Intermediate and fine cytofilaments in cutaneous and subcutaneous leiomyosarcomas

Cutaneous Smooth Muscle Tumors: A Review

Smooth muscle tumors occur infrequently in the skin. They consist of a diverse group of lesions representing hamartomas as well as benign and malignant neoplasms. They may arise from arrector pili muscle, specialized smooth muscle of the genitalia, or vascular smooth muscle. Although rare, accurate diagnosis and classification of cutaneous smooth muscle proliferations is important as they can exhibit a range of clinical behavior and may be associated with underlying syndromes. This review summarizes the clinicopathologic spectrum of smooth muscle tumors involving the skin.

Vascular leiomyosarcoma: Clinicopathology and immunohistochemistry with special reference to a unique smooth muscle phenotype

Vascular leiomyosarcoma (LMS) is the least frequent type of soft-tissue LMS and has not been fully evaluated immunohistochemically. The aim of the present study was therefore to examine four cases of vascular LMS, paying special attention to the immunohistochemical expression of smooth muscle markers. All the patients were female; two tumors were located within the inferior vena cava, one within the saphenous vein, and one within the external iliac vein. All the tumors displayed well-moderately differentiated smooth muscle morphology. On immunohistochemistry all four vascular LMS were diffusely and strongly reactive to actins, calponin, and h-caldesmon, whereas desmin was diffusely stained in one tumor, only focally positive in two, and negative in one. The walls of the blood vessels contiguous to the tumors contained desmin- and h-caldesmon-positive smooth muscle cells in two cases. In contrast, among 43 non-vascular LMS (20 well-moderately differentiated and 23 poorly differentiated or other types), 38 were variably positive for desmin, whereas 21 were negative for h-caldesmon. These findings suggest that the vascular LMS displays a distinctive phenotype of smooth muscle differentiation according to histopathogenesis.

Immunohistochemical detection of cytokeratin and epithelial membrane antigen in leiomyosarcoma: a systematic study of 100 cases

Although 'aberrant' expression of the epithelial markers, cytokeratin (CK) and epithelial membrane antigen (EMA), in leiomyosarcoma has been described previously, there has not been a study of this phenomenon with clinicopathological correlation in a large series of lesions at different anatomical sites. We investigated systematically the immunohistochemical reactivity for CK and EMA in 100 cases of leiomyosarcoma. CK and EMA were positive in 38% and 44% of the cases, respectively. Although staining was usually focal, extensive immunoreactivity was observed in 11% with CK and 6% with EMA. There was no correlation between immunoreactivity for CK and EMA in leiomyosarcomas and non-neoplastic smooth muscle at the same location. Immunoreactivity for CK and EMA was not correlated with the location, age, sex, histological grade, or histological features, except for more frequent EMA positivity in vascular and uterine tumors than in soft tissue cases. These results indicate that CK and/or EMA-positive leiomyosarcomas do not have distinctive clinicopathological features differing from those of negative cases. However, the considerable frequency of immunoreactivity for these epithelial markers in leiomyosarcoma, occasionally with diffuse and strong immunopositivity, should be recognized as a potentially serious diagnostic pitfall in the differential diagnosis of other malignant spindle cell neoplasms.

Expression of myogenic marker proteins in human leiomyosarcoma

A series of formalin-fixed, paraffin-embedded leiomyosarcomas (n = 11) was studied immunohistochemically for their expression of various myogenic marker proteins. According to their predominant histological appearance, the tumors were classified as well (n = 4), moderately (n = 5), or poorly (n = 2) differentiated. Using monoclonal anti-muscle specific actin antibodies from clone HHF35 all examined tumors were positively stained. Desmin was not always found in leiomyosarcomas, since positive staining could be demonstrated only in eight cases. As revealed by staining with anti-vinculin antibodies from clone hVIN-1 using the APAAP technique, all leiomyosarcomas with the exception of one expressed vinculin. Typically, the vinculin immunoreactivity was detected diffusely throughout the majority of neoplastic cells as well as in vascular smooth muscle cells of blood vessels. Nine leiomyosarcomas displayed a positive staining for calponin, an actin-binding protein expressed in smooth muscle cells and their precursors. The distribution of calponin resembled that of vinculin in decorating myofibrils of nearly all tumor cells. Actinin immunoreactivity was present in tumor cells of all cases, but was expressed also in nontumor cells such as epithelia. These results suggest that the monoclonal antibodies against vinculin and calponin may serve as additional diagnostic markers for myogenic differentiation in leiomyosarcomas and related tumors.

Cutaneous leiomyosarcoma

We report the clinical, histopathologic, immunohistologic, and prognostic findings in 19 patients with cutaneous leiomyosarcoma, eight males and 11 females (mean age, 66 years; age range, 41-93 years). The tumors presented mainly as solitary lesions and were located on the head and neck (eight lesions), trunk (four lesions), upper extremities (three lesions), and lower extremities (four lesions). Histopathologically, two predominant growth patterns were observed: nodular (12 cases) and diffuse (seven cases). Neoplasms with a nodular growth pattern were characterized by high cellularity and prominent nuclear atypia, and they showed conspicuous mitoses, several necrotic cells, and sometimes extensive necrotic areas. By contrast, most cutaneous leiomyosarcomas with a diffuse growth pattern revealed low cellularity, well-differentiated smooth muscle cells, inconspicuous mitotic figures, and few or no necrotic cells. Immunohistologic investigations revealed all cutaneous leiomyosarcomas to express vimentin and smooth muscle actin. Pan-muscle actin (HHF-35) was also expressed in most cases (15 lesions). However, only 12 lesions showed positive staining for desmin. Remarkable was the expression of cytokeratins in five lesions. Clinical follow-up revealed local recurrences in five patients (three cases with nodular pattern and two lesions with a diffuse pattern) after a period ranging from 8 months to 3 years after surgical excision. No distant metastases have been observed in our series. We conclude that cutaneous leiomyosarcoma with a diffuse growth pattern may constitute a pitfall in histopathologic diagnosis because of the presence of only subtle criteria for malignancy. Cutaneous leiomyosarcoma may show different immunophenotypes, thus emphasizing the importance of using a large panel of antibodies (smooth muscle actin, HHF-35, desmin, vimentin, cytokeratins, and S-100 protein) in immunohistologic diagnosis. Cutaneous leiomyosarcoma sometimes reveals local recurrences, but it has negligible potential for distant metastases.

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.

Immunoreactivity to cytokeratins in non-epithelial cells in deep gastric ulcer

The finding of cytokeratin positivity in non-epithelial cells in 9/15 cases of performing or penetrating gastric ulcer is reported. Two different monoclonal anti-cytokeratin antibodies were used and both produced a strong positivity in spindle and polyglonal cells in the gastric wall. These cells were often distributed near the peritoneal surface, but they were also found in central parts of the gastric wall. The cytokeratin-positive cells had no connection with the gastric mucosa, lacked epithelial features in routinely stained sections and were not positively stained by antibodies to other epithelial markers (EMA and Ber-Ep 4). Many of the cytokeratin-positive cells were also positive for vimentin. There was no evidence of malignancy in any of the cases, but cytokeratin-positive cells like those in the present study may be erroneously interpreted as infiltrating carcinoma. The true nature of the cytokeratin-positive cells was not revealed in the present study. It is concluded that cytokeratin positivity must be evaluated with care and that it is valuable to add antibodies other than anti-cytokeratins for the recognition of epithelial cell differentiation.