Avoidance of surgery for head and neck infantile myofibromatosis using imatinib monotherapy

Infantile Myofibromatosis With Cutaneous, Visceral, and CNS Involvement: A Multimodal Approach to Therapy

BACKGROUND

Infantile myofibromatosis (IM) is a rare benign tumor of infancy. Cases with solitary and multicentric disease usually spontaneously regress, but multicentric disease with visceral involvement carries a poor prognosis. Few cases of multicentric disease with central nervous system (CNS) involvement have been reported, and none report survival.

OBSERVATIONS

We present a newborn with multicentric IM with cutaneous, visceral, and CNS involvement. She was treated with vinblastine, methotrexate, and the novel addition of intrathecal methotrexate with treatment response after 1 year of therapy.

CONCLUSIONS

Multicentric IM with CNS involvement can be successfully treated with a multimodal approach of chemotherapy with the addition of intrathecal methotrexate and surgery.

High-Grade Sarcomas with Myogenic Differentiation Harboring Hotspot PDGFRB Mutations

PDGFRB-activating mutations have been reported in pediatric myofibroma and myofibromatosis. However, recurrent gain-of-function PDGFRB mutations have not been documented in sarcomas with myogenic differentiation. Driven by occasional sarcomas harboring PDGFRB mutations, we investigated their prevalence and clinicopathologic and genomic features in a large cohort of sarcomas. An institutional targeted DNA next-generation sequencing database was searched for sarcomas with myogenic differentiation harboring hotspot PDGFRB gene alterations. Among 3300 patients with sarcomas, 21 (0.6%) patients were identified (17 women, 4 men) with an age range of 35 to 88 years. The site distribution included 13 gynecologic tract (12 uteri, 1 vagina), 4 bone and soft tissue, and 4 viscera. All except 1 were high grade. Most patients were diagnosed as sarcomas with myogenic differentiation based on partial staining for 1 or more muscle markers, whereas 6 were labeled as leiomyosarcoma (LMS). Most tumors showed monomorphic spindle morphology, with either heterogeneous features of myofibroblastic and smooth muscle differentiation or an undifferentiated phenotype. Hormone receptors were negative in all uterine cases. PDGFRB immunostaining in all cases tested was strong and diffuse, whereas PDGFRA was negative/focal. The most frequent PDGFRB mutations were exon 12 (43%), exon 14 (N666K/S/T) (38%), and exon 18 (D850Y/H/V or insertion/deletion) (19%). The most frequent co-existing genetic alterations (26% to 37%) occurred in CDKN2A/B, TP53, TERT, and MED12. Moreover, PDGFRB-mutant sarcomas had an overall distinct genomic landscape compared with both uterine and soft tissue LMS control groups. These tumors were associated with a highly aggressive clinical course, with frequent distant metastases (81%) and death (76%), regardless of anatomic location, and worse overall survival compared with the 2 LMS control groups. This is the first study documenting recurrent hotspot PDGFRB alterations in high-grade sarcomas, which show a predilection for uterine location and myogenic differentiation that fall short of the diagnostic criteria for LMS. Further studies are needed to investigate the therapeutic potential of kinase inhibitors in this group of tumors.

A Recurrent Cheek Mass

Solitary infantile myofibroma is a benign fibrous tumor occurring in early childhood. Although rare, it is the most common benign fibrous tumor of infancy. The clinical course of the disease is almost uniformly good since most tumors regress spontaneously. When indicated, conservative surgical excision is the treatment of choice, with a low recurrence rate. We present a case of solitary infantile myofibroma that recurred after three attempts of surgical excision, questioning the reported recurrence rate and the standard of care in recurrent solitary infantile myofibroma.