A Case Report of Subcutaneous Ossifying Fibromyxoid Tumour of the Back.

Ossifying fibromyxoid tumour (OFMT) is a rare subcutaneous soft tissue neoplasm, with unclear lineage and intermediate differentiation. Typically presenting as a benign growth, however it can recur locally, and malignant variants have been reported. We present an unusual case of OFMT occurring as a subcutaneous mass on the right upper back. A 29-year-old gentleman presented with one-year history of a painless, slowly enlarging mass on his right upper back. He had no relevant medical history, was not on any medications, and had no family history of skin cancer. Physical examination revealed a 25mm x 25mm skin-coloured, stony-hard, well circumscribed mass. The initial clinical diagnosis was a calcified epidermoid cyst. The lesion was excised and sent for histopathology, which revealed well-circumscribed cellular spindle cells with low mitotic index. Immunohistochemistry showed variable S100 positivity. Due to its rarity, the diagnosis was delayed as the biopsy required a second opinion from a tertiary hospital. The final pathological diagnosis confirmed OFMT. This case describes the very rare presentation of OFMT in a dermatology clinic, highlighting the importance of recognising this neoplasm due to its potential for recurrence and metastasis. This unusual case of OFMT broadens the dermatological differential diagnosis for a subcutaneous mass.

Soft tissue sarcoma with ZC3H7B::BCOR fusion in a male mimicking low-grade fibromyxoid sarcoma - A case report.

Diagnosis of soft tissue tumors is often challenging, given the large number of entities, often with non-specific or overlapping morphology. Although morphology still plays an important part in diagnostic process, additional studies including immunohistochemistry and molecular genetics are often needed to arrive at correct diagnosis. We report a case of 61-year-old male with subcutaneous tumor in right hip area, that was surgically removed. The tumor was composed of uniform bland spindle cells in mild to moderately cellular myxoid nodules, with limited areas of collagenization and the diagnosis of low grade fibromyxoid sarcoma was made. The tumor recurred 3 years after the initial diagnosis and the new sample showed a high-grade round cell sarcoma with limited residual low-grade areas and non-specific immunoprofile after extended immunohistochemical work-up. Molecular analysis demonstrated ZC3H7B::BCOR fusion. Sarcomas with ZC3H7B::BCOR fusion occurring outside of uterus are exceedingly rare. A comprehensive review of previously published cases and a short discussion about classification of the entity is provided, together with data about morphology and immunoprofile of the lesions. The case also underscores the necessity of extended work up of soft tissue tumors with unusual immunohistochemical or morphological features in order to accurately assess their biological potential.

Expanding the molecular signatures of malignant ossifying fibromyxoid tumours with two novel gene fusions: PHF1::FOXR1 and PHF1::FOXR2.

AIMS: Ossifying fibromyxoid tumor (OFMT) is a rare enigmatic tumor of uncertain differentiation that can be classified as typical, atypical, and malignant subtypes based on cellularity, nuclear grade, and mitotic activity. The majority of OFMTs, regardless of the risk of malignancy, harbor genetic translocations. We report two malignant OFMTs, including one with evidence of dedifferentiation, with novel genefusions. METHODS AND RESULTS: Case 1 was a 63-year-old male with a dedifferentiated OFMT arising in the right wrist, while case 2 was a 41-year-old male with a malignant OFMT presenting as a posterior mediastinal mass. Case 2 showed multifocal expression with EMA and synaptophysin, while desmin and S100 were absent in both tumors. NGS sequencing studies detected PHF1::FOXR1 and PHF1::FOXR2 gene fusions in cases 1 and 2, respectively. Despite aggressive regimens, both progressed with wide spread metastases resulting in death within six years of diagnosis. CONCLUSIONS: We expand the genetic spectrum of OFMTs with two novel gene fusions, PHF1::FOXR1 and PHF1::FOXR2. These cases confirm the previously reported tendencies for OFMTs with rare variant fusions to demonstrate malignant behavior, unusual morphology, and non-specific immunophenotype.