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Myofibroblastoma (MF) is an uncommon, usually benign, mesenchymal tumor infrequently described in soft tissues. We report here on the clinicopathologic findings of a soft tissue MF (STMF) presenting in the neck of a 90-year-old man as a slowly growing and non-painful nodule, 4 cm in greatest diameter. Histology revealed a circumscribed lesion constituted of monomorphous bipolar spindle cells arranged in swirling fascicles with intervening broad bands of hyalinized collagen and well formed “amianthoid” fibers. Immunohistochemistry showed the spindle cells to be immunoreactive for vimentin, smooth muscle actin and muscle specific actin and, focally, for desmin; im-munostaining for cytokeratin, epithelial membrane antigen, S-100 protein, factor VIII-related antigen, and CD34 was negative. Based on the present case and on those previously reported in the literature, STMF is characterized by: 1) exclusive incidence in the male sex; 2) variable immunoreactivity of the neoplastic cells for desmin, probably reflecting an origin from a peculiar subset of myofibroblasts, or, alternatively, a further myoid differentiation; 3) variable abundance of (hyalinized) collagen; 4) presence of amianthoid fibers. The combination of desmin immunoreactivity, frequently observed in MF of the breast, and amianthoid fibers, the main feature of MF of the lymph nodes, has never been observed in soft tissue MF. It is important to recognize STMF as a specific clinicopathologic entity to avoid confusion with other types of spindle cell proliferation and to differentiate it from other types of myofibromatosis.

We report on a 4-year-old boy with recurrent giant-cell fibroblastoma of the right nasal genal region. Histologic examination revealed that both lesions were constituted of spindle and stellate cells and a minor amount of multinucleated giant cells in a myxoid stroma containing cisternal-like spaces. Immunohistochemical examination revealed positivity for vimentin in both cellular components. Ultrastructural examination showed, in some spindle and multinucleated cells, two kinds of intracellular crystalline inclusions, located, respectively, in the cisternae of the rough endoplasmic reticulum and, apparently free, in the cytoplasm. To the best of our knowledge, this case, unusual for its location, is the first example of giant-cell fibroblastoma bearing intracellular crystalline inclusions.

A 43-year-old man underwent surgical removal of L4-L5 nerve root tumor which bulged to the extra and intradural spaces and extended as a dumbbell through the intervertebral foramen. Histological examination showed pleomorphic tumor cells with heavy melanin pigmentation. Most of the tumor cells were immunohistochemically positive for vimentin, S-100 protein and HMB-45 antigen; basic myelin protein was detectable in single tumor cells. Electron-microscopy revealed melanosomes in different stages of differentiation and some characteristics of Schwann cells, such as redundant basal lamina production. Taken together the tumor showed features of histological malignancy and incomplete schwannian differentiation with considerable overlap between melanoma and malignant melanotic schwannoma.

Background Congenital-infantile fibrosarcoma is a rare tumor of the pediatric age. It involves subjects under 5 years of age, and more than 200 cases have been reported in the literature. Methods The authors present the clinicopathologic findings of 2 cases and review the literature. Results Of our 2 patients, the first was a 2-years and 6-months-old female and the second a newborn male. The female presented a tumor in the retroperitoneum without recurrences or metastasis after 17 months, and the male on left foor with a recurrence after 3 months. Histologically, the tumors were mainly composed of spindle-shaped cells. Immunohistochemically, in both cases, neoplastic cells were positive for vimentin; focal positivity for muscular specific actin was present in the tumor of the female. Ultrastructurally, tumors were composed of mesenchymal cells with fibroblastic and myofibroblastic features. Flow cytometric analysis of the retroperitoneal tumor showed an aneuploid population of neoplastic cells. Conclusions Congenital-infantile fibrosarcoma should be considered a borderline tumor; its biologic behavior is better than that of adult fibrosarcoma. Histologic diagnosis is not easy; the microscopic picture may be confused with fibromatosis or with malignant mesenchymal neoplasms. Only a follow-up of many years can confirm the benignancy or malignancy of any individual tumor, even though clinico-pathologic features may be distinctive enough to permit its recognition.

A careful overview of the classical appearances of Kaposi's sarcoma (KS) as well as of its variants were reviewed from the clinical and pathological point of view. The growth phases (stages) and the cellular patterns were histopathologically compared with emphasis on the developmental progression of disease as well as mitotic activity. Other morphological aspects were also assessed such as the features of the early phases and the incidence of hyaline bodies. One hundred and forty-three lesions from 96 patients mostly of the Italian sporadic type were investigated. A complete list of those entities which should be considered in differential diagnosis is shown and the dilemma of whether KS is a neoplasia or a hyperplasia is discussed.