Proliferative myositis. An immunohistochemical and ultrastructural study

Transgelin is a novel marker of smooth muscle differentiation that improves diagnostic accuracy of leiomyosarcomas: a comparative immunohistochemical reappraisal of myogenic markers in 900 soft tissue tumors

Immunohistochemical use of myogenic markers serves to define smooth or skeletal muscle differentiation in soft tissue tumors. Establishing smooth muscle differentiation in malignant lesions can be challenging in some cases. We immunohistochemically examined 900 soft tissue tumors selected from the French Sarcoma Group's archived tissue collection, which contains a large number of leiomyosarcomas. The four most widely used smooth muscle diagnostic markers were evaluated (smooth muscle actin, desmin, h-caldesmon and calponin), and compared with a novel marker, transgelin. The diagnostic performance of each marker was statistically assessed in terms of sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) and accuracy (A), in leiomyosarcomas versus all other sarcomas including gastrointestinal stromal tumors (GIST), and second in leiomyosarcomas versus specific tumor types. In leiomyosarcomas versus all other sarcomas including GIST, transgelin emerged as the best diagnostic marker (Se: 83%, Sp: 82%, PPV: 67%, NPV: 92%, A: 83%), compared with smooth muscle actin (Se: 75%, Sp: 83, PPV: 66%, NPV: 89%, A: 81%), desmin (Se: 45%, Sp: 88%, PPV: 62%, NPV: 79%, A: 75%), h-caldesmon (Se: 50%, Sp: 90%, PPV: 67%, NPV: 81%, A: 78%) and calponin (Se: 76%, Sp: 70, PPV: 52%, NPV: 87%, A: 71%). In leiomyosarcomas compared with other specific tumor types such as undifferentiated pleomorphic sarcoma and myxofibrosarcoma, the accuracy for transgelin varied from 80 to 87% whereas it was lower for all other markers (between 51 and 80%). These results indicate that transgelin could be used in practice as an additional marker useful for decision making, especially in those tumors with incomplete immunophenotypes.

Fibroblastic and myofibroblastic tumors in children and adolescents

Fibroblastic and myofibroblastic tumors in children and adolescents are a relatively common group of soft tissue proliferations that range from reactive to hamartomatous to neoplastic, with a full spectrum of benign, intermediate, and malignant neoplasms. These lesions are diagnostically challenging because of morphologic and immunohistochemical overlap, despite significant clinical, genetic, and prognostic differences. The fibromatoses are a major subgroup, and all types of fibromatoses can occur in the 1st 2 decades of life. Intermediate and malignant fibroblastic-myofibroblastic tumors are an important group that includes variants of fibrosarcoma and other tumors with recurrent cytogenetic or molecular genetic abnormalities and low metastatic potential. Pathologic examination is enhanced by adjunct techniques, such as immunohistochemistry, cytogenetics, and molecular genetics, although morphology provides the ultimate criteria for a specific diagnosis. This article reviews the clinicopathologic features of fibroblastic and myofibroblastic tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents, the use of diagnostic adjuncts, and differential diagnoses.

Pseudosarcomatous Soft Tissue Lesions: A Review

Pseudosarcomatous soft tissue lesions are potential pitfalls to both clinicians and pathologists due to their clinical presentation, resemblances to malignant lesions and their rarity. They also have a wide range of differential diagnosis histologically due to their relatively non-specific morphology and natural history of evolving features. The difficulty can be exacerbated by samples obtained from curettings or small biopsies as the architecture of the lesion is very helpful in pointing to the correct diagnosis. Familiarity with these entities is needed to avoid misdiagnosis and unnecessarily radical surgery. Despite recent advances in immunohistochemistry and genetic studies, their diagnosis still rest primarily on a combination of clinical history, radiological findings and histologic morphology.

Pseudosarcomas of soft tissue

One of the most common and important pitfalls in soft tissue pathology are the so-called pseudosarcomas. These lesions are nonneoplastic; however, their rapid growth, hypercellularity, cytologic atypia, and mitotic activity makes them prone to be misinterpreted as sarcoma. The most common of these lesions are fibroblastic/myofibroblastic and matrix-forming proliferations, including nodular fasciitis, proliferative fasciitis and myositis, ischemic fasciitis, massive localized edema, myositis ossificans, and bizarre parosteal osteochondromatous proliferation and related entities. Most of these lesions rarely recur following simple excision; therefore, their accurate recognition helps prevent excessive therapy.

Application of immunohistochemistry to soft tissue neoplasms

CONTEXT

Soft tissue tumors are composed of numerous and complex diagnostic entities. Because of this complexity and the recognition of an intermediate malignancy category including some tumors with a deceptively bland histologic appearance, soft tissue tumors may represent a major diagnostic challenge to the general practicing pathologist.

OBJECTIVE

To correctly diagnose soft tissue tumors with the ancillary use of immunohistochemistry.

DATA SOURCES

Review of the current literature with emphasis on those tumors for which immunohistochemistry has proven to be particularly useful.

CONCLUSIONS

Immunohistochemistry plays an important role in the diagnosis of soft tissue tumors. One of its major utilities is to correctly identify a tumor as being of mesenchymal or nonmesenchymal origin. Once mesenchymal origin has been established, histologic subtyping according to specific cell lineage may be achieved with the use of lineage-specific markers. Tumors of uncertain cell lineage and tumors with primitive small round cell morphology are often characterized by a unique immunohistochemical phenotype. In this group of tumors, immunohistochemistry is most widely applied and is of greatest value. Despite the rapid development of molecular genetic techniques, immunohistochemistry still remains the most important diagnostic tool in the diagnosis of soft tissue tumors aside from recognition of morphologic features and clinical correlation.

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.

Proximal-Type Epithelioid Sarcoma: Report of Two Cases in the Perineum

The authors report two cases of perineal proximal-type epithelioid sarcoma in middle-aged men, age 51 and 43 years old. Both tumors were located in the right side. In the first patient a 7.5-cm, well-encapsulated tumor was completely excised. The second patient was a referral case with incomplete excision, but the computed tomography scan and magnetic resonance imaging showed a 14-cm nonencapsulated tumor involving the soft tissues of the inner thigh and perineum, as well as metastasis in right inguinal and retroperitoneal lymph nodes. Both neoplasms had a predominant solid pattern alternating with occasional discohesive areas. Both were composed of large oval to polygonal cells with vesicular nuclei, conspicuous nucleoli, and amphophilic to eosinophilic cytoplasm. Rhabdoid phenotype was identified in the second case only. The first neoplasm displayed 15% necrosis, 7 mitoses per 10 high-power field, focal vascular invasion, and no extracapsular invasion. The other exhibited 60% necrosis, 12 mitoses per 10 high-power fields, extensive vascular invasion, no distinct capsule, and invasion of the surrounding fatty tissue. Both were positive for vimentin, cytokeratin, epithelial membrane antigen, and CD34. Muscle-specific actin was negative in the first case and focally positive in the second. CD56 was positive in the second case and negative in the first case. Desmin, CD45, CD30, factor VIII, CD31, S100, HMB45, calretinin, and synaptophysin were negative in both. Since proximal-type epithelioid sarcoma can be confused with a number of other soft tissue tumors with epithelioid and/or rhabdoid features, the authors emphasize the immunohistochemical differential diagnosis.

Proliferative myositis: value of imaging

Imaging findings in a 52-year-old woman with proven proliferative myositis are described. US revealed preservation of continuous muscle bundles and patchy areas of hyperechogenicity, containing hypoechoic lines. MRI showed at T2-w sequences an ill-defined, hyperintense, intramuscular lesion, containing isointense lines. Subtotal enhancement, a nonenhancing geometrical web, and fascial enhancement were noted. In patients with painful growing masses, US and MRI correlation may suggest the diagnosis of proliferative myositis leading to biopsy, thus avoiding mutilating surgery.

Subungual myxoid pleomorphic fibroma

The authors report an example of pleomorphic fibroma in a unique site: the subungual space of the thumb. A 54-year-old man presented with paronychia and markedly thickened hyperkeratotic nail. The nail plate was removed, and an exophytic, red, friable, granulation tissue-like lesion was revealed subungually. The lesion was diagnosed clinically as pyogenic granuloma. Excisional biopsy was performed. Histologically, the lesion showed a hypocellular fibroma with myxoid areas and dilated blood vessels. Interspersed with ordinary appearing fibroblasts, there were bizarre, atypical fibroblasts with hyperchromatic and large, pleomorphic nuclei and multinucleated floret-like giant cells. These atypical cells showed strong immunoreactivity with antibodies against CD34 and vimentin. Occasional positivity was noted with factor XIIIa and alpha-1-antichymotrypsin, whereas no reactivity occurred with alpha-1-antitrypsin, actin, or S-100 protein. The entity of pleomorphic fibroma has been reported in many body sites; however, this is the first case to be reported in the subungual space.

Proliferative fasciitis of the forearm: case report with immunohistochemical, ultrastructural and DNA ploidy studies and a review of the literature

A case of proliferative fasciitis arising in the left forearm of a 56-year-old man was examined. The lesion was preceded by blunt trauma, measured 1.5 x 1.3 x 1.0 cm, was poorly circumscribed and appeared white to light gray on the cut surface. Light microscopic examinations revealed that spindle cells and giant cells with one or two nuclei and abundant basophilic cytoplasm were arranged without any organized patterns in collagenous stroma. Ultrastructurally, well-developed rough endoplasmic reticulum separated by varying amounts of fine to course fibrillar materials was detected in the giant cells. Only vimentin immunoreactivity was detected in both spindle and giant cells. The Ki-67 labeling index of spindle cells was 35% but that of giant cells was less than 5%, and this reflects the quiescent or slow-growing features of these giant cells in proliferative fasciitis. DNA content of the cells, which was examined by image cytometry, demonstrated diploidy in both spindle (DNA index=1.01) and giant (DNA index=1.09) cells.

Atypical decubital fibroplasia in a young patient with melorheostosis

A case of atypical decubital fibroplasia of the right forearm arising in a 25-year-old male with melorheostosis is presented. The diagnosis of melorheostosis involving the right-sided bones was made by radiographical studies, and the patient has been obliged to use crutches due to the contracture and limited range of motion of the right leg. Two painless masses occurred in the subcutis of the posterior aspect of the right forearm over the excrescences of the underlying ulna due to melorheostotic deformity. Grossly, ill-defined firm masses, which measured 3 x 6 x 1.5 cm and 4 x 5 x 1 cm, respectively, were white and intermingled with yellow fatty tissue. Histologically, the lesions consisted of a proliferation of plump fibroblastic cells with abundant collagenous stroma. Vascular proliferation and occasional eosinophilic degeneration of the collagen fibers were also seen. The gross and histological features were those of atypical decubital fibroplasia (ischemic fasciitis). Immunohistochemically, the plump fibroblastic cells were positive for vimentin, but negative for desmin, muscle specific actin, and alpha-smooth muscle actin. Chondroid metaplasia was focally noted and round-shaped cells within this area were positive for S-100 protein. This lesion seemed to be a fibroblastic response against the long-standing, intermittent ischemia of the subcutaneous tissue between the bony excrescences due to melorheostosis and the weight-bearing forces of the crutch.

Chromosomal anomalies in a case of proliferative myositis

Proliferative myositis, a reactive lesion similar to proliferative fasciitis and nodular fasciitis, has only been cytogenetically described in one other report to date. This previously described case showed trisomy 2. Cytogenetic analysis and fluorescence in situ hybridization (FISH) of a proliferative myositis lesion in the present study did not reveal trisomy 2 but the following clonal translocation was observed: 46,XX,t(6;14)(q23;q32).

Localized myofibroblastic proliferation in the neck of a patient with an IgG myeloma

We describe a myofibroblastic proliferation in the neck and lower part of the face involving skin and muscle of a 68-year-old female patient with an IgG kappa myeloma. Biopsies showed a fusocellular proliferation with scarce pseudoganglion cells involving the superficial fascia and the cutaneous muscle of the neck. The proliferative cells showed immunohistochemical and ultrastructural features characteristic of myofibrobasts with a proliferating cell nuclear antigen index of 48%; 42% of the cells displayed HLADR-positive membrane staining. Cellular proliferation subsided following the use of immunosuppressive drugs. Eight months after initial consultation, the patient developed polymyositis without a proliferative component and died of aplastic anemia.

Focal myositis of the floor of mouth: report of two cases and review of the literature

Focal myositis is an uncommon inflammatory myopathy of unknown cause affecting skeletal muscle. It may be mistaken on clinical evaluation for a malignant neoplasm. We describe two cases, both involving the mylohyoid muscle of the floor of the mouth. In each case excisional biopsy of a firm indurated mass revealed a focal lymphocytic and histiocytic infiltrate associated with degenerating and regenerating skeletal muscle fibers. No clinical or biochemical evidence of generalized muscle disease was seen at presentation or at 1-year and 7-year follow-up examination. The literature on focal myositis involving the head and neck region is reviewed.

Pseudomalignant spindle cell proliferations of the urinary bladder

Twelve cases of polypoid, nonrecurrent, pseudomalignant spindle cell proliferations of the urinary bladder (eight women and four men) were analyzed. Two patients had a simultaneous urinary bladder carcinoma. The lesions were characterized by proliferating spindle- or strap-shaped cells, which on electron microscopic examination (performed in all 12 cases) revealed characteristics of fibroblasts and myofibroblasts. The cells showed immunoreactivity for vimentin in all cases, for alpha-smooth muscle-specific and muscle-specific actin in six cases, for cytokeratins in five cases, and for CD 34 in one case. No immunoreactivity was observed for desmin, myoglobin, epithelial membrane antigen, S-100 protein, endothelial cell antigen (H and Y), CD 68, or factor VIII RAG. Immunoreactivity for Ki-67 and proliferating cell nuclear antigen was detected in up to 30% of the spindle cell nuclei. The static cytometric DNA analysis revealed a diploid, or in two cases a hyperdiploid, stem cell line. An awareness of this type of spindle cell lesion and its immunophenotypic characteristics and diversity is of importance to avoid an erroneous diagnosis of spindle cell sarcoma (in particular leiomyosarcoma and embryonal rhabdomyosarcoma) or spindle cell carcinoma.