Dr L. Govender

ABSTRACT

We report a case of soft tissue tumour of the fetal thigh detected prenatally. A uniformly inhomogeneous mass measuring 3cm x 4cm x 6cm on the inner aspect of the fetal right thigh was detected in a 36 year old woman in the 30^th week of her first pregnancy. Colour Doppler demonstrated a vascular pedicle that may represent “feeder vessels” connected to the mass. No other anomalies were detected. Our differential for this soft tissue tumour included sarcoma, haemangioma and congenital myofibromatosis. The pregnancy continued uneventfully and a 2.6kg baby (otherwise well) delivered by C-section. Postnatal imaging was suggestive of a haemangioma and this was confirmed histologically. The classification, management and prognosis of this rare finding is highlighted.

INTRODUCTION

The prenatal diagnosis of fetal tumours by ultrasound has been described only in the last two decades. Although fetal tumours are rare, prenatal detection plays an important role in the understanding of the natural history and pathophysiology, which may be associated with serious illness or even death in the fetal or neonatal period. Hence, prenatal diagnosis of fetal tumours has significant implications on the well being of the mother and fetus, as well as perinatal and neonatal outcome.

THE CASE:

We report on a case of a soft tissue swelling of the fetal right thigh. A 36 year old primigravid was referred at 30 weeks gestation with an ultrasound finding of an enlarged fetal thigh. The patient initially presented to her obstetrician at 23 weeks gestation. Having booked late, prenatal screening for chromosomal abnormality was not done. She was otherwise well and the pregnancy was conceived spontaneously. Her booking blood tests were normal and screen for Diabetes was negative.

At her follow up visit 4 weeks later it was noted on ultrasound that the fetal right thigh appeared swollen. At our unit we confirmed the soft tissue swelling of fetal right thigh. A uniformly inhomogeneous mass measuring 3cm x 4cm x 6cm was measured on the inner aspect of the fetal right thigh (figure 1). On colour Doppler, a vascular pedicle that may represent the “feeder-vessels” appeared to connect to the mass. The fetal pelvis and buttock appeared normal. A normal bladder and normal female genitalia were identified. The sacrococcygeal spine was intact. The right femoral bone, although laterally displaced, appeared normal in its entirety and measurement corresponded to gestational age. The right knee, leg and foot appeared normal. The left lower limbs appeared completely normal. Normal limb movements were observed.

The rest of the fetal anatomy including echocardiography was unremarkable. There were no markers of aneuploidy seen or evidence of hydrops. The liquor volume was upper normal with AFI = 20. A normal 3-vessel cord was identified and the umbilical artery Doppler was normal. Our differential diagnosis for this soft tissue tumour of the fetal thigh included: sarcoma (rhabdomyosarcoma, fibrosarcoma), haemangioma or congenital myofibromatosis.

The couple were informed and counselled on the likelihood of their unborn child having a tumour of the right thigh. They were made aware that the exact nature of this swelling cannot be precisely detected on the prenatal scans and hence the difficulty in accurately assessing prognosis. A multidisciplinary team was involved in the management. An MRI confirmed the soft tissue swelling and the most likely diagnosis was a sarcoma of the right fetal thigh. The couple were offered rapid karyotyping with possible ultrasound guided fetal muscle biopsy at the same settings, but they declined any form of invasive testing. . The interim plan was expectant management with standard obstetric care and for delivery at term. At elective caesarean section at 37 weeks gestation, a 2.6 kg infant with good Apgar scores was delivered. A large tumour mass of the right thigh of the baby was present at birth (figure 2). Postnatal imaging of the right thigh was suggestive of haemangioma and large feeder vessels were identified. The baby is currently being managed in conjunction with the Paediatric surgeons with view to embolisation depending on technical feasibility of the tumour mass and / or a later surgical excision.

LITERATURE REVIEW OF FETAL THIGH TUMORS

A literature search has revealed a sparsity of information regarding prenatal diagnosis and management of soft tissue tumours of the thigh. As recent as the past 2 decades only, a medline search revealed 3 case reports of prenatally diagnosed haemangiomas of the fetal thigh^{1,
2, 3}, one case report on lymphangiohaemangioma of the fetal thigh⁴ and one case report on congenital fibrosarcoma of the fetal thigh⁵. Furthermore a formal classification for fetal tumours does not exist. Meizner et al. (2000)⁶, have described tumours according to their location on the body e.g. head and neck, face, abdomen and retroperitoneum, skin, genitalia, sacrococcygeal region as well as tumours of the extremities. A differential for tumours of the extremities include: (i) vascular haematosis; (ii) haemangioma; (iii) lymphangioma; (iv) sarcomas⁷.

The sonographic diagnostic approach for diagnosing fetal tumours in-utero is based on 3 sets of ultrasound signs viz. general, organ specific and tumour specific signs⁶.

Polyhydramnios is an important general sign for fetal tumours, occurring in about 50% of cases. Apart from ultrasound, imaging techniques such as MRI in the third trimester may be a useful alternate method. Rapid karoytyping should be evaluated in all cases of suspected fetal tumours, since malignant tumours can acquire chromosome changes⁶. Fetal tissue biopsy may be considered when ultrasound diagnosis is uncertain and histology will provide the ultimate diagnosis⁶.

The prognosis for fetal tumours rely on factors such as extent of tumour involvement of other organs, associated mechanical problems and proximity to vital organs or structures. Each case of suspected fetal tumour should involve a multidisciplinary team capable of dealing with such tumours. Gestational age at diagnosis of a fetal tumour should be taken into consideration. Parents should be given the option of termination of pregnancy if the tumour is detected before 24 weeks gestation even though in the absence of other life-threatening anomalies, this option may pose an ethical dilemma when counselling parents. In the case of continuing pregnancy, the risk of preterm delivery should be weighted against the need for urgent surgical intervention or relief of vitally compressed structures. The delivery should be at a tertiary hospital.

Although not a common occurrence and a definitive diagnosis usually confirmed postnatally, prenatal detection of fetal tumours will also assure parents the best and most appropriate treatment for their unborn baby. Furthermore, prenatal detection of fetal tumours will alert the obstetrician and the multidisciplinary team of possible problems during pregnancy, labour and immediate postnatal period.

References

Suma V, Marini A, Gamba PG, Luzzatto C. Giant Hemangioma of the Thigh: Prenatal Sonographic Diagnosis. J Clin Ultrasound 18 (1990) 421-424.
Gonçalves LF, Pereira ET, Parente LM, Vitorello DA, Barbosa UC, Saab Neto JA. Cutaneous hemangioma of the thigh: prenatal diagnosis. Ultrasound Obstet. Gynecol. 9 (1997) 128-130.
Sheiner E, Gohar J, Mazor M. Prenatal diagnosis of giant hemangioma of the thigh. Int J Gynecol Obstet 67 (1999) 175-176.
Gonçalves LF, Rojas MV, Vitorello D, Pereira ET, Pereima M, Saab Neto JA. Klippel-Trenaunay-Weber syndrome presenting as massive lymphangiohemangioma of the thigh: prenatal diagnosis. Ultrasound Obstet. Gynecol. 15 (2000) 537-541.
Tadmor OP, Ariel I, Rabinowitz R, Ne׳eman Z, Stark M, Newman M, Yagel S, Diamant YZ. Prenatal sonographic appearance of congenital fibrosarcoma. J Clin Ultrasound 26(5) (1998) 276-279.

Figure 1 Sonographic images of the fetal thigh at 30 weeks (left image) and 36 weeks (right image) demonstrating the soft tissue swelling in the medial aspect. (RT = right thigh; LT = left thigh).

Figure 2 Day 3 Postnatal image of swollen fetal right thigh