California Tumor Tissue Registry
Case of the Month
July, 2005
“An 8 month old girl with tumors on her fingers”
The mother of an 8 month old baby girl discovered nodules involving the left middle and
long fingers of her daughter. They had been present for an unknown period of time.
The tumors were removed and sent for pathologic examination.
The excised specimens were soft tissue based, white-tan, and 1.2 x 1.2 cm and 1.0 x
0.6 cm. The overlying skin appeared uninvolved. Microscopic exam showed poorly
circumscribed masses composed of bundles of uniform dermal fibroblasts interspersed
with a dense eosinophilic stroma (Fig. 1.). The fibroblasts were uniformly monotonous
and frequently had intracytoplasmic, perinuclear eosinophilic inclusions (Fig. 2). The
bodies were variably sized and often were present in a small area of cytoplasmic
clearing at the end of the spindle-shaped nucleus. They were uniformly rounded,
approximating the size of a red blood cell and stained intensely red by Masson’s
trichrome (Fig. 3).
Diagnosis: “Infantile digital fibromatosis (‘inclusion body fibromatosis’)”
Jon Rittenbach and Don Chase
Department of Pathology, Loma Linda University and Medical Center
California Tumor Tissue Registry
Infantile digital fibromatosis (IDF) is a distinct fibrous soft tissue tumor of infancy and
early childhood. Nearly all cases occur before the age of three and there is a slight
female predilection. The tumor usually presents as a small painless nodule or nodules
on the fingers, or less likely on the toes.
Upon excision, IDF is usually firm, white-tan, and homogenous. The overlying skin is not
involved. Microscopically, IDF shows a dermal or subcutaneous proliferation of uniform
fibroblasts surrounded by dense collagenous stroma. The borders are ill-defined.
Interestingly, the tumor characteristically shows eosinophilic intracytoplasmic inclusions
in the fibroblasts. These are small rounded bodies which are generally adjacent to the
nucleus. They are usually sized around 7 microns but may be variable. Masson
trichrome shows them to stain deeply red and electron microscopy show them to be
consistent with actin microfilaments. The most significant negative stains include PAS
and alcian blue.
Despite a local recurrence rate of up to 60%, the overall prognosis is good. Under
careful observation, many of the tumors have been noted to regress spontaneously.
Since there is no evidence of malignant transformation or locally aggressive behavior the
therapeutic regimen is local excision and close follow-up.
While several soft tissue tumors have identical inclusions (generally female reproductive
tract and breast), their location helps in distinguishing them from IDF. Generally, the
CTTR’s Case of the Month
July, 2005
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diagnosis of IDF is dependent upon correlation with tumor location and patient age,
factoring in the presence of intracytoplasmic inclusions.
Suggested Reading:
Falco NA, Upton J. Infantile digital fibromas. J Hand Surg [Am]. 20(6):1014-20:
1995.
Kwaguchi M, Mitsuhashi Y, Hozumi Y, Kondo S. A case of infantile digital
fibromatosis with spontaneous regression. J Dermatol. 25(8):523-6: 1998.
Rimareix F, Bardot J, Andrac L, Vasse D, Galinier P, Magalon G. Infantile digital
fibroma - report on eleven cases. Eur J pedeatr Surg. 7(6):345-8: 1997.
Rosai and Ackerman’s Surgical Pathology, 9th ed. Mosby:St. Louis,
2251-2252, 2004.
Weiss S, Goldblum J. Enzinger and Weiss’s Soft Tissue Tumors, 4th ed. Mosby:
St. Louis, 2002.
Weidner, Cote, Suster, and Weiss. Modern Surgical Pathology. Saunders
1802-1803, 2003.
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