8th Mar 2021

ICRI CASE OF WEEK

Contributed by- Dr Chaitali Parekh

Consultant Musculoskeletal Interventional Radiologist
Pulse chain of centres, Mumbai
Nutech diagnostic centre, Kalyan

Copyright : Dr Chaitali Parekh

DNB, FRCR(UK)
Fellowship in Musculoskeletal Interventional Radiology

Case History

• 38 year old male with chronic fatigue, muscle
pain, low back pain and stiffness developed
worsening bilateral thigh pains refractory to
medications. No h/o trauma.

• Patient had undergone a battery of
investigations over a period of one year with
gradual worsening of the symptoms

• Blood investigations –

Low phosphorus levels (1.9 mg/dl)
Normal calcium, PTH, ANA, ANCA, ESR, CRP levels
Raised Fibroblast growth factor 23 / FGF 23 (413

RU/ml)
DEXA – Osteoporosis in right femoral neck and

lumbar spine with osteopenia in left femoral neck

ab

What are the findings?

c

d

What are the findings?

e

ab
Anteroposterior (a) and frog leg lateral (b)
radiographs of pelvis with both hips show linear
radiolucencies in bilateral femoral necks consistent
with bilateral femoral neck stress fractures.
Mild coxa vara noted on left side.

Bone window image of CT chest (c) shows healing
right rib stress fracture (black arrow)

c

STIR coronal (d) MRI image shows linear
hypointense signal in bilateral femoral
necks with moderate adjacent marrow
edema (white arrows), consistent with
stress fractures. Mild marrow edema noted
in right inferior pubic ramus (black arrow).
Arrow head shows normal left inferior
pubic ramus

d

Axial T1 (e) MRI image shows linear hypointense
signal in right inferior pubic ramus, consistent
with non displaced fracture

e

What is the working diagnosis?

• Multiple stress fractures with
hypophosphatemia on blood investigations –
diagnosis of Hypophosphatemic Osteomalacia
is considered

f gh

What are the findings and what is the
final diagnosis?

i

f gh

T2 axial (f) and T1 post contrast axial and coronal
(g,i) MRI images show an ill defined T2 iso to mildly
hyperintense soft tissue lesion (black arrow)
adjacent to the adductor and gracilis muscles origin,
with marked post contrast enhancement (white
arrow).
Somatostatin receptor PET CT study with gallium 68
DOTATATE (h) shows avid uptake of the tracer in the
i soft tissue lesion (arrow head).

What is the final diagnosis?

• Phosphaturic mesenchymal tumor with tumor
induced hypophosphatemic osteomalacia and
stress fractures

Discussion

• Phosphaturic mesenchymal tumors are rare tumors with
around 300 cases reported in literature.

• They are mixed connective tissue tumors that cause tumor
induced osteomalacia or rickets by overproduction of
phosphaturic hormone fibroblast growth factor 23 (FGF 23).

• They are usually benign and slow growing.

• These tumors can originate in soft tissues or bone - can occur
in variable odd locations and remain undiagnosed or get
misdiagnosed

• Clinical symptoms
– Vague and long standing symptoms
– Fatigue, generalised weakness
– Muscle and bone pains
– Multiple stress fractures

• Imaging findings –

– Generalised osteopenia

– Multiple stress fractures of different ages

– Diagnosis of the tumor purely on CT or MRI can be difficult
owing to the small size and non specific appearance

– Gallium DOTATATE PET CT and 111In Octreotide scan –
show avid tracer uptake and help in localisation of tumor

• Imaging findings –

– MRI characteristics –
 T1 – hypointense
 T2 – hyperintense
 Marked post contrast enhancement in small tumors
with heterogenous enhancement in large tumors
 Can contain calcification, fat or even vascular flow voids

• Somatostatin receptor PET CT study can aid in diagnosis and
localisation of both soft tissue and bone tumors particularly
smaller ones.

• Raised FGF 23 and lesion biopsy with histopathology can
confirm the diagnosis.

• Delay in the diagnosis due to non specific clinical picture and
blood investigations result in increased morbidity in the
patients from fatigue, myopathies, repeated stress fractures
and increased mortality rates associated with the tumor.

Management

• Management includes wide excision of the tumor. Incomplete
surgical removal of the tumor can result into local recurrence and
rarely metastasis.

• Post surgical removal of the tumor, patient has immediate
improvement in clinical symptoms and normalisation of serum
phosphorus levels with good prognosis.

• Radiofrequency ablation of the tumor is a developing less invasive,
safe modality of treatment, particularly in patients where surgical
resection in difficult due to inaccessible location of tumor or
associated co-morbidities prohibiting surgery

Teaching Points

• Have high index of suspicion - Tumor induced osteomalacia
should be included in the differentials of hypophosphatemic
osteomalacia.

• Correct diagnosis is crucial - Delayed diagnosis can cause
increased morbidity for years, with correct diagnosis and
surgical removal causing immediate clinical improvement.

• Be aware - of this entity and the vague clinical picture
associated with it. Any bone or soft tissue lesions in such
patients should be looked up with suspicion and the patient
should be further worked up with FGF 23 levels and
Somatostatin receptor PET CT (Ga DOTATATE) study.

References

• Shi Z, Deng Y, Li X, Li Y, Cao D, Coossa VS. CT and MR imaging features in phosphaturic mesenchymal
tumor-mixed connective tissue: A case report. Oncol Lett. 2018;15(4):4970-4978.
doi:10.3892/ol.2018.7945

• Broski SM, Folpe AL, Wenger DE. Imaging features of phosphaturic mesenchymal tumors. Skeletal
Radiol. 2019 Jan;48(1):119-127. doi: 10.1007/s00256-018-3014-5. Epub 2018 Jul 9. PMID:
29987349.

• Anke H. Hautmann, Josef Schroeder, Peter Wild, Matthias G. Hautmann, Elisabeth Huber, Patrick
Hoffstetter, Martin Fleck, Christiane Girlich, "Tumor-Induced Osteomalacia: Increased Level of FGF-
23 in a Patient with a Phosphaturic Mesenchymal Tumor at the Tibia Expressing Periostin", Case
Reports in
Endocrinology,vol. 2014, ArticleID 729387, 7 pages, 2014. https://doi.org/10.1155/2014/729387

• Agrawal K, Bhadada S, Mittal BR, Shukla J, Sood A, Bhattacharya A, Bhansali A. Comparison of 18F-
FDG and 68Ga DOTATATE PET/CT in localization of tumor causing oncogenic osteomalacia. (2015)
Clinical nuclear medicine. 40 (1): e6-e10. doi: 10.1097/RLU.0000000000000460

• Mishra SK, Kuchay MS, Sen IB, Garg A, Baijal SS, Mithal A. Successful Management Of Tumor-
Induced Osteomalacia with Radiofrequency Ablation: A Case Series. JBMR Plus. 2019;3(7):e10178.
Published 2019 Feb 28. doi:10.1002/jbm4.10178