Keywords
Fibromyxoid - ossifying - tumor - tongue
Introduction
Ossifying fibromyxoid tumors (OFMTs) are rare musculoskeletal tumors of uncertain
malignant potential, initially reported by Enzinger et al.[1] Most OFMTs arise from the subcutaneous tissue, skeletal muscles of extremities,
trunk, or head-and-neck region. OFMTs frequently present in the middle-aged adults
as a painless, slow-growing, and well-defined mass.[1] The masses are usually <10 cm in diameter. In the oral cavity, most OFMTs range
from 10 mm to 60 mm. OFMTs are usually benign, but atypical and malignant OFMTs have
been described by Folpe and Weiss, which show high cellularity and/or high mitotic
count with a highly aggressive course.[2]
We are presenting an unusual case of malignant OFMT of the tongue. It is the second
case of malignant OFMT tongue, to the best of our knowledge, the first case of malignant
OFMT of the tongue was described by Ohta et al. in 2013.[3]
Case Report
A 35-year-old female presented with a painless firm mass at the right lateral border
of the tongue for 1½ months, rapidly increasing in size up to 3 cm. The mass was biopsied
thrice with inconclusive reports from different centers. Finally, wide local excision
was performed and sent for histopathological examination in our department. Grossly,
the tumor was circumscribed gray-brown soft-tissue piece measuring 3 cm × 2.5 cm ×
1 cm. Cut section was solid and gray white in color [Figure 1]. Microscopic examination showed the presence of central areas of osteoid and woven
bone with spindle cell tumor arranged in loose and compact fascicles having round-oval
nucleus showing moderate nuclear pleomorphism with prominent nucleolus and atypical
mitoses and many giant cells. On performing immunohistochemical (IHC) analysis, the
tumor cells showed diffuse positivity for vimentin and S100 and negative for cytokeratin
and P63 [Figure 2]. A final diagnosis of malignant OFMT (high grade with 5 mitoses/10 HPF) was made.
Figure 1: Gross examination: On cut section of the resected mass, encapsulated gray-brown
mass from lateral border of the tongue
Figure 2: (a) H and E sections, Low power (×10) showing spindle-to-oval cells with
indistinct cytoplasm arranged in fascicles and fibromyxoid matrix. Note osteoid formation
on lower left end. (b) Atypical mitosis with nuclear pleomorphism seen on high-power
view (×40). Immunohistochemical markers: (c) S100 (C + N) and (d) Vimentin (C) positivity,
(e) cytokeratin (C) and (f) P63(N) negativity
Discussion
Malignant OFMT of the tongue is an unusual site for a rare tumor. In 1989, a series
of 59 cases from the Armed Forces Institute of Pathology revealed the benign nature
of majority of cases. However, few cases may recur locally and metastasize.[1]
Folpe and Weiss found that recurrence and metastatic rate of OFMTs were 17% and 5%,
respectively, and they considered these lesions to be of borderline malignancy.[2] In their study of 70 cases of OFMTs, 29% of cases showed typical features and 64%
of cases showed mixed features of typical and atypical. The tumors occurred as subcutaneous
or deeply seated masses in the trunk and proximal extremities. After the analysis,
they concluded that tumors with a high nuclear grade, increased cellularity and mitotic
count >2/50 HPF should be regarded as sarcoma with a significant potential for metastasis,
but after follow-up, six of ten cases had metastatic disease, described later as atypical
OFMTs. They had atypical histological features including high nuclear grade, increased
cellularity, and increased mitotic activity. The present case also has an increased
cellularity, moderate nuclear atypia, and increased mitotic activity with morphological
features of OFMTs. The patient had a history of recurrence at the lateral border of
the tongue, which is a very unusual site of OFMTs.
Williams et al. reported that one of nine head-and-neck OFMTs have malignant behavior.[4] In 1995, Kilpatrick et al. reported 6 atypical/malignant OFMTs. On follow-up, some cases developed recurrence
and few presented with distant metastasis.[5] Graham et al. also suggested the term “malignant OFMT” using IHC and gene expression profiling.[6]
Ohta et al. reported the recurrence of malignant OFMT of the tongue. Recurrent tumor was composed
of closely packed cells positive for vimentin and S-100 proliferating in a nodular
fashion; tumor cells were arranged in a diffuse or cord-like manner with high cellularity
and mitotic activity within an abundant fibromyxoid matrix, along with a small amount
of metaplastic ossification, corresponding to the histopathological characteristic
of OFMT. The present case also has similar morphological and IHC findings.[3]
The line of differentiation of OFMT is still in doubt. Some literature suggested a
Schwannian or neuronal differentiation.[7] While Enzinger et al. proposed its cartilaginous or myoepithelial differentiation. Recently, according
to Gebre-Medhin et al., the arrangement of PHF1 gene in these tumors suggests that OFMTs are translocation
associated showing scrambled phenotype which is originally hypothesized by Folpe and
Weiss in 2003.[8]
A variety of lesions were considered in the differential diagnosis, including sarcomatoid
carcinoma, epithelioid smooth muscle tumors, epithelioid nerve sheath tumors, myoepithelioma/myoepithelial
carcinoma, and ectomesenchymal chondromyxoid tumors of the tongue. Because of their
overlapping IHC markers expression, they were excluded on the basis of clinical, radiological,
and histological findings. Peripheral bone formation is a pathognomonic feature of
OFMT, aneurysmal bone cyst of the soft tissue, and myositis ossificans. The above-mentioned
differential diagnosis does not have peripheral bone formation and they have ossification
within the tumor. A final diagnosis of malignant OFMT is made. Because of the possibility
of recurrence, understanding OFMT in the tongue with exclusion of other differential
diagnoses is essential for proper and prompt management.
