0
We're unable to sign you in at this time. Please try again in a few minutes.
Retry
We were able to sign you in, but your subscription(s) could not be found. Please try again in a few minutes.
Retry
There may be a problem with your account. Please contact the AMA Service Center to resolve this issue.
Contact the AMA Service Center:
Telephone: 1 (800) 262-2350 or 1 (312) 670-7827  *   Email: subscriptions@jamanetwork.com
Error Message ......
Observation |

Onychocytic Matricoma: A New, Important Nail-Unit Tumor Mistaken for a Foreign Body FREE

Karolyn A. Wanat, MD1; Erika Reid, MD1; Adam I. Rubin, MD1
[+] Author Affiliations
1Department of Dermatology at the Hospital of the University of Pennsylvania, Philadelphia
JAMA Dermatol. 2014;150(3):335-337. doi:10.1001/jamadermatol.2013.6358.
Text Size: A A A
Published online

Onychocytic matricoma (OCM) is a benign acanthoma of the nail unit that presents with localized thickening of the nail plate and melanonychia.1 This newly described entity has suggestive clinical features and distinctive histopathologic changes.

REPORT OF A CASE

A man in his 40s presented with a history of traumatic injury to the nail unit, after which he noted a dark line under the nail, which he assumed to be a splinter. It persisted for 3 years without any notable change. The patient reported removing portions of it when he would clip the nail back.

Physical examination demonstrated a 2-mm-wide black longitudinal streak extending to the distal lunula with localized nail plate thickening on the right second digit (Figure 1A and B). Dermatoscopic findings were consistent with a foreign body under the nail (Figure 1C and D). Nail clippings of the nail plate were performed to sample the distal portion of the lesion and demonstrated parakeratosis associated with pigmentation.

Place holder to copy figure label and caption
Figure 1.
Clinical and Dermatoscopic Findings

A, On the right second digit, there was a black longitudinal streak that involved almost the entire length of the nail unit, but stopped at the proximal nail fold. B, Localized nail-plate thickening also was observed. C, Dermatoscopic findings highlighted the pigmentation. D, The localized thickening simulated a foreign body.

Graphic Jump Location

A partial central nail plate avulsion was performed, as was a longitudinal excisional biopsy. Histopathologic analysis revealed a benign, pigmented epithelial proliferation of the nail matrix epithelium associated with a longitudinal collection of pigmented cells with retained nuclei below the overlying nail plate (thickened keratogenous zone) (Figure 2). Fontana staining highlighted the melanin-derived pigmentation in the epithelium and nail plate. MART-1 staining did not highlight any melanocytes. Findings of periodic acid–Schiff staining and human papilloma viral immunohistochemical analysis were negative. Based on these histopathologic findings, a diagnosis of a pigmented onychocytic matricoma with keratogenous features was made. The patient underwent definitive excision of the lesion, and at 1-year follow-up, there was no recurrence.

Place holder to copy figure label and caption
Figure 2.
Histopathologic Findings

Excisional biopsy highlighted a proliferation of the nail matrix epithelium with pigmented cells and a thickened keratogenous zone on high power (hematoxylin-eosin, original magnification ×200).

Graphic Jump Location

DISCUSSION

We report a case that highlights the recently described and distinct tumor of the nail matrix, OCM. This lesion presents clinically as a localized thickening of the nail plate often with an associated longitudinal melanonychia that might simulate a foreign body, as in this case. Microscopically, it is a benign acanthoma of the nail unit with key characteristics that include endokeratinization and concentrically arranged nests of prekeratogenous and keratogenous cells with variation in the prekeratogenous and keratogenous components depending on the histopathologic subtypes (acanthotic, papillomatous, or keratogenous with retarded maturation).1 In addition, OCM can be classified by pigmentation (pigmented, melanocytic, or hypopigmented/nonpigmented variants).1,2 Our case would be classified as a keratogenous and pigmented OCM, based on the prominent keratogenous zone and pigmentation observed (Figure 2).

Various benign and malignant tumors, including melanoma, as well as lesions caused by the presence of foreign bodies can present as longitudinal melanonychia with a thickened nail plate. Detailed histopathologic analysis is needed to establish a diagnosis. Among the benign lesions that can present as longitudinal melanonychia, onychopapilloma is a nail-bed tumor characterized by acanthosis in the presence of nail-bed papillomatosis.3 Onychocytic matricoma differs by its location in the nail matrix as opposed to nail bed.

Within the nail matrix, onychomatricoma is the most common benign lesion comprising both epithelial strands and a CD34+ fibrous and cellular stroma.4 Clinically, onychomatricomas can present with longitudinal melanonychia and nail plate thickening but have a distinct honeycomb pattern after nail clipping.4,5 Onychocytic matricoma is microscopically distinct as a purely epithelial tumor, lacking the combined fibroepithelial components found in an onychomatricoma.

The most difficult differentiation may be between subungual seborrheic keratoses and OCM; the presence of prekeratogenous and keratogenous zones and thickened nail plate in OCM may help distinguish these entities.6 However, considering these both on a benign spectrum of nail-unit acanthomas may be the best technique for classification.2

We report herein a case of OCM that clinically presented as a pigmented foreign body to make clinicians aware of this benign matrical tumor and to add a new entity to the differential diagnosis of a foreign body in the nail unit.

ARTICLE INFORMATION

Corresponding Author: Adam I. Rubin, MD, Department of Dermatology, Hospital of the University of Pennsylvania, 3600 Spruce St, 2 Maloney, Philadelphia, PA 19104 (Adam.Rubin@uphs.upenn.edu).

Published Online: February 5, 2014. doi:10.1001/jamadermatol.2013.6358.

Conflict of Interest Disclosures: None reported.

Additional Information: Dr Wanat is now with the Department of Dermatology, University of Iowa, Iowa City.

REFERENCES

Perrin  C, Cannata  GE, Bossard  C, Grill  JM, Ambrossetti  D, Michiels  JF.  Onychocytic matricoma presenting as pachymelanonychia longitudinal: a new entity (report of five cases). Am J Dermatopathol. 2012;34(1):54-59.
PubMed   |  Link to Article
Spaccarelli  N, Wanat  KA, Miller  CJ, Rubin  AI.  Hypopigmented onychocytic matricoma as a clinical mimic of onychomatricoma: clinical, intraoperative and histopathologic correlations. J Cutan Pathol. 2013;40(6):591-594.
PubMed   |  Link to Article
Miteva  M, Fanti  PA, Romanelli  P, Zaiac  M, Tosti  A.  Onychopapilloma presenting as longitudinal melanonychia. J Am Acad Dermatol. 2012;66(6):e242-e243.
PubMed   |  Link to Article
Durrant  MN, Palla  BA, Binder  SW.  Onychomatricoma: a case report with literature review. Foot Ankle Spec. 2012;5(1):41-44.
PubMed   |  Link to Article
Miteva  M, de Farias  DC, Zaiac  M, Romanelli  P, Tosti  A.  Nail clipping diagnosis of onychomatricoma. Arch Dermatol. 2011;147(9):1117-1118.
PubMed   |  Link to Article
Okamoto  O, Ishikawa  K, Kai  Y, Yokoyama  S, Fujiwara  S.  Longitudinal melanonychia caused by unusual subungual keratosis. J Dermatol. 2012;39(11):930-931.
PubMed   |  Link to Article

Figures

Place holder to copy figure label and caption
Figure 1.
Clinical and Dermatoscopic Findings

A, On the right second digit, there was a black longitudinal streak that involved almost the entire length of the nail unit, but stopped at the proximal nail fold. B, Localized nail-plate thickening also was observed. C, Dermatoscopic findings highlighted the pigmentation. D, The localized thickening simulated a foreign body.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 2.
Histopathologic Findings

Excisional biopsy highlighted a proliferation of the nail matrix epithelium with pigmented cells and a thickened keratogenous zone on high power (hematoxylin-eosin, original magnification ×200).

Graphic Jump Location

Tables

References

Perrin  C, Cannata  GE, Bossard  C, Grill  JM, Ambrossetti  D, Michiels  JF.  Onychocytic matricoma presenting as pachymelanonychia longitudinal: a new entity (report of five cases). Am J Dermatopathol. 2012;34(1):54-59.
PubMed   |  Link to Article
Spaccarelli  N, Wanat  KA, Miller  CJ, Rubin  AI.  Hypopigmented onychocytic matricoma as a clinical mimic of onychomatricoma: clinical, intraoperative and histopathologic correlations. J Cutan Pathol. 2013;40(6):591-594.
PubMed   |  Link to Article
Miteva  M, Fanti  PA, Romanelli  P, Zaiac  M, Tosti  A.  Onychopapilloma presenting as longitudinal melanonychia. J Am Acad Dermatol. 2012;66(6):e242-e243.
PubMed   |  Link to Article
Durrant  MN, Palla  BA, Binder  SW.  Onychomatricoma: a case report with literature review. Foot Ankle Spec. 2012;5(1):41-44.
PubMed   |  Link to Article
Miteva  M, de Farias  DC, Zaiac  M, Romanelli  P, Tosti  A.  Nail clipping diagnosis of onychomatricoma. Arch Dermatol. 2011;147(9):1117-1118.
PubMed   |  Link to Article
Okamoto  O, Ishikawa  K, Kai  Y, Yokoyama  S, Fujiwara  S.  Longitudinal melanonychia caused by unusual subungual keratosis. J Dermatol. 2012;39(11):930-931.
PubMed   |  Link to Article

Correspondence

CME
Also Meets CME requirements for:
Browse CME for all U.S. States
Accreditation Information
The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
Note: You must get at least of the answers correct to pass this quiz.
Please click the checkbox indicating that you have read the full article in order to submit your answers.
Your answers have been saved for later.
You have not filled in all the answers to complete this quiz
The following questions were not answered:
Sorry, you have unsuccessfully completed this CME quiz with a score of
The following questions were not answered correctly:
Commitment to Change (optional):
Indicate what change(s) you will implement in your practice, if any, based on this CME course.
Your quiz results:
The filled radio buttons indicate your responses. The preferred responses are highlighted
For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
Indicate what changes(s) you will implement in your practice, if any, based on this CME course.
Submit a Comment

Multimedia

Some tools below are only available to our subscribers or users with an online account.

700 Views
0 Citations

Related Content

Customize your page view by dragging & repositioning the boxes below.

Articles Related By Topic
Related Collections
PubMed Articles
×