ARTICLE
Onychomatricoma is an uncommon benign tumor of the nail matrix that was
first described in 1992 by Baran & Kint [1]. Until now only twenty
cases have been reported in the literature [2-6].
Onychomatricoma has typical clinical features consisting of:
- banded or diffuse thickening of the nail plate along its entire length;
- yellowish discoloration of the involved nail plate that often shows
fine splinter hemorrhages in its proximal portion;
- a tendency toward transverse overcurvature of the nail.
Histologically the tumor is characterised by multiple fibroepithelial
projections that extend into the thickened nail plate. The tumor epithelium
is histologically and histochemically identical to that of the normal
nail matrix and keratinizes without a granular layer.
We report here 3 cases of onychomatricoma, including the first case
in a black patient.
Case reports
Case 1
A 35-year-old white man was referred to us by his dermatologist in October
1998 for the evaluation of a nail lesion that involved the whole nail
plate of the first left toe. The patient reported that the lesion had
appeared about 5 years before. An X-ray of the distal phalanx was normal.
At the clinical examination the nail plate was yellowish, thickened and
transversely overcurved with a slight lateral deviation. Frontal view
of the nail revealed the presence of multiple hollows within the nail
plate (Fig. 1). The nails
of all other toes and fingers were normal. A clinical diagnosis of onychomatricoma
was made and the lesion was surgically removed.
Case 2
A 72-year-old woman consulted us in November 1998 with a 2 year history
of a nail dystrophy involving her left middle finger. She did not remember
any trauma before the onset of the nail abnormalities. Several topical
treatments prescribed by her GP had been ineffective. The nail was thickened
with an atypical yellow discoloration and increased transversal curvature.
The nail surface showed multiple longitudinal striations that, on frontal
view, corresponded to small woodworm-like holes within the nail plate
(Fig. 2). On the basis
of the clinical characteristics mentioned, we made diagnosis of onychomatricoma
and made a complete surgical excision of the tumor.
Case 3
A 40-year-old black man was seen in our Department in January 1999 for
a nail dystrophy of 14 months' duration involving the middle finger of
his left hand. At the clinical examination the nail showed a marked thickening
along its entire length. Several small splinter haemorrhages were visible
in the proximal portion of nail plate. Frontal view of the nail revealed
numerous small hollows of the distal margin (Fig.
3). An X-ray of the finger revealed no bone involvement. Complete
surgical excision of the tumor was performed.
Surgery
After proximal ring anesthesia, the nail plate was removed and the proximal
nail fold was reflected to expose the tumor. The avulsed nail plate showed
the typical wood worm-like holes corresponding to the matrix digitations.
The digitated tumor was completely excised down to the bone and the defect
was closed by direct suture. No recurrences of the tumor were seen at
the follow-up 12 months after surgery.
Histopathology
The histopathological features of the tumor were identical in all 3
patients. Longitudinal sections showed a fibroepithelial filamentous tumor
originating from the nail matrix. The tumor formed projections that were
directed outward and penetrated the corresponding nail plate with a fingerglove
appearance. In the proximal portion the epithelium showed "V-shaped" keratogenous
areas similar to the keratogenous zone of the normal nail matrix. In the
distal portion the fibroepithelial projections were covered by a thin
epithelium resembling nail matrix epithelium (Fig.
4). The tumor stroma consisted of packed eosinophilic collagen
bundles. The nail plate exhibited longitudinally oriented holes corresponding
to the matrix projections. There was no koilocytosis and periodic acid-schiff
(PAS) stain was negative.
Discussion
We report these cases to underline that the clinical features of onychomatricoma
are highly diagnostic as the tumor produces nail abnormalities that are
very characteristic and not seen in other nail disorders. In fact in all
three patients a presumptive diagnosis of onychomatricoma was made by
clinical examination. In particular, the frontal view of the nail showing
a thickened nail plate with multiple hollows strongly suggests this diagnosis.
Rarely, onychomatricoma may arise from the lateral matrix and produce
abnormalities resembling a cutaneous horn [4].
Onychomatricoma more commonly affects fingernails of middle aged individuals.
Males and females are equally affected.
Although some authors believe that onychomatricoma is most likely a
hamartoma, the tumor has never been reported in children. Onychomatricoma
is considered a rare tumor because of the limited number of cases described
in the literature, but it is important to point out that the great majority
of the reported cases (17/20) [1, 2, 4] have been described by Robert
Baran, who first discovered the tumor and is therefore skilled in recognizing
it. We believe that onychomatricoma is possibly not uncommon and we have
diagnosed 3 cases in the last year, including the first case in black
skinned person. The pathology of onychomatricoma is very typical and as
has been pointed out by Baran and Kint, even the gross pathology of the
tumor at the time of excision is unique due to the presence of multiple
matrix digitations and characteristic woodworm-like holes of the corresponding
nail plate [1]. The MR is also typical, sagittal images showing the tumur
core in the matrix area and its projections into the funnel-shaped nail
plate. The center shows a low signal in all images with a peripheral rim
with a signal identical to that of normal epidermis. The tumor digitations
show a higher signal on T2-weighted images due to a mucoid stroma with
high water content [2]. Onychomatricoma is the only nail tumor that originates
from the nail matrix epithelium [7] and primarily produces a deformed
nail plate, all other nail tumors producing secondary nail plate deformities.
As has been clearly described by Haneke "onychomatricoma produces nail
plate alterations that are actively produced by the tumor itself" [3].
Although onychomatricoma is a benign tumor, surgical excision is recommended.
This should include all the matrix proximal to the tumor to avoid recurrences.
Article accepted on 13/9/00
CONCLUSION
1. Baran R, Kint A. Onychomatricoma. Filamentous tufted tumor in the
matrix of a funnel-shaped nail: a new entity (report of three cases).
Br J Dermatol 1992; 126: 510-5.
2. Goettmann S, Drape JL, Baran R, et al. Onychomatricome : deux
nouveaux cas intérêt de la résonance magnétique
nucléaire. Ann Dermatol Venereol 1994; 121: S145.
3. Haneke E, Franken J. Onychomatricoma. Dermatol Surg 1995;
21: 984-7.
4. Perrin C, Goettmann S, Baran R. Onychomatricoma: clinical and histopathologic
findings in 12 cases. J Am Acad Dermatol 1998; 39: 560-4.
5. Raison-Peyron N, Alirezai M, Meunier L, et al. Onychomatricoma:
an unusual cause of nail bleeding. Clin Exp Dermatol 1998; 23:
138.
6. Van Holder C, Dumontier C, Abimelec P. Onychomatricoma. J Hand
Surg 1999; 24: 120-1.
7. Kint A, Baran R, Geerts ML. The onychomatricoma: an electron microscopic
study. J Cutan Pathol 1997; 24: 183-8.
REFERENCES {references} |
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