cutaneous MSP in the absence of inflammatory cells on pathology.

Mycobacterial spindle cell pseudotumor in a woman with HIV

Mycobacterial spindle cell pseudotumor (MSP) is a rare benign entity characterized by tumor-like proliferations of spindle-shaped histiocytes containing acid-fast positive mycobacteria. MSPs tend to occur predominantly in immunocompromised individuals and are concerning for a malignant neoplasm. We report a case of MSP occurring in a woman with human immunodeficiency virus and a tumor-like mass in the abdomen. A subsequent biopsy revealed MSP, which was successfully treated with antimycobacterial therapy.

Pulmonary Mycobacterium Spindle Cell Pseudotumor in Patient With Liver Transplant

We report a case of liver transplant patient who presented with lung masses, found to be Mycobacterium spindle cell pseudotumors. The masses demonstrated hypermetabolic activities on positron emission tomography. Core biopsy revealed sheets of spindle histiocytic cells with abundant acid-fast bacilli identified as Mycobacterium avium-intracellulare complex. This finding is a rare presentation of Mycobacterium infection, mainly nontuberculous Mycobaterium. It is characterized by a benign, spindle cell mass-forming reaction. Most of the reported cases had acquired immune deficiency syndrome or organ transplant. Histopathology illustrating the proliferation of spindle cell shaped histiocytes containing numerous acid-fast bacilli is the gold standard for diagnosis. The standard treatment has not been well established; previously reported cases followed the standard treatment for Mycobacterium based on organ involvement. Our case is the first case to our knowledge that reports pulmonary Mycobacterium spindle cell pseudotumors in a liver transplant recipient.

Diagnostic histochemistry of soft tissue lesions

Histochemical methods (HM) were, at one time, extensively used in all facets of anatomic pathology, including analysis of soft tissue lesions. That situation has changed with the advent of other adjunctive procedures, but HM still do contribute meaningfully to the evaluation of several tumefactive conditions in the soft tissue. This brief review considers selected neoplastic, quasineoplastic, and pseudoneoplastic lesions in that category, with emphasis on their histochemical properties.

Mycobacterial spindle cell pseudotumour: epidemiology and clinical outcomes

INTRODUCTION

Mycobacterial spindle cell pseudotumour (MSP) is a rare disease characterised by tumour-like local proliferation of spindle-shaped histiocytes containing acid-fast positive mycobacteria. The aim of this literature review is to describe the clinical parameters and treatment outcomes of patients with MSP.

METHODS

A literature search was conducted using the search terms related to mycobacteria and spindle cell tumours. A previously unreported stem cell transplant recipient from our institution diagnosed with MSP was also included. Demographics, comorbidities, site of infection, treatment and clinical outcomes were analysed.

RESULTS

Fifty-one patients were analysed. Twenty-six (51%) had HIV infection. Mycobacterium avium complex was the most frequent organism isolated in 24 (47.1%) followed by Mycobacterium tuberculosis complex in eight (16%) cases. Lymph nodes were the most common site of infection (45.1%). Twenty (39.2%) patients received antimycobacterial agents, 12 (23.5%) underwent surgical resection and six (11.8%) received antimycobacterial agents plus surgery. Treatment was successful in 24 (47.1%) patients and failed in 15 (29.4%); 13 of these 15 patients died. Antimycobacterial therapy was significantly associated with successful outcome compared with surgical resection or no treatment (P<0.001).

CONCLUSION

MSP is a rare condition associated primarily with immunodeficiencies. Antimycobacterial therapy is significantly associated with successful outcome.

A pattern-based approach to reactive lymphadenopathies

A crucial task in histopathological examination of enlarged lymph nodes is to discriminate malignant form benign processes. The central importance of this issue is reflected by the fact that benign lymphadenopathies mistaken for lymphomas belong to the most commonly misdiagnosed cancers. In addition, recognition of distinct histopathological patterns of reactive lymph node changes narrow down the potential number of causative agents, especially of those that can be specifically identified by means of often very resource-consuming ancillary techniques; thus, the more precise the differential diagnosis established upon histopathological examination is, the more targetable and efficient the application of these techniques will be. This review provides a synopsis on a histopathological pattern-based approach towards reactive lymphadenopathies.

Inflammatory Pseudotumor of the Mediastinum Associated With Azacytidine Therapy, Acute Myeloid Leukemia, and Previous Chemotherapy for Astrocytoma

We report the rare case of a rapidly growing inflammatory pseudotumor arising in the mediastinum of a 30-year-old man with myelodysplastic syndrome secondary to treatment for grade 3 astrocytoma. The tumor was discovered soon after discontinuation of 5-azacytidine therapy for myelodysplasia. Fine-needle aspiration was suggestive, and thoracoscopic biopsy was diagnostic. The tumor was excised because of rapid growth and encroachment on the left pulmonary artery and lung. Postoperatively, blastemia was discovered. Acute myeloid leukemia was confirmed by bone marrow biopsy. The patient died of aspiration pneumonia before commencement of leukemia chemotherapy. This case illustrates a rare occurrence of inflammatory pseudotumor in the mediastinum complicating or arising in the setting of multiple primary cancers and chemotherapy. A temporal association with azacytidine therapy is noted. Int J Surg Pathol 3(1):49-58, 1995

Mycobacterial spindle cell pseudotumour of the brain in a patient with sarcoidosis

Mycobacterial spindle cell pseudotumours (MSP) are benign lesions characterised by local proliferation of spindle-shaped histiocytes caused by mycobacterial infections. Cerebral MSP due to Mycobacterium avium intracellulare (MAI) infection is rare, and is often misdiagnosed clinically and radiologically as a brain tumour. We present a case with underlying sarcoidosis and known pulmonary MAI infection presenting with partial seizures and headaches. Imaging of the brain revealed a solitary extra axial tumour within the right temporal area. Biopsy of the tumour showed evidence of MPS due to MAI infection. Prolonged treatment with antituberculous therapy showed complete resolution of the cerebral lesion.

Nontuberculous mycobacteria-associated spindle cell pseudotumor of the nasal cavity: a case report

Mycobacterial spindle cell pseudotumor (MSP) is a rare mass-forming lesion caused by mycobacterial infection, mostly in immunocompromised patients. Since it is composed of a proliferation of spindle-shaped fibrohistiocytic cells without forming epithelioid cell granulomas, histological distinction from other spindle cell lesions is often difficult and its pathophysiology is poorly understood. MSP arising in the nasal cavity is extremely rare, and only two cases have been reported previously. Here we report a case of MSP of the nasal cavity in an 83-year-old man with no evidence of immunodeficient state. The resected tumor consisted of spindle cells, which contained numerous acid-fast bacilli in the cytoplasm. By polymerase chain reaction and sequencing using DNA extracted from the paraffin sections, the bacilli were identified as Mycobacterium intracellulare. Immunohistochemistry revealed that the spindle cells were positive for CD68, CD11c and S100 protein, confirming the histiocytic nature of these cells. They were also positive for CD163 and CD204, suggesting that they showed a phenotype similar to alternatively activated (M2) macrophages and the phenotype might contribute to the maintenance of mycobacterial infection despite apparent immunocompetence of the host.

HIV/AIDS Related Respiratory Diseases

Lungs are the most commonly involved organ by HIV/AIDS related diseases, and pulmonary infections are the main reasons for the increasing death rate from AIDS. Pathogens of HIV related pulmonary infections include parasites, fungi, mycobacteria, viruses, bacteria and toxoplasma gondii. According to international reports, pathogens have different geographical distribution, which is also closely related to the socioeconomic status of the region to produce varied AIDS related diseases spectra. For instance, in the United States, pneumocystis carnii pneumonia (PCP), tuberculosis and recurrent bacterial pneumonia (at least twice within 1 year) occur frequently in HIV infected patients. An international report published 10 years ago indicated that PCP is the most common and serious pulmonary opportunistic infections in HIV infected patients. Now its incidence has dropped with the application of antiretroviral treatment and preventive measures. PCP will continue to occur initially in patients who are aware of their HIV infection. In addition, HIV related viral and parasitic infections have been reported both domestically and internationally. In this section, the clinical manifestations and imaging findings of HIV related pulmonary infections are analyzed and discussed, which provide effective diagnosis basis, so as to reduce the incidence of HIV-related pulmonary infections.

Pulmonary histoplasmosis producing a spindle cell "pseudotumor"

Pulmonary spindle cell proliferations have been reported in association with a limited group of infectious agents. These lesions are rare and identified most often in the setting of immunosuppression. Because their appearance can simulate a spindle cell neoplasm, they are diagnostically treacherous, sometimes delaying antimicrobial therapy or resulting in unnecessary surgery. We report a case of a spindle pseudotumor of the lung resulting from Histoplasma capsulatum infection, a previously unreported cause of a spindle cell lesion in the lung. The patient was a 67-year-old woman in whom positron emission tomography-positive nodules developed in the left lung and left mediastinum. The patient had undergone renal transplantation and was receiving immunosuppressive therapy with mycophenolate, tacrolimus, and low-dose prednisone. Infection with H capsulatum was confirmed by culture of pleural effusion fluid, DNA probe analysis of the pleural fluid culture isolate, urinary Histoplasma antigen detection, and Grocott methenamine silver stains of tissue sections. To our knowledge, this is the first case of a spindle cell "pseudotumor" of the lung resulting from histoplasmosis. It highlights the importance of performing special stains for organisms when evaluating pulmonary spindle cell lesions in an immunocompromised host.

Primary schwannoma in a cervical lymph node

BACKGROUND

Spindle cell neoplasms within lymph nodes are rare and include benign and malignant tumors and primary and metastatic tumors such as palisaded myofibroblastoma, leiomyoma, leiomyosarcoma, reticular cell neoplasms, and vascular sarcomas. Ancillary studies may help distinguish these neoplasms.

METHODS

A 77-year-old white woman was seen with a painless, slowly growing mass of the left neck. Her clinical history was noncontributory. An excisional biopsy was performed without complication. There has been no recurrence, to date, of the lesion.

RESULTS

Gross examination, microscopic examination, immunohistochemistry, and ultrastructural studies were consistent with the diagnosis of schwannoma arising within a lymph node.

CONCLUSIONS

We report the first case of intranodal schwannoma arising in a cervical lymph node. The recognition of intranodal schwannoma is important because it is cured with excision, whereas some of the other diagnostic considerations for a spindle cell lesion within a lymph node may require radiation or chemotherapy.

Mycobacterium microti infection associated with spindle cell pseudotumour and hypercalcaemia: a possible link with an infected alpaca

A 44-year-old woman who had recently been on immunosuppressive therapy presented with malaise, cough, fever, weight loss, lymphadenopathy, severe hypercalcaemia and a paratracheal mass on imaging. The initial impression was of disseminated malignancy, and lymphoma was suspected. A mediastinal biopsy showed a mycobacterial spindle cell pseudotumour containing acid and alcohol fast bacilli (AAFB). Sputum microscopy demonstrated AAFBs, confirmed as Mycobacterium tuberculosis complex by PCR. Prolonged culture grew Mycobacterium microti, an organism often associated with disease in small rodents and llamas. M microti isolates from postmortem samples of an alpaca at a nearby farm were genetically indistinguishable. Although the patient had not visited the farm, concurrent illness in her adopted stray cat suggested a possible zoonotic connection. The patient responded to antituberculous therapy, and rehydration and pamidronate for hypercalcaemia. We believe the hypercalcaemia was caused by a similar mechanism to raised calcium levels sometimes seen in tuberculosis.

Pseudoneoplastic lesions: general considerations

Pseudoneoplastic lesions ("pseudotumors") can be seen in virtually all anatomic locations. Some organ sites, such as the lungs and skin, are overrepresented for unknown reasons, and the histologic images seen in pseudoneoplastic lesions are partially overlapping in disparate locations. More than occasionally, the degree of histologic likeness to true neoplasms-often malignant ones-is striking. This overview outlines the spectrum of pseudoneoplastic lesions and divides them into etiologic categories, including reparative, developmental, functional (usually endocrine), iatrogenic, infectious, and idiopathic. Side-by-side pictorial comparisons of selected pseudoneoplastic lesions and their neoplastic mimics are included.

Nodal inflammatory pseudotumor caused by luetic infection

Inflammatory pseudotumor of lymph nodes (IPT-LN) represents an unusual cause of lymphadenitis of unknown etiology. Upon the observation of a case of IPT-LN associated with Treponema pallidum (Tp) infection, we analyzed a series of 9 IPT-LN and 9 extranodal IPT (spleen, 4 cases; lung, orbit, gut, skin, and liver) for the presence of Tp, using a polyclonal antibody anti-Tp. At the time of biopsy, none of the patients was suspected for luetic infection, nor specific serologic tests were available. IPT-LN areas extensively involved the nodal parenchyma in 4 cases, whereas they were focal in the remaining 5 cases. Capsular thickening and inflammation (6/9), venulitis (3/9), small granulomas (3/9), and follicular hyperplasia (7/9) were observed in the associated lymphoid parenchyma. Tp were detected in 4/9 cases of LN-IPT and in none of the extranodal IPT. Tp were extremely abundant within the IPT areas and in the perivascular tissues in the surrounding parenchyma, whereas they were scattered within the capsule. In Tp+ cases, marked follicular hyperplasia was the single distinctively associated feature. Double immunostains revealed that Tp were predominantly contained in the cytoplasm of CD11c+ CD163+ macrophages, some of which co-expressed HLA-DR. In addition, scattered S100+ interdigitating dendritic cells also showed intracytoplasmic Tp. This study shows that a significant number of IPT-LN is associated with Tp infection. A spirochetal etiology can be suspected in cases of IPT-LN, independently from the extension of the lesions, especially when pronounced follicular hyperplasia is found. Infection by Tp of macrophages and dendritic cells are in keeping with in vitro data and indicate that immune mediated mechanisms may be involved in the pathogenesis of the lesions.

Cryptococcal Inflammatory Pseudotumors

"Inflammatory pseudotumors" (IPTs) embrace a heterogeneous spectrum of reactive, infective, and neoplastic entities, that are characterized by a clinical mass composed of a histologic proliferation of spindle cells in a background of inflammatory cells and collagen fibers. Although a spectrum of microorganisms have been identified in infective IPTs, mycobacterial infective IPTs are reported most commonly. We document 5 solitary cryptococcal IPTs, in 2 males and 3 females, aged 19 to 43 years, in the soft tissues of the anterior chest wall, thigh, and arm. All were HIV-positive and had been treated for disseminated cutaneous and/or meningeal cryptococcosis with antifungal therapy, 6 to 12 months earlier. The specimens demonstrated a storiform arrangement of plump spindle cells, in addition to spindle and polygonal cells that were arranged in a haphazard manner. Background lymphocytes, plasma cells, and fibrosis were noted, in addition to scattered giant cells and focal necrosis. On high-power examination, Cryptococcus neoformans yeasts were identified within and between vacuolated spindle and polygonal cells on routine and special stains, confirming cryptococcal IPTs. Immunophenotyping of the spindle cells confirmed a mixed histiocytic and myofibroblastic lineage, with a predominance of the former. In documenting 5, hitherto unreported, pseudotumoral spindle cell reactions to C. neoformans, we not only highlight the need for intense appraisal of all IPTs for infective agents on routine and special stains and investigations, but also postulate that a complex host-fungus interaction, coupled with an exuberant, myofibroblastic response to incomplete therapy, are the pathogenetic drive for the pseudotumoral presentation.

The morphological spectrum of lymphadenopathy in HIV infected patients

AIMS

To study the histological spectrum of lymphadenopathy in human immunodeficiency virus (HIV) infected Thai patients.

METHODS

Lymph nodes from 55 HIV infected patients were accessioned over a 19 month period in two pathology laboratories in Bangkok, Thailand. These were examined with H&E, Ziehl-Neelsen, periodic acid-Schiff (PAS), PAS with diastase (PAS/D), Gram and methenamine stains.

RESULTS

Six reaction patterns were observed: (1) classic necrotising granulomas (30 cases); (2) extensive necrosis with minimal granulomatous response (5 cases); (3) sarcoid-like non-necrotising granulomas (5 cases); (4) foamy macrophage or pseudo-Gaucher cell response (5 cases); (5) inflammatory pseudotumour-like proliferation (3 cases); and (6) non-specific lymphoid hyperplasia (7 cases). Myriads of intracellular, long, slender acid-fast bacilli were found in those cases with the pseudo-Gaucher cell and inflammatory pseudotumour-like response, while variable numbers of bacilli were identified in those cases with non-necrotising sarcoid-like granulomas. Few scattered acid-fast bacilli were found in five cases with necrotising granulomas. In one case, yeast-like organisms in keeping with Cryptococcus were identified. No organisms were identified in the cases showing lymphoid hyperplasia, extensive necrosis and minimal granulomatous response, and in the remaining cases of classic necrotising granulomas.

CONCLUSIONS

The wide spectrum of histological changes in HIV-associated lymphadenomegaly requires recognition, particularly as the majority were associated with acid-fast organisms, mostly in keeping with the morphological features of Mycobacterium avium-M. intracellulare complex that was distinctively stained by Grocott methenamine-silver, Gram and PAS stains. The histological changes mimic those of infarction and other infective lymphadenitis, sarcoidosis, Whipple's disease, inflammatory pseudotumour and spindle cell neoplasms.

Follicular localization of dendritic cells in a xanthomatous inflammatory tumor of lung associated with human herpes virus-8 infection

A 17-year-old man was treated with chemotherapy and radiation for nodular sclerosing Hodgkin lymphoma that presented as a left chest wall mass. Ten years later, a left upper lobe lung tumor was identified. The tumor resection demonstrated a 1.3-cm yellow lung nodule composed of epithelioid and spindled lipid-laden CD68+ and Factor XIIIa+ macrophages. Distinct follicular structures with dendritic cells positive for CD1a, fascin, and ALK-1 and largely devoid of intracytoplasmic lipid were a distinguishing feature of the lesion. Most of the xanthomatous macrophages expressed human herpes virus-8 antigen. The current World Health Organization classification of "inflammatory myofibroblastic tumors" is examined, and the association of a subset of "inflammatory pseudotumors" with immunodeficiency states and opportunistic infection is discussed.

When typical is atypical: mycobacterial infection mimicking cutaneous vasculitis

Patients with systemic lupus erythematosus (SLE) who present with skin disease pose the clinician with diagnostic challenges. The skin disease can reflect an increase in systemic disease activity suggested by other features of active lupus and, as such, usually responds well to more aggressive immunosuppressive therapy. Other possibilities of skin disease include drug eruptions, skin disease unrelated to SLE and, more rarely, opportunistic skin infection. In patients who show a poor response to more aggressive immunosuppressive therapy, consideration must be given to the possibility of opportunistic infection. A high index of suspicion will allow prompt treatment. We describe two patients with SLE who developed cutaneous atypical mycobacterial infection during immunosuppressive therapy. The diagnosis of cutaneous vasculitis was considered in both cases, but subsequent skin biopsy revealed the correct diagnosis. This report illustrates the importance of skin biopsy in patients with suspected cutaneous lupus who are not responding to immunosuppressive therapy.

Fine-needle aspiration diagnosis of Kaposi's sarcoma in a developing country

Fine-needle aspiration (FNA) cytology was performed on 15 patients with peripheral lymphadenopathy and/or skin lesions referred to the Department of Pathology of the Hospital Central of Maputo, Maputo, Mozambique. Epitrochlear lymph nodes were the most frequently aspirated site. All aspirates allowed diagnoses of Kaposi's sarcoma (KS). Smears contained loosely cohesive clusters of bland spindle cells, with a radial arrangement and nuclear crush artifacts. These diagnostic clues have not been described in other spindle-cell intranodal lesions that should be considered in differential diagnoses. Taking into consideration the high prevalence of AIDS and limited resources for diagnosis in Africa, FNA cytology appears to be a useful method for the diagnosis of KS in developing countries, reducing the necessity for surgical lymph node excision.

Inflammatory pseudotumor causing small bowel obstruction and mimicking lymphoma in a patient with AIDS: clinical improvement after initiation of thalidomide treatment

A patient with AIDS was diagnosed with inflammatory pseudotumor with small bowel involvement. After receiving thalidomide treatment, serum tumor necrosis factor (TNF) and soluble TNF receptor II levels normalized, his constitutional and gastrointestinal symptoms diminished, and the mass lesion shrunk.

Mycobacterial spindle cell pseudotumor of the brain: a case report and review of the literature

Spindle cell pseudotumors found in the skin, lymph nodes, bone marrow, spleen, lungs, and retroperitoneum have been reported recently in immunosuppressed patients, including those with acquired immunodeficiency syndrome. The authors report a similar lesion limited to the brain in a 38-year-old human immunodeficiency virus-negative man receiving steroid therapy for treatment of sarcoidosis. Histopathologically the lesions were composed of spindle and epithelioid histiocytes, small foci of necrosis, and numerous acid-fast bacilli. The acid-fast bacilli were determined by culture and polymerase chain reaction to be Mycobacterium avium intracellulare. Because of the uncommon histologic appearance of this lesion and the potential for treatment if recognized, mycobacterial spindle cell pseudotumors should be included in the differential diagnosis of spindle cell lesions in the brain in immunosuppressed patients.

Spindle cell tumors associated with mycobacteria in lymph nodes of HIV-positive patients: 'Kaposi sarcoma with mycobacteria' and 'mycobacterial pseudotumor'

Patients infected with HIV often have unusual manifestations of common infections and neoplasms. One such example is "mycobacterial pseudotumor," an exuberant spindle cell lesion induced in lymph nodes by mycobacteria. Kaposi sarcoma also produces a spindle cell proliferation in lymph nodes of HIV-positive patients. These two entities must be differentiated from one another because of differences in treatment and prognosis. We report here, however, three cases of intranodal Kaposi sarcoma with simultaneous mycobacterial infection, the occurrence of which has not been clearly documented. For comparison, we also studied three cases of mycobacterial pseudotumor, of which 14 cases have been described to date. There was considerable histologic overlap between these two lesions. Acid-fast bacilli were present in all cases, predominantly in the more epithelioid histiocytes in the cases of Kaposi sarcoma, and in spindle and epithelioid cells in the cases of mycobacterial pseudotumor. The morphologic features that favored Kaposi sarcoma over mycobacterial pseudotumor were the prominent fascicular arrangement of spindle cells and slitlike spaces, the lack of granular, acidophilic cytoplasm, and the presence of mitoses. Immunohistochemistry was a reliable adjunct study in the differential diagnosis, as the spindle cells in mycobacterial pseudotumor were positive for S-100 protein and CD68 whereas those of Kaposi sarcoma were CD31- and CD34-positive but negative for S-100 protein and CD68. Awareness that Kaposi sarcoma may coexist with mycobacterial infection in the same biopsy specimen is important because these lesions may be misdiagnosed as mycobacterial pseudotumor. The clinical impact of distinguishing between Kaposi sarcoma with mycobacteria and mycobacterial pseudotumor is significant because the presence of Kaposi sarcoma alters treatment and prognosis.

Anthracotic and anthracosilicotic spindle cell pseudotumors of mediastinal lymph nodes: report of five cases of a reactive lesion that stimulates malignancy

We report five cases of reactive mediastinal spindle cell proliferations associated with anthracosis and anthracosilicosis that simulated a malignant process both on clinical and morphological grounds. Clinically, the lesions formed radiographically evident masses or were infiltrative. Microscopically, a prominent storiform pattern of intertwining spindle cells was found in four cases. This proliferation extended outside of the lymph node capsule in three cases and surrounded nerves in two. Because of this combination of features, the submitted diagnoses included a malignant neoplasm in four cases. The spindle cells were immunoreactive for histiocytic markers and focally contained fine anthracotic pigment. All cases featured nodular hyaline scars and contained polarizable material suggestive of silica, although a history of industrial exposure was obtained in only two cases. No lesion has enlarged or otherwise progressed during follow-up ranging from 6 to 48 months. The differential diagnosis includes a variety of spindle cell neoplasms, including malignant fibrous histiocytoma, follicular dendritic cell tumor, spindle cell melanoma, and Kaposi's sarcoma.

Penile mass caused by the newly described organism Mycobacterium celatum

We report a penile infection in a man with the acquired immunodeficiency syndrome caused by a newly described infectious organism, Mycobacterium celatum. Mycobacterium tuberculosis is the only mycobacterial species previously reported to cause infection in the penis. This is only the third documented human infection with M celatum, and the first to involve the genitourinary system.

Inflammatory pseudotumour of the mouth and maxilla

AIM

To describe the clinicopathological and immunophenotypical findings of two cases of inflammatory pseudotumour in the oral cavity.

METHODS AND RESULTS

The patients presented with a short history of swelling in the cheek and the maxilla respectively. Magnetic resonance imaging or computerised tomography scan showed space occupying lesions with infiltrative margins which were interpreted as aggressive malignant neoplasms. Histological examination showed fascicles of spindle cells in a background of chronic reactive inflammatory cells including plasma cells, typical of inflammatory pseudotumour. The spindle cells were positive for vimentin, smooth muscle actin and CD68, but were negative for follicular dendritic cell markers. The lymphocytes showed no light chain restriction.

CONCLUSIONS

Inflammatory pseudotumour in the oral cavity is completely benign and simple excision is curative. However, it may be confused with a malignant tumour on clinical and radiographic grounds, and histologically the appearances can also be misinterpreted as those of a more aggressive lesion. Its correct recognition by the surgical pathologist is important to avoid unnecessarily radical and potentially mutilating surgery.

Inflammatory pseudotumour of lymph nodes

AIM

To describe the clinical, histological and immunohistochemical features in four cases of an uncommon benign lymph node lesion which may mimic a neoplastic process.

METHODS

Four cases of inflammatory pseudotumour of lymph nodes were studied using conventional staining (haematoxylin and eosin, PAS, Gordon and Sweets reticulin stain, and the Ziehl-Neelsen stain) and with immunohistochemical techniques using a variety of antibodies (CD3, L26, CD15, CD21, CD30, KP1, MAC 387, vimentin, alpha SMA, HHF-35, D33, CD34, and S100).

RESULTS

The lesion comprises a proliferation of spindle cells expanding the connective tissue framework of lymph nodes and is associated with a plasma cell and small lymphocyte infiltrate. There are variable numbers of macrophages, neutrophils and eosinophils, and varying degrees of fibrosis. Vascular changes are common but vary in degree and type.

CONCLUSIONS

Inflammatory pseudotumour of lymph nodes is an uncommon benign reaction pattern which may be misdiagnosed as a neoplastic or even a malignant process. Increased awareness of its histological features should help prevent such misdiagnoses.

Post-radiation primary intranodal leiomyosarcoma

An unusual case of post-radiation primary intranodal leiomyosarcoma of the cervical lymph node is presented. The patient was a 32-year-old white man who was treated in 1986 with hemiglossectomy and right neck dissection, followed by radiation therapy, for squamous cell carcinoma of the tongue. Six years later, he presented with an enlarged left cervical lymph node which on biopsy showed a high grade spindle cell malignant neoplasm. Immunohistochemistry and electron microscopic study verified the smooth muscle origin of the tumour. Extensive work-up for a second primary lesion was negative. Primary intranodal leiomyosarcoma is extremely rare. We briefly discuss the histological differential diagnosis of spindle cell lesions of lymph nodes, leiomyosarcoma of the vessel wall and radiation-associated sarcoma.