Non-melanocytic Skin Tumors
Moderator: Dr. Philip E. LeBoit
Case 2-1 -
A Lesson Ethical: Anatomy of Error and of Disclosure
Mark A. Hurt, MD
WCP Pathology PC
Maryland Heights (St. Louis) MO
Follicular Neoplasm, Germinative and Matrical
In the process of identifying cases to present at this conference, an interesting development occurred
and this is that story and its outcome.
In a computer search of cases with trichoblastic differentiation, I came across the following case:
a 27 year old black woman had had an excision of a nodular growth from the right posterior scalp in May,
2003. The specimen was removed via several shavings. Clinically, this lesion was thought to be a
melanocytic lesion vs. an adnexal tumor.
Case 2-1 - Slide 1
Microscopically, the lesion consisted of a dermal proliferation of basophilic cells with some degree
of pigmentation. The lobules were relatively uniform in size and they were composed of basophilic cells,
rather deeply basophilic, some of which were colonized by melanocytes, but many were not. Other areas
contained eosinophilic cells somewhat reminiscent of a faulty attempt to produce a hair filament, but
there were no shadow cells.
My diagnosis was trichoblastoma, large nodular type, pigmented.
In March, 2006, when I reviewed the case again, I discovered that there was actually more than just a
germ component to this lesion; there also seemed to be a matrical component to it. I now believed that
the diagnosis was incorrect and that this lesion was actually one composed of mixed components, including
germ and matrix. I still believed the lesion to be benign, but I believed also that the diagnosis needed
to be updated.
To this end, I notified the clinician. He requested that no change be made in the report because he
was concerned that the patient might be upset and might file a lawsuit for negligence. I then consulted
my attorney about whether I should report the findings anyway. My sense of it was that I should; after
all it was the honest thing to do, and there was no negligence involved. At the last minute, before
reporting on the lesion outside of the clinician's permission, the clinician called and told me to go
ahead and report the new findings because he had talked to the patient, and she was fine with it. At
that point I decided to send the case out for consultation because I thought that it was now important
for this case to have an external opinion and to try to relieve the internal struggle between the
clinician and me about the case. At the time, my differential diagnosis was between trichoblastoma and
matricoma, or a combination of the two, but the differential diagnosis included the trichoblastoma group
and the matricoma group, and perhaps panfolliculoma. Because I consider trichogerminoma to be a
variation of trichoblastoma, I did not consider that seriously, although I think some people might.
Historically, primary neoplasms of the hair follicle were written about as early as 1962, and in
Headington's and French's initial article on this topic (Arch Dermatol 1962; 86:430), they considered
germinal neoplasms to be "trichogenic adnexal tumors". "Trichomatrioma" was a lesion that contained
matrical components. There was, however, no lesion quite like the one seen here. Moreover, in Gray's
and Helwig's article on multiple and solitary trichoepithelioma in the Archives of Dermatology (1963;
87:102), they described lesions of the germ, but not the matrix, so these early descriptions did not fit
the present neoplasm either.
In 1970, Headington, writing in the Journal of Clinical Pathology, (1970; 23:464), identified a lesion
in his case #1 that he called trichoblastoma. One can look at this lesion today in his figure 2 and see
that it is not completely blastic, but it also contains matrix, and this lesion is probably the closest I
have seen thus far in the literature to the case in this presentation. It might be noted, also, that
Headington himself changed the name of the trichoblastoma in 1970 to "trichoblastic hamartoma" in 1976
(Am J Pathol 85:480). In that same article, Headington established one of the first global
classifications of follicular neoplasms in his description of a series of lesions that he termed
"trichoblastoma, trichoblastic fibroma, and trichogenic trichoblastoma"
Sau, et al, in 1992, writing in the Journal of Cutaneous Pathology (19:357) described lesions they
termed "trichogerminoma". These lesions also were fairly large, somewhat subcutaneous, and contained
many tightly packed "cell balls" of mostly germinal type epithelium. Matrix was not part of these
Writing in 2001, Ackerman, et. al., in their book on neoplasms with follicular differentiation,
integrated a deeper synthesis of follicular germinative neoplasms and combined theirs and previous
authors' views into one global designation of "trichoblastoma". Thus, the trichoblastoma, trichoblastic
fibroma, and trichogenic trichoblastoma of Headington were now combined all into one group, according to
Ackerman, et. al. The lesion closest to the one present in the present case is what Ackerman, et. al,
termed "large nodular trichoblastoma". The main difference between that kind of the lesion and the one
presented herein is the fact that there is matrical differentiation in the present case.
Ackerman, et al, writing also in that same text, identified mostly solid lobular neoplasms, termed
"matricoma", as lesions that are composed entirely of matrical epithelium and very little terminal
differentiation toward hair filaments, in contrast with classical pilomatricomas. Another lesion that
contained matrix, but also contained germ and terminal differentiation of follicles is one that Ackerman,
et al, described as panfolliculoma, also somewhat similar to the case presented herein. It is not,
however, exactly the same.
Thus, when I sent the case out for consultation, I sent it to A. Bernard Ackerman, M.D., because I
believed that he would have the best perspective on what this lesion might be. In my cover letter, I
explained that I thought that this lesion had both matrix and germinal components, but it didn't look
like any other lesion I had ever seen.
In his consultation letter, he stated "at higher magnification, however, it becomes apparent that this
neoplasm, benign by silhouette, is made up of aggregations composed of matrical cells primarily. In
addition to those cells, many of which are in mitosis and many of which are necrotic individually, there
is at the periphery, a rim of trichoblast (germative cells)…." In conclusion, Dr. Ackerman stated that
"In short, this patient has benign neoplasm made up mostly of matrical cells, but also follicular
"germative" cells." In his final sentence he stated that "In my experience this benign neoplasm is
Thus, this is an unusual follicular neoplasm with both follicular germ and matrix mixed together. I
present it here because of the diagnostic dilemma that it presented and because of the ethical dilemma
with which I was faced. As I understand it, to date the patient has had no regrowth of this lesion,
despite the fact that it was never removed in toto.