Epithelioid hemangioendothelioma is a unique tumor of adult life which is characterized by an “epithelioid” or “histiocytoid” endothelial cell. Forty‐one cases of this rare tumor have been recognized at the Armed Forces Institute of Pathology. They may occur in either superficial or deep soft tissue, and in 26 cases appeared to arise from a vessel, usually a medium‐sized or large vein. They are composed of rounded or slightly spindled eosinophilic endothelial cells with rounded nuclei and prominent cytoplasmic vacuolization. The latter feature probably represents primitive lumen formation by a single cell. The cells grow in small nests or cords and only focally line well‐formed vascular channels. The pattern of solid growth and the epithelioid appearance of the endothelium frequently leads to the mistaken diagnosis of metastatic carcinoma. The tumor can be distinguished from a carcinoma by the lack of pleomorphism and mitotic activity in most instances and by the presence of focal vascular channels. Ultrastructural study in four cases confirmed the endothelial nature of the tumor in demonstrating cells surrounded by basal lamina, dotted with surface pinocytotic vesicles, and occassionally containing Weibel‐Palade bodies. Follow‐up information in 31 cases indicated that 20 patients were alive and well following therapy; three developed local recurrences and six metastases. It is suggested the term epithelioid hemangioendothelioma be used to designate these biologically “borderline” neoplasms. The significance of the epithelioid endothelial cell is not entirely clear. Since it may be observed in both benign and malignant vascular lesions, its presence alone does not define a clinicopathologic entity.

The clinicopathologic findings in 200 cases of malignant fibrous histiocytoma (MFH) with follow-up information are presented. This tumor occurred principally as a mass on an extremity (lower extremity 49%, upper extremity 19%) or in the abdominal cavity or retroperitoneum (16%) of adults (peak incidence 61-70 years of age). It typically involved deep fascia (19%) o r skeletal muscle (59%) and only rarely was confined to the subcutis without fascia1 involvement (7%). The MFH had variable morphologic features and frequently showed transitions from areas having a highly ordered storiform pattern to less differentiated areas having a pleomorphic appearance. The rate of local recurrence of the tumor was 44%, and of metastasis, 42%. Metastasis was most frequently to the lung (82%) and lymph nodes (32%). Factors that influenced the rate of metastasis included depth, size, and inflammatory component of the tumor. Tumors that were small, superficially located, or had a prominent inflammatory component metastasized less frequently than larger, more deeply located tumors. In our experience the MFH is the most common soft tissue sarcoma of late adult life, and many tumors previously diagnosed as pleomorphic variants of liposarcoma, fibrosarcoma, or rhabdomyosarcoma are probably examples of MFH. Although the histogenesis of this neoplasm remains controversial, we feel it is best regarded as a primitive and pleomorphic sarcoma showing partial fibroblastic and histiocytic differentiation, as reflected by collagen production and occasional phagocytosis.

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The clinical and pathologic features of 61 cases of congenital and infantile myofibromatosis are presented. The tumor affected almost exclusively infants and young children; 88% of cases occurred before the age of two years, and 60% were noted at birth or shortly thereafter. Solitary (45 cases) and multicentric (16 cases) forms of the tumor could be distinguished; the solitary form was more common in males (69%) and affected chiefly the soft tissues of the head-neck region and the trunk. The multicentric form, on the other hand, predominated in females (63%) and was found not only in soft tissues but also in bones and viscera. Fourteen of the 16 cases with multicentric lesions were present at birth, and four of them had evidence of visceral involvement. Among the 16 cases were two sets of siblings, both brother and sister. Grossly, nearly all of the tumors were well demarcated; they measured from 0.5 to 7 cm in greatest diameter. Microscopically, they formed well-circumscribed nodules consisting of short bundles of plump, spindle-shaped cells displaying staining characteristics intermediate between fibroblasts and smooth muscle cells. Necrosis or a hemangiopericytoma-like pattern was often found in the center of the tumor nodules. Intravascular growth was encountered in several instances, but this feature did not seem to affect the clinical behavior. Of the 43 patients with follow-up data (mean-follow up 5.1 years), 36 were alive and well. Of the solitary lesions, three recurred. Of the multicentric lesions, five of the 15 patients showed evidence of spontaneous regression of both soft tissue and bone lesions. Four died, three of extensive involvement of multiple viscera, especially the lung, and one of "crib-death."

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