The myxoid presentation of this tumour led to the consideration of a low-grade fibromyxoid sarcoma
(LGFMS), but the immunophenotypic profile ultimately supported the diagnosis of a perineurioma.
It shares some overlapping features with other infiltrate tumors, such as desmoid-type fibromatosis, neurofibroma, and low-grade fibromyxoid sarcoma
. The misdiagnosis may cause unnecessary surgical overtreatment, especially for those involving bone.
(%) Head and neck 11 (15) Intra-abdomen 30 (40) Retroperitoneum 15 (20) Lung 35 (47) Liver 22 (29) Bone 18 (24) Lymph node 16 (21) Others 29 (39) Maximum length Median (cm) 5.3 (0-21.7) >5 cm 40 (53) Pretreatment Operation 49 (65) Radiation 21 (28) Chemotherapy 8 (11) None 18 (24) Histopathology type Leiomyosarcoma 17 (23) Liposarcoma 15 (20) Spindle cell sarcoma, NOS 14 (19) Pleomorphic sarcoma 6 (8) Synovial sarcoma 5 (7) Others * 18 (24) * Others include angiosarcoma, undifferentiated pleomorphic sarcoma, solitary fibrous tumor, low-grade fibromyxoid sarcoma
, malignant peripheral nerve sheath tumor, breast phyllodes tumor, round cell sarcoma with CIC rearrangement, neuroblastoma, malignant extrarenal rhabdoid tumor, and myxofibrosarcoma.
The most distinctive immunophenotype of SEF is the expression of mucin 4 (MUC4) (up to 70% of cases), similar to that in low-grade fibromyxoid sarcoma
, while staining for cytokeratins is typically negative.
Owing to the bland morphology and the abundant myxoid matrix, low-grade fibromyxoid sarcoma
has to be considered.
The patient underwent left lower-lobe resection; pathology on a section of the lingula revealed a low-grade fibromyxoid sarcoma
consistent with metastatic disease.
Microscopic examination of an office punch biopsy of the mass showed findings consistent with a low-grade fibromyxoid sarcoma
. A radical left hemivulvectomy with left inguinal lymphadenectomy was performed without complication.
It is important to be aware of this lesion in order to not misdiagnose it as other clinically more aggressive neoplasms such as myxoid liposarcoma and low-grade fibromyxoid sarcoma
. More studies including molecular testing for 13q deletion and NAB2STAT6 fusion  in cases of DFML would help to accurately identify the nature of this neoplasm.
Low-grade fibromyxoid sarcoma
(LGFMS) is characterized by its relatively benign histological appearance with spindle cells in a whorling pattern, as well as collagenized and myxoid areas [1,2].
(9) Additionally, a subset is positive for the FUS-CREB3L2 translocation present in low-grade fibromyxoid sarcoma
MUC4 is a useful marker for low-grade fibromyxoid sarcoma
(LGFMS) and sclerosing epithelioid fibrosarcoma (SEF; Figure 5).
The differential diagnosis in this morphologic category include entities such as low-grade fibromyxoid sarcoma
, myxoma, myxofibrosarcoma, and myxoid liposarcoma (Table 2; Figure 2, e and f), which all have myxoid stroma, lack of a characteristic immunohistochemical profile, and (with the exception of examples of myxofibrosarcoma) minimal/mild to no cytologic atypia.