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Ossifying fibromyxoid tumor of soft tissues (OFMT) is considered a rare mesenchymal neoplasm. Its main histological features are sheets and ill-defined lobules of rounded bland cells within a fibromyxoid background and a thick collagenous capsule with an incomplete rim of lamellar bone. This lesion occurs mostly in the soft tissues of the lower extremities and limb girdles. In this paper, we describe a mesenchymal tumor removed from the right thigh of a 41 year-old-woman. The neoplasm differed histologically from typical forms of OFMT for areas of moderate cellularity and atypia, nuclear enlargement and small nucleoli. Focally, stromal tongues of osteoid were centrally and irregularly located within the lesion with evident spindling of tumor cells around them. The mitotic activity was low (up to 19 per 50 HPF) and atypical figures were rarely seen. The tumor was positive to S-100 protein, vimentin, CD10, CD56, CD99, ASMA, calponin and collagen IV. Rare elements were positive for cytokeratin AE1/AE3. To the best of our knowledge, this is the first case of atypical OFMT reported to be positive for calponin. The patient is currently alive and well with no evidence of disease at 96 months following surgery. In spite of low-grade histology, OFMT has high local recurrence rate and low metastatic potential, primarily in the lungs, even several years after surgical removal. The recognition of this entity is important. In this report the authors address differential diagnosis and enigmatic histogenesis of this neoplasm.

Pleomorphic hyalinizing angiectatic tumor (PHAT) is considered an unusual mesenchymal tumor of intermediate malignant potential that is distinguished by a prominent angiectatic vasculature with clusters of thin-walled, fibrin-lined vessels surrounded by sheets of spindled and pleomorphic cells. This lesion occurs mostly in the subcutaneous soft tissues of the lower extremities. In this paper, the authors report the first case of PHAT involving the breast parenchyma of a 75-year-old man. The patient was referred to the hospital with a history of a painless left breast mass that had been growing for several years. The lesion did not recur after surgery. The tumor exhibited histopathologic and immunohistochemical features identical to those of a PHAT of other sites. The purpose of this report is to add a rare tumor to the differential diagnosis of mammary spindle cell neoplasms.

We describe a rare case of myopericytoma-type perivascular myoma (MTPM) which arose in acral location and the literature on this field is briefly reviewed. The patient, a 68-year-old man, presented with an enlarging painful nodule, 1.4 cm across, located in the subcutaneous tissue of the right foot. The patient is alive and well 17 months after surgical excision of the nodule. Microscopically, the lesion was well-circumscribed and characterized by a biphasic pattern with a concentric perivascular spindle and ovoid cell proliferation and an extensive hemangiopericytomatous growth component. Immunohistochemically, the neoplastic cells were positive for vimentin, smooth muscle actin, desmin and calponin, negative for S-100 protein, CD34, CD31 and cytokeratins (AE1/AE3, Cam 5.2). Electron microscopy showed electrondense cell bodies suggestive for myopericytic differentiation. The clinico-pathological features of the present case are similar to those previously reported in the literature and we also discuss herein the main histological criteria for the differential diagnosis with other spindle cell and vascular lesions of soft tissues.