Cellular myofibromas with SRF fusions: clinicopathological and molecular study of 3 cases of a rare entity and a potential mimic of sarcoma.

Cellular myofibromas/myopericytomas harboring recurring SRF fusions are recently characterized as rare and diagnostically challenging entities, which can mimic myogenic sarcomas. These tumors belong to the pericytic/perivascular myoid tumor family, which comprises a group of genetically heterogenous and sometimes morphologically overlapping entities. In this series, we describe 3 cases of SRF-rearranged cellular myofibromas/perivascular myoid tumors with a smooth muscle-like phenotype in children. The children ranged from 7 to 16 years of age, and all presented with a painless mass in the extremities, 2 of which were deep-seated. Histologically, the tumors demonstrated a smooth muscle-like morphology and immunophenotype with mild atypia and low-level mitotic activity. Prominent dense collagen deposition and coarse calcification was observed in 2 tumors. RNA sequencing revealed SRF fusions in all cases, with each tumor showing a different 3' partner gene, RELA, NFKBIE, and NCOA3. Of these, NCOA3 has not been reported previously, and this expands the molecular spectrum by identifying a novel fusion partner for SRF. Given that histological features can be worrisome for a myogenic sarcoma, wider awareness of this emerging tumor is valuable to avoid potential misclassification.

Myopericytoma: a rare case of parapharyngeal localization.

This case study presents a 66-year-old man referred to the Otolaryngology and Head and Neck Surgery department due to a one-history of persistent pain in the left posterior cervical region. No abnormalities were detected in the oral and pharyngeal regions during clinical and endoscopic examinations. Subsequently, a magnetic resonance imaging revealed a lesion (14 × 12 × 14 mm) into the left parapharyngeal space, with high signal intensity on T2-weighted images, enhancement after contrast medium, restricted signal on diffusion weighted imaging and high vascularization on perfusion MRI. The histological examination of the lesion led to a diagnosis of myopericitoma. Post-surgery, no adjuvant therapy was administered. Myopericytomas are rare soft-tissue benign neoplasms, predominantly reported in extremities, with a limited number of cases in the head and neck region and almost never described in the literature with elective localization in the parapharyngeal space.