A huge vulval cyst with iliac lymph node enlargement – A unique presentation of a rare tumor

Q1 – WHAT IS YOUR INTERPRETATION?

1. Angiomyxoma

2. Myxofibrosarcoma

3. Myxoid dermatofibrosarcoma protuberans

4. Myxoid liposarcoma.

Question 1 answer – d-Myxoid liposarcoma.

BRIEF DISCUSSION

Smears made from FNA of the right iliac lymph node showed tissue fragments with myxoid matrix and plexiform vascular network [Figure 1: Arrowhead] surrounded by round to ovoid cells with mild atypia admixed with univacuolated to multivacuolated lipoblasts with scalloped nuclei [Figure 1: Arrow]. A diagnosis of low-grade myxoid liposarcoma (MLS) was made on FNAC. FNAC of the iliac lymph node was followed by removal of the right labial mass which was sent to pathology department for histopathological evaluation. The lesion was a well encapsulated, grayish-white to grayish-brown, lobular mass measuring 8.5 × 5.0 × 4.0 cm [Figure 2].

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Figure 2:

MRI well-defined 10.0 × 10.0 × 5.0 cm right vulval mass showing heterogeneous signal intensity, hypointense on T1 and hyperintense on T2.

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Gross evaluation revealed solid, multilobulated cut surface with grayish-white, fleshy and gelatinous areas with foci of hemorrhage [Figure 3]. Representative sections were submitted for microscopic evaluation. H&E stained sections from labial mass showed nodular lesion with hypocellular and hypercellular areas. Hypocellular areas showed uniform round to oval-shaped cells admixed with variable number of univacuolated to multivacuolated lipoblasts embedded in prominent myxoid stroma, rich in arborizing chicken wire capillary vasculature [Figure 4].

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Figure 3:

Solid, grayish-brown multilobulated mass with grayish-white fleshy and gelatinous areas (original).

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Figure 4:

Hypocellular areas showing round cells admixed with lipoblasts (arrowhead) embedded in prominent myxoid stroma, rich in arborizing, plexiform capillary vasculature (arrow). (H and E, ×400) (original) Inset=lipoblast).

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Extensive grossing was done and then slides were stained with H&E. Sections from labial mass showed nodular lesion with hypocellular and hypercellular areas. Hypocellular areas show uniform round to oval-shaped cells admixed with variable number of univacuolated to multivacuolated lipoblasts embedded in prominent myxoid stroma, rich in arborizing chicken wire capillary vasculature [Figure 4]. Hypercellular areas showed predominantly sheets of round to ovoid cells (approximately 25%) with high nuclear cytoplasmic ratio and absent to scant amount of cytoplasm, favoring a diagnosis of high-grade MLS [Figure 5].

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Figure 5:

Hypercellular areas showing predominantly sheets of round to ovoid cells. (H and E, ×100) (original).

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ADDITIONAL QUIZ QUESTIONS

Q2 – Plexiform blood vessels are frequently seen in all except

1. MLS

2. Superficial angiomyxoma

3. Lipoblastoma

4. Myxofibrosarcoma.

Q3 – Unimultivacuolated cells with scalloping of nuclei are the feature of

1. Foamy macrophage

2. Pseudolipoblast

3. Lipoblast

4. Adipocyte.

Q4 – Most common translocation involving MLS is?

1. t(12;16)(q13;p11)

2. t(7;16)(q33;p11)

3. t(17;22)(q21.3;q13.1)

4. t(11;12)(q23;q15).

ANSWERS TO ADDITIONAL QUESTIONS

Q2 (d); Q3 (c); Q4 (a).

Q2 (d) – Plexiform vessels are thin branching vessels usually seen in MLS, superficial angiomyxoma, and lipoblastoma. Myxofibrosarcomas, meanwhile, show thick walled, curvilinear vessels with perivascular alignment of tumor cells.

Q3 (c) – Criteria for diagnostic lipoblast include – hyperchromatic, indented or sharply scalloped nucleus with lipid-rich droplets in cytoplasm, and an appropriate histological background. Multivacuolated cells distended with hyaluronic acid (pseudolipoblast) can be seen in myxofibrosarcoma.

Q4 (a) – The entire range of myxoid/round cell liposarcoma is genetically tied to recurrent rearrangement of DDIT3 that partners with FUS in >95% of cases with a resulting FUSDDIT3 fusion [t(12;16) (q13;p11)] or partners with EWSR1 in the remaining cases with a resulting EWSR1-DDIT3 fusion [t(12;22) (q13;q12)]. Identification of either the FUS-DDIT3 or EWSR1-DDIT3 transcript is considered both highly sensitive and specific for myxoid/round cell liposarcoma, allowing its distinction from morphologically similar neoplasms.

BRIEF REVIEW OF TOPIC

Vulvar sarcomas account for only 1–3% of all vulvar malignancies and the most frequent primary vulvar sarcoma is leiomyosarcoma.^[1,2] MLS of vulva is very rare and only seven cases are reported in literature till date, to the best of our knowledge [Table 1].^[3-8] MLS is the second most common subtype of liposarcoma harboring translocation (12;16) (q13;p11) which creates a chimeric gene FUS-DDIT3 and it encompasses a spectrum of tumors defined by their degree of lipoblastic differentiation. It is divided into low-grade and high-grade MLS according to the WHO classification proposed in 2013. At one end of the spectrum is low-grade MLS associated with favorable prognosis and, on the other end, is, high-grade MLS, defined as having ≥5% round cell component, considered more aggressive tumor which tends to metastasize.

MLS of vulva can be mistaken clinically as benign because of their rare location and presentation, which can lead to delayed treatment.^[9,10] Like in our case, a clinical diagnosis of vulval cyst was made and patient presented with iliac lymph node metastasis which was reported as low-grade MLS. However, on histopathology of labial mass, we encountered the round cell component as well, thus rendering it as high-grade MLS. Sometimes in hypercellular variant, stroma is less myxoid and capillary network is less prominent leading to erroneous diagnosis of round cell tumor on FNAC. Hence, there is a need for extensive sampling.

Histologically, MLS can be confused with other myxoid tumors more common in the vulva such as aggressive angiomyxomas, botryoid embryonal rhabdomyosarcoma, myxoid dermatofibrosarcoma protuberans, myxofibrosarcoma, and myxoid leiomyosarcoma [Table 2].

SUMMARY

Vulvar MLS is an extremely rare case reported in the literature. The present case marks the seventh reporting of vulval myxoid/ round cell liposarcoma and the first one presenting with iliac lymph node metastasis. Both pathologists and clinicians should be aware of the occurrence of this entity in vulval region to ensure the correct diagnosis and appropriate management of the patient with this potentially curable neoplasm.