Absence of Gluteal muscle

A Case Presentation With Flow Cytometric Analysis and Literature Review

* We report a case of solitary unifocal Langerhans' cell histiocytosis presenting as a large lower extremity soft tissue mass in a 48-year-old white man. Radiologically, this was an infiltrating mass involving all compartments of the right thigh; the mass had a maximum diameter of 18 cm. Extensive evaluation revealed no evidence of involvement of any other organ. An incisional biopsy was performed under the presumptive clinical impression of sarcoma. A definitive diagnosis of Langerhans' cell histiocytosis was established on the basis of characteristic morphologic features, cell surface marker findings by immunohistochemistry and flow cytometry, and electron microscopic studies. The patient was treated with four courses of chemotherapy (etoposide and prednisone) and had no evidence of disease 3 years after the initial presentation. A review of the literature revealed that soft tissue Langerhans' cell histiocytosis usually presents in the head and neck area of children and usually has associated bone, lung, or reticuloendothelial system involvement. To our knowledge, this is the first reported case of solitary Langerhans' cell histiocytosis in an adult in which the presentation mimicked sarcoma. (Arch Pathol Lab Med. 1997;121:169-172)

The term Langerhans' cell histiocytosis (LCH) encompasses a set of closely related clinicopathologic disorders unified by a common proliferating element, the Langerhans' cell. The syndrome includes three forms: a unifocal variant, known as eosinophilic granuloma; a multifocal form, Hand-Schuller-Christian disease; and a more aggressive and often fatal form, Letterer-Siwe disease. Many synonyms have been used to designate these disorders, including histiocytosis X, type II histiocytosis, Langerhans' cell granulomatosis, histiocytosis "forme cutanee pure," and a generic term "non-lipid reticuloendotheliosis." The Langerhans' cell is now considered the dendritic cell of the epidermis, and it is believed to be derived from a multipotent bone marrow stem cell.2 The term mononuclear-macrophage and immunoregulatory effector system (M-PIRE) has been proposed3 to include the diseases with histiocytic differentiation. Others have proposed a four-class system to encompass different diseases with histiocytic derivation.2 In the latter system, LCH is considered a class I disease.

Langerhans' cell histiocytosis usually affects children and young adults and can be divided into three main clinical syndromes based on the number of lesions and the extent of organ involvement.56 The unifocal variant, eosinophilic granuloma, commonly involves bone, lymph nodes, or lungs as a primary target. The multifocal variant, Hand-Schiller-Christian disease, affects younger patients, and several sites in one organ system (mostly bone) are involved. In the disseminated histiocytosis (many cases of Letterer-Siwe disease), multiple sites in multiple organ systems are involved. Patients with the latter form are almost always infants or young children and suffer the worst outcome.5-7 Solitary soft tissue involvement has been reported infrequently in the literature and most of these cases were in the head and neck region, skin, lung, and reticuloendothelial system of children and young adults.

We present a unique case of a solitary soft tissue LCH mimicking sarcoma, without bone involvement, in a 48-year-old white man. We describe the radiologic, histologic, immunophenotypical, and ultrastructural features of the tumor, as well as the treatment protocol and clinical follow-up.

REPORT OF A CASE

A 48-year-old white man presented to Shands Hospital at the University of Florida, Gainesville, with a 3-week history of right thigh swelling. Radiologic workup by computed tomographic scan and magnetic resonance imaging revealed a large soft tissue mass, up to 18 cm in maximum diameter, involving all three compartments of the thigh (Fig 1) and extending to the gluteal muscles of the right hip. No other lesions were found. After establishing the diagnosis, the patient was treated with four cycles of etoposide and prednisone, and he has no evidence of disease 3 years after the initial presentation.

PATHOLOGIC FINDINGS

An incisional biopsy revealed skeletal muscle diffusely infiltrated by a relatively monomorphic tumor composed of large cells with elongated irregular nuclei, prominent nuclear grooves and indentation, moderate to abundant cytoplasm, and frequent mitotic figures. An associated mixed inflammatory cell infiltrate composed of polymorphonuclear cells, eosinophils, and small mature-appearing lymphocytes were also noted. The large cells were immunoreactive for S100 protein. Electron microscopic examination showed nuclear indentation and the characteristic Birbeck granules (Fig 2).

Immunophenotypic analysis was performed on a Facscan flow cytometer (Becton-Dickinson Immunocytometry Systems, San Jose, Calif). Single-cell suspension from representative fresh tissue was prepared as described elsewhere.8 Wright-Giemsa-stained cytospin preparations from the resulting cell suspension were morphologically examined for sample adequacy. Immunofluorescence and DNA stains were performed and analyzed as previously described.9 Nonviable cells were excluded from the analysis by propidium iodide staining. All antibodies used in this study were from Becton-Dickinson Immunocytometry Systems, except for CD1 (Ortho Diagnostics System Inc, Raritan, NJ) and antibodies against heavy and light immunoglobulin chains (Caltag Laboratories, San Francisco, Calif/Tago Immunologicals, Inc, Burlingame, Calif). Flow cytometric findings revealed that Langerhans' cells strongly expressed CD1 (Fig 3), CD45, HLA-DR, CD4, and CD33. CD2, CD13, and CD71 were weakly expressed, and CD3, CDS, CD7, CD8, CD10, CD11c, CD19, CD20, CD25, CD34, and heavy and light immunoglobulin chains were not detected. CD14 expression was equivocal. Cell cycle analysis demonstrated a diploid population of cells, with a total S-phase fraction of 4%.

COMMENT

With the advent of immunophenotyping techniques in the last decade, our knowledge of LCH as a group of diseases is evolving. Whether these proliferative syndromes are reactive or neoplastic is still controversial.ll-12 In a recent clinicopathologic study of a large number of cases with long-term follow-up, Lieberman et all" concluded that LCH represents a reactive process analogous to sarcoidosis.lo However, Willman et al13 demonstrated in all their cases the clonal nature of Langerhans' cells in contrast to the polyclonal lymphocytes in the same lesions. This finding indeed favors a neoplastic process.

A review of the literature revealed reports from several different centers demonstrating their experience with cases of soft tissue LCH. However, none of the reported cases had a profile similar to ours (Table).67,1,14-24 This case illustrates that, in addition to soft tissue sarcomas, the differential diagnosis of infiltrating soft tissue masses should include LCH. Although the histologic, immunophenotypic, and ultrastructural features of the tumor we describe is classic for LCH,25-27 this case is unique in two aspects, namely, the relatively older age of the patient and the exclusive soft tissue location, which spared bone and other organs.

It is generally accepted that the prognosis of LCH depends on the extent of tissue involvement, organ dysfunction, and age of the patient.l56 Histologic features do not appear to predict the prognosis in this disease.5,6,l728 Our patient is free of disease 3 years after diagnosis. It may be premature to predict his long-term clinical outcome; however, his age, the solitary nature of the lesion, and the dramatic response to chemotherapy may suggest a favorable outcome. Interestingly, the treatment used in our patient consisted of chemotherapy alone, in contrast to the usual proposed protocols of radiation therapy with or without chemotherapy.7,18,20,23,29

The immunophenotypic analysis confirmed that Langerhans' cells usually express CD45 antigen on frozen or fresh tissue, in contrast to their nonimmunoreactive response in formalin-fixed, paraffin-embedded tissue.25,28 Langerhans' cells were strongly reactive with anti-CD1 antibody, which is highly characteristic of this disease and is required for definitive diagnosis of LCH in the absence of Birbeck granules.4 It should be emphasized that it is presently possible to detect CD1 in the vast majority of cases, even in formalin-fixed tissue. The expression of CD2, although unusual, was reported in 7 out of 12 cases of LCH by de Graff et al.31 Since CD2 is not expressed by normal Langerhans' cells, this finding would represent an aberrant antigen expression and may support the hypothesis that LCH is a neoplastic process. Expression of CD13 and CD33 in our case is not surprising since Langerhans' cells are related to histiocytic/monocytic cells. However, we are unaware of any published reports addressing the presence of these antigens on Langerhans' cells.

Our results regarding DNA content analysis showed a diploid population of cells. This finding is in agreement with a previous study using paraffin-embedded tissues, which failed to show aneuploidy in 37 specimens analyzed,32 although aneuploidy was detected in two cases using fresh tissue.33,34Therefore, it appears that Langerhans' cells in these proliferative syndromes are predominantly diploid in nature. As expected in a low-grade proliferative disorder, the S-phase fraction in our case was low.

To our knowledge, this is the first reported case of LCH with such an unusual clinical presentation and dramatic response to chemotherapy.

This work was supported by the Department of Pathology, Immunology and Laboratory Medicine University of Florida, Gainesville.

The authors thank Sharon Weiss, MD, and Blaise E. Favara, MD, for their advice.

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Accepted for publication September 26, 1996. From the Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville. Dr Masih is now with the Department of Pathology, Holmes Regional Medical Center, Melbourne, Fla.

Reprint requests to University of Florida, Department of Pathology, Box 100275 JHMHC, Gainesville, FL 32610 (Dr Almasri).

Copyright College of American Pathologists Feb 1997
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