NODULAR FASCIITIS AND RELATED PSEUDOSARCOMATOUS LESIONS OF SOFT TISSUES

Background: Nodular fasciitis is characterized by a proliferation of spindle cells which may be misdiagnosed as sarcomas due to the rich cellularity, mitotic activity and variant morphologic patterns. Methods: This report includes 42 cases of nodular fasciitis and related conditions of skin and soft tissue from the pathology files of the Royal Brisbane Hospital, Queensland, Australia. There were 33 cases of nodular fasciitis, three cases of ossifying fasciitis, three cases of proliferative fasciitis, two cases of proliferative myositis and one case of intravascular fasciitis. Two-thirds of cases were referred from outside Royal Brisbane Hospital. Results: Nodular fasciitis and ossifying fasciitis occurred most commonly in young adults with 16 patients (44%) between the ages of 20 and 29. However, the other variants of nodular fasciitis including proliferative fasciitis, proliferative myositis and intravascular fasciitis occurred in older people (six patients being older than 49 years) and more commonly occurring in men (n= 5). A painless, rapidly growing mass was most common. The lesions of nodular fasciitis were most often located in the upper extremity with the forearm most commonly affected. Conclusions: Nodular fasciitis and related conditions are benign. All patients are alive and well 3 months to 13 years (mean 7.2 years) after simple local resection.     

Nodular fasciitis. Its morphologic spectrum and immunohistochemical profile

Although nodular fasciitis (NF) is a well recognized pseudosarcomatous proliferation, it continues to cause diagnostic problems. We reviewed the clinical, histologic and immunohistochemical features of 53 lesions from 30 male and 23 female patients, ages 8-76 years, that involved the upper and lower extremities, trunk, and head and neck. Sizes ranged from 0.6 to 6.5 cm. The morphologic spectrum was broad, including the classic pattern of delicate fibroblasts suspended in a myxoid matrix, granulation tissue-like areas, solid and whorled myofibroblastic proliferations with multinucleated cells, mucoid cysts, and so-called "ancient" forms with dense, refractile strands of keloid-like collagen. Nodular fasciitis was correctly diagnosed in 23 cases (43%); a sarcoma was diagnosed in 11 (21%). A characteristic immunohistochemical profile emerged wherein 49 of 53 cases stained for smooth-muscle and muscle-specific actins, vimentin, and KP1 (a histiocyte marker), indicating dual myofibroblastic and histiocytic differentiation. None of the lesions expressed keratin, S-100 protein, or desmin. Knowledge of the immunohistochemical profile of nodular fasciitis and its overlap with certain sarcomas can decrease the likelihood of misdiagnosis.     

Intraoral proliferative myositis: case report and literature review

BACKGROUND: Proliferative myositis is a rare, benign, reactive intramuscular lesion of fibroblastic/myofibroblastic origin; an identical lesion in a subcutaneous or fascial location is referred to as proliferative fasciitis. The rapid growth rate and unusual histopathologic features have frequently been mistaken for a malignant process and have promoted unnecessary invasive procedures. Here we present only the third oral case of proliferative myositis, arising from the tongue of a 65-year-old man. METHODS AND RESULTS: Histologically, the resected lesion was composed of numerous fibroblastic or myofibroblastic spindle cells and variable numbers of large ganglion-like cells infiltrating between and around muscle fascicles, resembling a "checkerboard" configuration. A demographic profile of proliferative myositis of the head and neck is also provided, compiled from 19 patients culled from an English-language literature review and this report. CONCLUSIONS: Incisional biopsy or fine-needle aspiration biopsy of proliferative myositis of the head and neck should lead to spontaneous resolution and is, therefore, sufficient to render the diagnosis and to provide conservative treatment. Recurrence is extremely rare.     

Immunoreactivity for calretinin and keratins in desmoid fibromatosis and other myofibroblastic tumors: a diagnostic pitfall

Calretinin is an intracellular calcium-binding EF-hand protein of the calmodulin superfamily. It plays a role in diverse cellular functions, including message targeting and intracellular calcium signaling. It is expressed in the mesothelium, mast cells, some neural cells, and fat cells, among others. Because of its relative specificity for mesothelial neoplasms, calretinin is widely used as one of the primary immunohistochemical markers for malignant mesothelioma and in differentiating it from adenocarcinoma. On the basis of our sporadic observation on calretinin immunoreactivity in desmoid fibromatosis, we systematically evaluated calretinin, keratin cocktail (AE1/AE3), and WT1 immunoreactivity in 268 fibroblastic/myofibroblastic neoplasms. Calretinin was observed in 75% (44/58) of desmoid fibromatosis, 50% (21/42) of proliferative fasciitis, 23% (8/35) of nodular fasciitis, 33% (13/40) of benign fibrous histiocytoma, 35% (22/62) of malignant fibrous histiocytoma, and 13% (4/31) of solitary fibrous tumors but not in normal connective tissue fibroblasts at various sites. Keratin AE1/AE3 immunoreactivity was also commonly (6/13) present in the large ganglion-like cells of proliferative fasciitis and sometimes in nodular fasciitis (3/35), solitary fibrous tumor (3/27), and malignant fibrous histiocytoma (9/62). Nuclear immunoreactivity for WT1 or keratin 5 positivity was not detected in myofibroblastic tumors. On the basis of these observations, it can be concluded that calretinin and focal keratin immunoreactivity is fairly common in benign and malignant fibroblastic and myofibroblastic lesions. Calretinin-positive and keratin-positive spindle cells in desmoid and nodular fasciitis or calretinin-positive ganglion-like cells in proliferative fasciitis should not be confused with elements of epithelioid or sarcomatoid mesothelioma. These diagnostic pitfalls can be avoided with careful observation of morphology, quantitative differences in keratin expression, and use of additional immunohistochemical markers such keratin 5 and WT1 to verify true epithelial and mesothelial differentiation typical of mesothelioma.     

Intraarticular nodular fasciitis--a rare lesion: clinicopathologic analysis of a series

Nodular fasciitis is a benign myofibroblastic proliferation with a predilection for the subcutaneous tissues of the upper extremities, trunk, and head and neck of young adults. Nodular fasciitis is not generally recognized to arise within joints. In this study, the clinicopathologic and immunohistochemical features of 10 cases of intraarticular nodular fasciitis are described. Six patients were female and 4 were male, with a median age of 33 years (range, 9-50 years). Lesional size ranged from 2 to 4 cm (median, 2.6 cm). Seven tumors arose in the knee, 2 in the hand, and 1 in the ankle. Most patients complained of joint pain; 4 presented with a palpable mass. Only 1 patient reported antecedent trauma. The duration of symptoms prior to surgery ranged from 2 months to 1 year (median, 6 months). The clinical differential diagnoses included giant cell tumor of tendon sheath, pigmented villonodular synovitis, synovial chondromatosis, inflammatory arthritis, and lymphoma. Grossly, the lesions were solid, nodular, rubbery, or firm masses. Histologically, all tumors were circumscribed but unencapsulated and showed typical features of nodular fasciitis, being composed of cytologically bland plump spindle cells arranged in short, intersecting bundles within a variably loose myxoid to collagenous stroma, containing extravasated red blood cells and scattered lymphocytes. Five lesions showed prominent stromal hyalinization, in 2 cases keloidal in appearance. In 4 cases, the tissue at the periphery of the lesion showed hemosiderin deposition. By immunohistochemistry, all tumors examined were positive for SMA, 1 was positive for desmin, and all were negative for caldesmon and S-100 protein; none showed nuclear staining for beta-catenin. Clinical follow-up information was available for 5 patients, ranging from 2 to 86 months. No lesion recurred. In summary, intraarticular nodular fasciitis occurs most commonly in the knees of young adults, and often appears to have a somewhat longer preoperative duration than typical subcutaneous or intramuscular nodular fasciitis. Intraarticular lesions show morphologic features similar to other cases of nodular fasciitis, with the exception that stromal hyalinization and adjacent hemosiderin deposition are common, likely attributable to frictional trauma in this location.     

Inflammatory fibrosarcoma of the mesentery and retroperitoneum. A tumor closely simulating inflammatory pseudotumor.

We report 38 cases of inflammatory fibrosarcoma occurring in 23 females and 15 males, 2 months to 74 years of age (median, 8.5 years; mean, 15 years) with symptoms of abdominal pain (17 cases), anemia (21 cases), fever (14 cases), mass (16 cases), and gastrointestinal obstruction (7 cases). Primary tumor sites included mesentery and retroperitoneum (31 cases), omentum (two cases), mediastinum (two cases), liver (one case), diaphragm (one case), and abdominal wall (one case). Sizes ranged from 2.4 cm to 20 cm (mean, 9.6 cm). Follow-up data in 27 cases revealed local recurrences in 10 patients, with multiple local recurrences in three and histologically proven distant metastases to lung (two cases) and brain (one case). Five patients died from their disease (median, 20 months). All tumors, including metastases, consisted of fibroblasts, myofibroblasts, and plasma cells, with variable degrees of fibrosis and calcification. Immunostains indicate myofibroblastic differentiation; 18 of 20 (90%) stained for actin, 15 of 18 (83%) for vimentin, and 10 of 13 (77%) for keratin (primarily in a submesothelial location). Ultrastructural studies also disclosed myofibroblastic features. The locally aggressive, recurrent nature of these neoplasms, as well as the occurrence of metastases and tumor deaths, indicate that they are potentially malignant neoplasms that we believe are better classified as inflammatory fibrosarcomas, not as cellular inflammatory pseudotumors.     

Is calcifying fibrous pseudotumor a late sclerosing stage of inflammatory myofibroblastic tumor?

Calcifying fibrous pseudotumor is a recently described distinctive lesion, characterized by the presence of abundant hyalinized collagen with psammomatous or dystrophic calcifications and a lymphoplasmacytic infiltrate. The cause and pathogenesis are unclear, but a possible relationship with other pseudotumors, like nodular fasciitis or inflammatory myofibroblastic tumor, has been proposed by some authors. However, cases with overlapping histologic features have not been reported. A 17-year-old girl with multiple peritoneal calcifying fibrous pseudotumors and inflammatory myofibroblastic tumors (inflammatory pseudotumors) is described. Some multinodular lesions showed calcifying fibrous pseudotumors next to inflammatory myofibroblastic tumors. Transitional stages between calcifying fibrous pseudotumor and inflammatory myofibroblastic tumor were also present. This case clearly illustrates a histogenetic relationship between calcifying fibrous pseudotumor and inflammatory myofibroblastic tumor, and it suggests that calcifying fibrous pseudotumor is a late sclerosing stage of inflammatory myofibroblastic tumor, at least in some cases.     

Atypical decubital fibroplasia. A distinctive fibroblastic pseudotumor occurring in debilitated patients.

We report 28 cases of atypical decubital fibroplasia, a distinctive pseudosarcomatous fibroblastic proliferation occurring primarily but not exclusively in physically debilitated or immobilized patients. The subjects included 16 women and 12 men ranging in age from 15 to 95 years. Peak incidence was in the 8th and 9th decades of life. Anatomic locations included the soft tissues overlying the shoulder (eight cases), posterior chest wall (five cases), sacrum (five cases), greater trochanter (four cases), buttock (two cases), thigh (two cases), and arm (two cases). Symptoms were due to a painless mass of 3 weeks' to 6 months' duration. Most lesions were ill-defined, focally myxoid masses that ranged from 1 to 8 cm. Histologically, they were situated in the deep subcutis and secondarily involved adjacent skeletal muscle (11 cases) and tendon (three cases). Extensive epidermal ulceration was typically absent. Microscopically, the lesions had a lobular configuration. They were characterized by zones of fibrinoid necrosis and a prominent myxoid stroma rimmed by ingrowing, ectatic, thin-walled vascular channels. All cases contained atypical, enlarged, degenerated fibroblasts with abundant basophilic cytoplasm, large hyperchromatic, smudged nuclei, and prominent nucleoli; these features resulted in a superficial resemblance to proliferative fasciitis. The enlarged, atypical fibroblasts stained diffusely and strongly for vimentin (15 of 15 cases) and focally for muscle-specific actin (10 of 15 cases), keratin (one of 15 cases), CD68 (10 of 15 cases), and CD34 (five of nine cases) antigens; none of the cases stained for desmin. A malignant diagnosis was considered in 43% of cases. Follow-up in 21 patients ranged from 2 to 78 months (median, 12 months). Two lesions recurred once, one recurred twice, and none metastasized; no deaths were attributable to the lesions. The clinical, histologic, and immunohistochemical features of atypical decubital fibroplasia indicate it is a unique type of pressure sore displaying degenerative and regenerative features distinct from decubitus ulcer. Its recognition by pathologists and clinicians in elderly and debilitated patients is important to avoid misdiagnosis as a sarcoma and to prevent or minimize the occurrence of decubital fibroplasia in progressively aging patient populations.     

Postoperative cranial fasciitis. Report of two cases and review of the literature

The authors report two cases of cranial fasciitis occurring at prior craniotomy sites. They review the presentation and pathological features associated with cranial fasciitis and describe two unusual cases and their treatment. The first case is that of a 16-year-old girl who underwent suboccipital craniectomy for resection of medulloblastoma and 14 months later was found to have a 4-cm nontender mass at the incision site, with evidence of skull erosion on neuroimaging. Resection of the mass revealed cranial fasciitis. The patient later developed two more lesions in the cranial region, as well as lesions on the chest wall and abdomen consistent with nodular fasciitis; all of the lesions were resected. The second case is that of a 61-year-old man who underwent suboccipital craniectomy for hypertensive hemorrhage and 2 years later was found to have an enlarging mass at the incision site, causing compression of the cerebellum. The mass was resected and found to be consistent with cranial fasciitis. Cranial fasciitis is a rare, benign lesion of the cranial region. It is histologically identical to nodular fasciitis, a self-limiting fibroblastic process of the superficial and deep fascia. Although most cases of cranial fasciitis are reported to occur spontaneously in the very young, the two cases reported here involved older patients and lesions that developed at prior craniotomy sites in a delayed fashion, a phenomenon not previously reported. Interestingly, one patient exhibited lesions in other areas as well.     

Ischemic fasciitis: analysis of 44 cases indicating an inconsistent association with immobility or debilitation

Ischemic fasciitis is a rare pseudosarcomatous proliferation of atypical fibroblasts described to be located over bony protuberances and said to develop most often in immobile elderly or debilitated patients. We report the clinicopathologic features of 44 cases of this pseudosarcomatous reactive fibroblastic/myofibroblastic proliferation. There were 15 female and 29 male patients between 23 and 96 years of age (median: 74 y). Tumor size, known in 34 cases, ranged from 1.3 to 10 cm (median: 4.7 cm). The lesions developed mostly in the deep subcutis (27 cases) and infiltration of deep dermis, muscle, and tendinous tissue was sometimes observed. In 3 cases, the lesion developed within skeletal muscle. In 33 cases (76.7%), the tumor was located around the limb girdles and sacral region; 5 tumors each (23.3%) occurred on the chest wall and the back. A history of physical debilitation could be confirmed in only 7 patients. Nine patients had a history of chronic or malignant diseases and 4 patients had a history of local trauma. The histologic hallmark of this reactive proliferation is a zonal appearance with central fibrinoid degeneration/necrosis and cystic changes surrounded by a granulation tissuelike vascular component, mixed with plump amphophilic reactive fibroblasts and myofibroblasts morphologically similar to proliferative fasciitis. Immunohistochemistry was performed in 18 cases, showing focal positivity for smooth muscle actin (37.5%), desmin (40%), or both (14.3%), underlining the fibroblastic/myofibroblastic nature of these lesions, whereas S-100 and Pan-keratin were consistently negative. Follow-up data were available in 13 cases and ranged between 6 and 72 months (median: 31.3 mo); local recurrence was observed in 1 case in which the patient was physically debilitated. Recognition of this distinct entity as a reactive process, by no means always associated with debilitation, is essential to avoid confusion with soft tissue sarcomas.     

Desmoplastic fibroma of bone. An ultrastructural study

The ultrastructure of three cases of desmoplastic fibroma of bone is presented. The lesion is principally characterized by myofibroblasts admixed with lesser numbers of fibroblasts and primitive mesenchymal cells. Thus, the cellular composition is similar to that described in a variety of nonneoplastic proliferative processes of soft tissue. It is postulated that the myofibroblastic proliferation develops in response to unknown factors acting on marrow fibroblasts or primitive mesenchymal cells.     

Postoperative spindle cell nodules of genitourinary tract resembling sarcomas. A report of eight cases

Eight cases of proliferative spindle cell nodules that developed 5 weeks to 3 months after operations on the lower genital tract of four women, and the lower urinary tract of four men, are described. The lesions ranged up to 4 cm in diameter, resembled spindle cell sarcomas on microscopical examination, and were initially interpreted as such in most of the cases. Six of the lesions were treated by local excision alone, and two by a radical surgical procedure, followed by radiation therapy in one case. The six patients whose lesions were treated inadequately on the assumption that they were sarcomas were free of disease 9-60 months (average, 28 months) postoperatively, and the two men who were treated by radical procedures were well 18 and 60 months later. The microscopic features, the unusual clinical setting, and the favorable prognosis of these lesions suggest that they were examples of a hitherto undescribed form of benign reactive lesion resembling a sarcoma.     

Myofibrosarcoma: a clinicopathologic study

The concept of soft tissue sarcomas composed predominantly of myofibroblasts has been controversial. We examined a series of such lesions of low- and intermediate-grade malignancy to further define their clinical and pathologic features. Histologic appearances of four cases diagnosed as myofibrosarcoma by electron microscopy were reviewed. Eleven additional cases with similar morphology were then identified from 249 tumors originally indexed as fibrosarcoma. Electron microscopy was performed on five of these, and immunohistochemistry was carried out on all cases for which material was available. There were 11 men and 4 women aged 33 to 73 years (median, 54 yrs; mean, 53 yrs). Lesions mainly involved the head and neck, extremities, and trunk and ranged in size from 1.5 to 12 cm. The tumors were composed of bland or pleomorphic stellate to spindled cells with eosinophilic cytoplasm and tapered nuclei in a collagenous stroma; 10 were grade 1 and five were grade 2. All sarcomas displayed fascicular or storiform patterns, and some of the grade 1 lesions superficially mimicked nodular fasciitis. Electron microscopy of nine cases showed myofibroblastic differentiation, and immunohistochemistry showed smooth muscle actin in 13 of 15 cases, muscle-specific actin in 7 of 9, desmin in 6 of 14, and cytokeratin in 0 of 11. Four of nine grade 1 and three of four grade 2 tumors recurred (one twice), and one grade 2 tumor metastasized to the lungs. Myofibrosarcomas are indolent low-grade or occasionally aggressive intermediate-grade sarcomas which can be recognized by light microscopy. Their clinical importance lies in the resemblance, particularly of low-grade examples, to reactive or pseudosarcomatous conditions.     

Fibroma of tendon sheath. A clinicopathologic study of 32 cases

We report 32 cases of fibroma of tendon sheath. Most cases presented as a painless mass in the distal portion of an extremity. Ganglion cyst was the most frequent clinical diagnosis. The median patient age was 30.5 years, and 60% of the patients were male. Only one lesion is known to have recurred. The lesions, which averaged 1.5 cm, were light tan, firm, and nodular. Histologic features common to all lesions were (a) a predominantly fibrous matrix containing (b) fibroblast-like spindle cells. Elongated, slitlike spaces were observed in many lesions, and nine cases had areas closely resembling nodular fasciitis. Myofibroblasts and fibroblasts were observed in the three cases studied by electron microscopy. The histologic findings were similar to those previously described for fibroma of tendon sheath. Although slitlike spaces are present in most instances, this finding is not specific for fibroma of tendon sheath, nor is it invariably present. Fasciitis-like changes have been noted in previous series. Our findings, as well as those from prior studies, indicate that fibromas of tendon sheath are heterogeneous. The diagnosis is made only after other fibrous, nodular lesions of the extremities are excluded. Fasciitis-like lesions heretofore classified as fibroma of tendon sheath are more appropriately classified as tenosynovial counterparts of nodular fasciitis.     

Proliferative myositis. An immunohistochemical and ultrastructural study

We studied four cases of proliferative myositis by the avidin-biotin-peroxidase complex technique, using a panel of 12 antibodies, and by electron microscopy. The aim was to clarify the nature of their constituent cells, specifically the giant ganglion-like cells and spindle cells, and to discuss the implications for histogenesis. In all cases, both cell types showed positive cytoplasmic staining with antibodies to vimentin, actin (C4), and alpha-smooth muscle actin-1, but in only one was there positive staining with desmin. No staining was obtained with factor XIIIa, muramidase, alpha-1-antitrypsin, myoglobin, S-100 protein, CAM 5.2, factor VIII-related antigen, or neuron-specific enolase. By electron microscopy, both types of cells were seen to contain numerous thin filaments, dense bodies, coated and pinocytotic vesicles, active and dilated rough endoplasmic reticulum, few microvilli, and incomplete desmosomal junctions. Our findings imply a myofibroblastic nature for the giant ganglion-like cells and spindle cells. Our observations also support the hypothesis that they are derived from a pericytic cell.     

Congenital reactive myofibroblastic tumor of the petrous bone: case report

OBJECTIVE AND IMPORTANCE: Myofibroblastic tumors are members of a diverse spectrum of neoplastic and quasineoplastic lesions that occur most commonly during childhood and typically involve soft tissues. We present a case of a congenital reactive myofibroblastic tumor of the petrous bone (i.e., cranial fasciitis) that was successfully treated with surgical excision. CLINICAL PRESENTATION: A newborn girl with congenital right facial palsy and deafness was noted during imaging evaluation to have a large enhancing mass that was destroying the right petrous bone and extending into the posterior and middle cranial fossae. INTERVENTION: After embolization, an open biopsy was performed, which revealed a moderately cellular, spindle cell neoplasm without mitosis or necrosis, with scattered lymphocytes, eosinophils, and multinucleated giant cells. The spindle cells demonstrated strong immunoreactivity for vimentin, muscle-specific actin, and alpha-smooth muscle actin, with prominent reticulin staining between individual cells. Staining for CD68, a histiocyte marker, was positive within the multinucleated giant cells and many of the spindle cells; CD34, S-100, and desmin staining was absent. On the basis of these findings, the lesion was classified as a reactive myofibroblastic tumor, consistent with a cranial variant of nodular fasciitis. Because of the large size and significant mass effect of the tumor, a resection was performed several days later, using a combined supra- and infratentorial approach. Dense adherence of the mass to the walls of the sigmoid sinus and the carotid artery precluded complete resection without sacrifice of these vessels, which was not performed because of the known potential of these tumors to remain stable or regress after extensive subtotal resection. The presumed residual tumor subsequently regressed, and the patient has exhibited no detectable residual disease in 2 years of follow-up monitoring. CONCLUSION: Reactive myofibroblastic tumors of the calvarium are uncommon lesions that superficially resemble sarcomas. Recognition of this diagnostic entity is important, to avoid unnecessary treatment with intensive adjuvant therapy. Although the management of these tumors relies predominantly on surgical resection, surgical decision-making should take into account the fact that small areas of residual disease can regress spontaneously.     

Undifferentiated (embryonal) sarcoma of the liver. A tumor of uncertain histogenesis showing divergent differentiation.

Pathologic features of eight cases of undifferentiated (embryonal) sarcoma of the liver (USL) in childhood were studied. Light microscopic examination showed a diffuse growth of spindle cells with occasional polygonal cells and multinucleated giant cells and also revealed focal areas of storiform pattern in four tumors, cambium layer formation in one tumor, and alveolar arrangement in one tumor. Immunohistochemical study showed positive staining of proliferating cells for suggestive histiocytic markers (A1AT in 6/6, A1ACT in 5/6, lysozyme in 4/6, and KP1 in 4/6) and for muscle markers (desmin in 4/6 and HHF35 in 3/6). Ultrastructural examination demonstrated that the individual tumors were composed of a mixture of cells having fibroblastic, histiocytoid, fibrohistiocytoid, myofibroblastic, and undifferentiated (primitive mesenchymal) morphologies. Also identified were cells with definite myoblastic morphology in three tumors: leiomyoblastic in one and rhabdomyoblastic in two. In conclusion, the tumor cells in USL show phenotypical diversity comparable to those of malignant fibrous histiocytoma with or without additional rhabdomyosarcomatous or leiomyosarcomatous differentiation.     

Primary histiocytic lymphoma of the central nervous system: a neoplasm frequently overshadowed by a prominent inflammatory component.

True histiocytic lymphoma, as defined by strict criteria, is a very rare neoplasm. We describe three cases occurring as primary tumors in the central nervous system. The patients, two females and one male, ranged in age from 11 to 69 years. The tumors involved the brain in two cases and spinal cord in one, with a size ranging from 7 to 17 mm. Two patients died at 4 months and 8 months, respectively, and one was alive with disease at 5 months. Pathologically, the tumors comprised groups and sheets of noncohesive large cells with pleomorphic vesicular nuclei, distinct nucleoli, and abundant eosinophilic cytoplasm. A dense inflammatory infiltrate consisting of neutrophils, lymphocytes, plasma cells, and histiocytes was present, with multiple foci of necrosis and abscess formation. All three cases demonstrated an identical immunophenotype: positive for CD68 and lysozyme; focally positive for S-100 protein, CD45RB, and CD4; and negative for CD3, CD20, CD21/CD35, CD1a, CD30, ALK1, myeloperoxidase, glial fibrillary acidic protein, and cytokeratin. The proliferative index ranged from 20% to 35%. Ultrastructural examination further confirmed the histiocytic nature of the tumor cells, characterized by irregularly folded or multisegmented nuclei and abundant cytoplasm containing lysosomes; Birbeck granules, interdigitating cell processes, and cell junctions were not found. Although the presence of abundant inflammatory cells could obscure the neoplastic histiocytes, making the distinction from inflammatory conditions difficult, awareness of this unusual histologic feature and the invariable finding of pleomorphic cells in some areas of the lesion permit the correct diagnosis to be made.     

Pathophysiology and Treatment of Streptococcal Toxic Shock Syndrome

We have recently encountered three cases of streptococcal toxic shock syndrome, each of which had a different cause. All the patients had inflammation of soft tissue in the lower extremities, and developed shock and multiple organ failure immediately after the clinical visit. The inflammation of soft tissue was necrotising fasciitis in one case, myositis in one case, and phlegmon in one. In the first case the debridement was incomplete, which resulted in an extensive ulceration. Wary of repeating this experience, we made an early diagnosis and did a thorough debridement in the second case. The patient was ultimately discharged without complications. It is rare that a patient with extensive myositis survives without amputation of the extremity. The third patient responded well to early treatment with antibiotics.