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LETTERS TO THE EDITOR

Is Melanocytic Matricoma a Bona Fide Entity or is it Just One Type of Matricoma?

Resnik, Kenneth S. M.D.

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The American Journal of Dermatopathology: April 2003 - Volume 25 - Issue 2 - p 166

To the Editor:

When reading an issue of a journal I usually do not refer to sources referenced, yet part of the discussion of an article about a neoplasm with follicular differentiation in the December 2002 issue of this journal compelled me to do just that. The lines that read, “The concept of matricoma as distinct from pilomatricoma was first put forth by Ackerman et al. in 1993, who did not, however, allude to the melanocytic colonization of such lesions” (1) struck me as odd because I distinctly remember hearing Bernie Ackerman saying many times during my fellowship training and subsequently at the multiheaded microscope that it is an expected finding in neoplasms with matrical and supramatrical differentiation to see an accompanying melanocytic proliferation. Faced with this discrepancy, I retrieved from my bookcase the source that was referenced, Ackerman's Neoplasms with Follicular Differentiation (2), turned to the chapter titled “Pilomatricoma and Matricoma” and found the following words on page 488:

“Just as melanocytes are associated intimately with matrical and supramatrical cells in the bulb of a normal hair follicle, so, too, melanocytes sometimes are seen among matrical and supramatrical cells in pilomatricoma. The number of melanocytes varies from few to many, their dendrites from short to long, and the melanin produced by them from scant to abundant.” (2)

Elsewhere in that chapter on page 500 it says the following about matricoma: “...we have come to recognize a benign neoplasm that contains all of the elements of a pilomatricoma, but whose silhouette is entirely different from that of pilomatricoma...the constituent cells...can be identified as matrical and supramatrical cells, identical to those of pilomatricoma...” (2)

In short, an increased number of melanocytes is one expected finding in neoplasms displaying matrical and supramatrical differentiation.

Furthermore, it appears that the presence of a melanocytic proliferation in a matricoma is the sole criterion for differentiating so-called melanocytic matricoma from matricoma (1,3). Readers of this journal should ask themselves if an expected and previously noted finding (2) is sufficient to consider a neoplasm as a distinct and unique entity. Just as a pigmented expression of squamous cell carcinoma is conceived of as one manifestation of squamous cell carcinoma that displays prominent dendritic melanocytes rather than a unique and distinctly different neoplasm, i.e., melanocytic squamous cell carcinoma, melanocytic matricoma should be conceived of as a variation on a theme rather than as an entity sui generis.

Kenneth S. Resnik, M.D.

REFERENCES

1. Rizzardi C, Brollo A, Colonna A, et al. A tumor with composite pilo-folliculosebaceous differentiation harboring a recently described new entity—melanocytic matricoma. Am J Dermatopathol 2002; 24:493–7.
2. Ackerman AB, DeViragh PA, Chongchitnant N. Pilomatricoma and matricoma. In: Neoplasms With Follicular Differentiation. Philadelphia: Lea & Febiger, 1993:477–506.
3. Carlson JA, Healy K, Slominski A, et al. Melanocytic matricoma: a report of two cases of a new entity. Am J Dermatopathol 1999; 21:344–9.
© 2003 Lippincott Williams & Wilkins, Inc.