Plexiform fibromyxoma: Review of rare mesenchymal gastric neoplasm and its differential diagnosis

Abstract

Plexiform fibromyxoma (PF) is a very rare mesenchymal neoplasm of the stomach that was first described in 2007 and was officially recognized as a subtype of gastric mesenchymal neoplasm by World Health Organization (WHO) in 2010. Histologically, PF is characterized by a plexiform growth of bland spindle to ovoid cells embedded in a myxoid stroma that is rich in small vessels. The lesion is usually paucicellular. While mucosal and vascular invasion have been documented, no metastasis or malignant transformation has been reported. Its pathogenesis is largely unknown and defining molecular alterations are not currently available. There are other mesenchymal tumors arising in the gastrointestinal tract that need to be differentiated from PF given their differing biologic behaviors and malignant potential. Histologic mimics with spindle cells include gastrointestinal stromal tumor, smooth muscle tumor, and nerve sheath tumor. Histologic mimics with myxoid stroma include myxoma and aggressive angiomyxoma. Molecular alterations that have been described in a subset of PF may be seen in gastroblastoma and malignant epithelioid tumor with glioma-associated oncogene homologue 1 ( GLI1 ) rearrangement. The recent increase in publications on PF reflects growing recognition of this entity with expansion of clinical and pathologic findings in these cases. Herein we provide a review of PF in comparison to other mesenchymal tumors with histologic and molecular resemblance to raise the awareness of this enigmatic neoplasm. Also, we highlight the challenges pathologists face when the sample is small, or such rare entity is encountered intraoperatively.

Spontaneous hemoperitoneum as a rare presentation of gastric lesions: Two case reports

“…Most common symptoms are abdominal pain/discomfort, fullness, nausea and vomiting, followed by symptoms of blood loss (bleeding, syncope, anemia). To our knowledge, it is the first case of PF presenting as hemoperitoneum [8] .…”

“…PF is a very rare mesenchymal neoplasm of the stomach that was first described in 2007 and was officially recognized as a subtype of gastric mesenchymal neoplasm by World Health Organization in 2010. To date, a total of 130 PF cases have been reported in the English literature [8] .…”

Gastric Plexiform Fibromyxoma in Children - A New Case Report and Review of Pediatric Literature

“…Mitoses are rare and cells have no signs of atypia. Vascular invasion is reported in literature suggesting that intravascular tumour spread is possible [13]. Immunohistochemically, a diffuse positive reaction to vimentin, Smooth Muscle Actin (SMA) and muscle specific actin (MSA) is founded, indicating the fibroblastic, myofibroblastic and smooth muscle cell natures of PF [11].…”

“…As PF displays common clinical and radiological findings with other mesenchymal tumours like GISTs, neuronal tumours, smooth muscle tumours and fibroblastic tumours [3], pre-operative diagnosis is unreliable. Indeed, histological features are typical and show a plexiform growth pattern with multiple nodules with spindle-cells embedded in an abundant myxoid or fibromyxoid stroma [13]. Mitoses are rare and cells have no signs of atypia.…”

“…Regardless patients' age, PF displays a benign clinical behaviour and no recurrence, metastasis or tumour-related deaths have been reported in literature so far. The positive prognosis is also confirmed by the absence or low degree of atypia and low mitotic index (Ki67), with surgery being limited only to tumour excision with no regional lymphadenectomy performed [13]. However, due to scanty literature with short follow-up, it is not possible to exclude with certainty that the tumour could express malignant features in the long run.…”