Enlarging Lump Under the Big Toe Nail - Think of Subungal Exostosis

Diagnosing And Treating A Painful Tumor of the Big Toe

A 28-year-old lady presented with a painful lump on her right big toe.  She noticed this lump over the past 2 months and it has been getting progressively larger.

The nail of her big toe appeared to be lifted off by the lump under the nail. It was painful to press onto the nail of the right big toe.

X-rays showed bony growth (exostosis) of the distal phalanx of the big toe.

Subungal Exostosis | HC Chang Orthopaedic Surgery

Subungal Exostosis | HC Chang Orthopaedic Surgery

Subungal Exostosis | HC Chang Orthopaedic Surgery

Subungal Exostosis | HC Chang Orthopaedic Surgery

What Is the Diagnosis?

The diagnosis is Subungal Exostosis.

In layman’s term, it is a bony projection which arise from the dorsal surface of the last bone of the big toe.

How To Diagnose This Tumour?

Typical clinical signs of this condition are painful raised firm lesions that are located deep to the free edge of the nail. This growth pushes the nail edge and, sometimes, the entire nail upward.

Pain is caused by the enlarging exostoses below and is exacerbated by the shoe pressure above.

The loosened, raised nail plate is typical of this entity.

Is it Cancerous?

No, it is not cancerous.  It is a benign bone tumour.

What Is It Actually?

They are composed of mature bone with a fibrocartilaginous cap.

Lee et al (2007) noted that half of their subungual lesions were actually osteochondromas arising from the proximal part of the distal phalanx and covered with hyaline cartilage organised as in a growth plate.

True exostoses are commonest in young adults with a female predominance.

They mainly occur in the great toe, although they also occur in the lesser toes and fingers.

What is the Treatment?

The tumour usually continues to grow so is best removed when diagnosed.

This can be done under  local  anaesthesia as a day case.

Sometimes the nail fold can be elevated and preserved, but usually it cannot be separated from the lesion and must be sacrificed.

Even with careful excision of the whole lesion, the recurrence rate averages about 10%.

A few patients require removal of so much nail bed that there is significant post-operative nail deformity, so that plastic nail bed reconstruction may be considered.

This picture shows the tumour after the nail was removed:

Subungal Exostosis | HC Chang Orthopaedic Surgery

Subungal Exostosis | HC Chang Orthopaedic Surgery

For more information on Subungal Exostosis or any lumps and bumps of your hands or toes, please contact us at 683 666 36 or email hcchang@ortho.com.sg.

Please visit our website at www.ortho.com.sg

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