Discussion
Liposarcoma (LS), the tumor of embryonic mesenchymal origin, is the most
common soft tissue sarcomas (STSs), comprising 15% of all STSs. The
usual site of presentation of this tumor is retroperitoneal (45%),
followed by all extremities (24%).
(1) However, it is
uncommon to see it in the head and neck region, particularly in the oral
cavity. In the review of 23 cases of LS of the oral cavity, the tongue
was the preferred site with an incidence of 52%, whereas LS occurred in
the buccal mucosa in 39% of cases, in another series of 18 cases of LS
of the oral cavity and salivary glands.
(2)
As per WHO 2020, LS is classified into four subtypes based on
morphology, viz. 1. Well-differentiated liposarcoma (WDLS)/ Atypical
lipomatous tumor (ALT), 2.Dedifferentiated liposarcoma (DDLS),
3.Myxoidliposarcoma (MLS), and 4.Pleomorphic liposarcoma (PLS).(3)
Different LS variants have varied aggressive potentials because of their
morphologic diversity. DDLS, high-grade MLS, and PLS all show a high
propensity for metastasis, but WDLS does not metastasize without
dedifferentiation, and MLS has a more indolent clinical behavior and a
reduced metastatic potential.
(4)
Well-differentiated liposarcoma (WDLS), also known as Atypicallipomatous
tumor (ALT), is the most common variant accounting for about 40%-45%
of all LA with the peak age of occurrence between 40-60 years.
(5) Though the oral
cavity, specifically the tongue, rarely gets involved by LS, often it is
WDLS when there is involvement (75% of the cases).
(2) As per Moritani
et al., only 33 cases of WDLS/ALT were recorded globally from 1976 to
2008. (6) The
condition often presents as a slowly growing painless mass without
bleeding, dysphagia, dysgeusia, difficulty in articulation, and
paraesthesia of the tongue. On examination, the lesion mainly presents
as a firm or soft, elastic, nodular, and movable yellow-tan mass with
variation in size depending upon the time of presentation.
(2,6–9) Though the
lesion is limited to submucosal at the time of presentation, as in our
case, the cases with mucosal extrusion have also been reported.
(6,7) Lymph nodes are
typically not palpable, although neighboring lymph nodes were palpable
in the case of Nunes et al.
(10)
A lipoma with regressive alterations and an intramuscular lipomais among
the differential diagnoses for WDLS of the tongue. It was the initial
diagnosis in the cases of Moritani et al. and Allon et al.
(6,8) Other
conditions that should be considered in the differential diagnosis are
amyloidosis, myxoma, myxosarcoma, benign fat tumors (hibernoma),
angiolipoma, fibrolipoma, pseudosarcomatous fasciitis, and malignant
histiocytoma. (8,10)
Amyloidosis was a pre-operative clinical diagnosis in the study of Allon
et al., whereas preliminary diagnosis in the study of Dubin et al.
(8,11) Due to the
broad spectrum of differential diagnosis, detailed histopathological
examination is essential for a definite diagnosis.
The new World Health Organization categorization splits WDLS into three
subclasses based on their morphologic characteristics: adipocytic,
sclerosing, and inflammatory. Despite discovering three histologic
variations, these subclasses have little clinical significance.
(1) The tumor is
yellow-tan, lobulated, and often covered by intact mucosa, giving them
the appearance of a lipoma.
(2) But, in contrast
to the lipoma, WDLS is made up of a relatively mature adipocytic
proliferation in which significant variation in cell size is easily
discernible and is admixed with fibrous connective tissues. Here,
adipocyte nuclei are heavily stained in discrete areas, and unusual
multinucleated stromal cells are frequently seen.
(6) It presents with
limited nuclear atypia and few or no lipoblasts.
(12)Lipoblasts, when
present, are vacuolar, multinucleated, or have highly stained nuclei.
(6) It’s vital to
note that the existence of lipoblasts does neither guarantee nor exclude
a diagnosis of liposarcoma.
(13)
Immunohistological markers add to the diagnosis of liposarcoma. WDLS
exhibits vimentin, S100, MDM-2, Ki-67, and CDK4 positivity. However, the
positivity for the spindle cell component of WDLS is still under
dispute. (2,8) The
genes that code for all of these proteins are found on chromosome
12q13–15. These DNA sequences make up the majority of the supernumerary
ring and giant rod chromosomes, which are the cytogenetic hallmarks of
ALTs in around 93% of instances.
The treatment of choice for WDLS is wide surgical excision. Lymph node
dissection depends upon the state of metastasis. Though the prognostic
value of tumor size is unclear, adequate margin excision has great
prognostic importance as the recurrence rate can increase from 17% to
80% due to incomplete removal of the tumor.
(11) Transformation
of WDLS to dedifferentiated type increases the chance of metastasis.
(12) Hence, adequate
margin coverage and close observation after surgery are crucial in WDLS.
Conclusion:
Though well-differentiated liposarcoma of the tongue is rare, it should
always be on the list of differential diagnoses of tongue lesions.
Resecting adequate margin is crucial during the surgical intervention as
margin positivity has a high predilection for recurrence of WDLS.
Similarly, regular follow-up is pre-vital as there is a chance of
recurrence despite it being rare.