Ossifying fibromyxoid tumor of soft parts

A rare soft tissue tumor located in the trunk: Ossifying fibromyxoid tumor

Ossifying fibromyxoid tumor (OFMT), a rare soft tissue tumor, is generally located in the extremities with a distinct morphology characterized by bland, small cells lying in a fibromyxoid stroma and a peripheral rim of the lamellar bone. These tumors mostly express Leu-7, neuron specific enolase in addition to S-100 and vimentin. Some tumors may have malignant cytological features with aggressive behavior but even in classical morphology, recurrence or metastasis can be detected. Thus, the outcome of the tumor remains a mystery and depends on the different results detected during the follow up. Herein, we report a case of OFMT regarding this entity in the differential diagnosis of subcutaneous masses.

Ossifying fibromyxoid tumor of soft parts: a clinicopathologic, proteomic, and genomic study

Ossifying fibromyxoid tumor (OFMTs) of soft parts is a rare soft tissue and bone tumor of borderline malignancy displaying an uncertain line of differentiation. The existence of fully malignant OFMT is controversial. To better understand the natural history and line of differentiation taken by OFMT, we studied 46 cases by light microscopic, immunohistochemical (IHC), genomic, proteomic, and fluorescence in situ hybridization (FISH) methods. Cases were classified according to the 2003 Folpe and Weiss system. Clinical and follow-up information was obtained. IHC for S-100 protein, desmin, epithelial membrane antigen (EMA), cytokeratins, smooth muscle actin (SMA), INI-1, neurofilament protein (NFP), CD56d excitatory amino acid transporter-4 (EAAT4), and MUC4 was performed on formalin-fixed, paraffin-embedded (FFPE) tissues. Gene expression profiling and proteomic studies were conducted on FFPE tissues from 13 and 5 cases, respectively. FISH for INI-1 was performed on 10 cases. The 46 tumors arose in 29 men and 17 women (median age, 52 y; range 39 to 63 y) and involved the proximal (N=17) and distal extremities (N=13), head and neck (N=9), and trunk (N=5). Median tumor size was 5.4 cm (range, 1.0 to 21.0 cm). Cases were classified as typical OFMT (26 of 46, 57%), atypical OFMT (5 of 46, 11%), and malignant OFMT (15 of 46 cases, 32%). Clinical follow-up (27 cases, median 55 months' duration) showed all patients with typical and atypical OFMT to be alive without disease. Adverse events, including 3 local recurrences, 3 metastases, and 3 deaths, were seen only in malignant OFMT. IHC results were as follows: S-100 protein (30 of 41, 73%), desmin (15 of 39, 38%), cytokeratin (4 of 35, 11%), EMA (5 of 32, 16%), SMA (2 of 34, 6%), INI-1 (lost in mosaic pattern in 14 of 19, 74%), EAAT4 (31 of 39, 80%), MUC4 (3 of 14, 21%), NFP (8 of 10, 80%) and CD56 (6 of 14, 43%). Gene expression profiling showed typical and malignant OFMTs to cluster together, distinct from schwannian tumors. Proteomic study showed expression of various collagens, S-100 protein, and neuron-related proteins. FISH showed INI-1 deletion in 5 of 7 (71%) cases. We conclude that malignant OFMTs exist and may be recognized by the previously proposed criteria of Folpe and Weiss. Expression of neuron-related markers, in addition to Schwann cell and cartilage-associated markers, suggests a "scrambled" phenotype in OFMTs. Loss of INI-1 or other genes on 22q is likely important in the pathogenesis of these rare tumors.

Ossifying fibromyxoid tumour: a rare soft tissue tumour of intermediate malignancy

Ossifying fibromyxoid tumours (OFTs) are uncommon soft tissue tumours. A 73-year-old male presented with a painless exophytic mass located in the left scapular area which was identified 1 year earlier. An incisional biopsy was performed and microscopic features were compatible with OFT. Radiologic evaluation revealed multiple pulmonary metastasis. Although many cases persue an indolent biologic behaviour, local recurrence and metastasis have been reported and long-term follow-up should be considered.